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[PATCH 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow

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  [PATCH 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 16:10 +0200
    [PATCH v2 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 16:20 +0200
      [PATCH v3 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 16:30 +0200
    [PATCH 2/5] ipsec: check return value of skb_to_sgvec always "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 16:20 +0200
    [PATCH 4/5] macsec: check return value of skb_to_sgvec always "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 16:20 +0200
    Re: [PATCH 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to  prevent overflow David Miller <davem@davemloft.net> - 2017-04-25 16:50 +0200
      [PATCH v4 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 17:10 +0200
        Re: [PATCH v4 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to  prevent overflow David Miller <davem@davemloft.net> - 2017-04-25 17:20 +0200
          [PATCH v5 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 18:00 +0200
            [PATCH v5 3/5] rxrpc: check return value of skb_to_sgvec always "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 18:00 +0200
            [PATCH v5 4/5] macsec: check return value of skb_to_sgvec always "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 18:00 +0200
            [PATCH v5 2/5] ipsec: check return value of skb_to_sgvec always "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 18:00 +0200
            [PATCH v5 5/5] virtio_net: check return value of skb_to_sgvec always "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 18:00 +0200
            [PATCH v6 2/5] ipsec: check return value of skb_to_sgvec always "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 20:50 +0200
            [PATCH v6 4/5] macsec: check return value of skb_to_sgvec always "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 20:50 +0200
            [PATCH v6 5/5] virtio_net: check return value of skb_to_sgvec always "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 20:50 +0200
            [PATCH v6 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 20:50 +0200
              [PATCH v6 3/5] rxrpc: check return value of skb_to_sgvec always "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-25 20:50 +0200
                Re: [PATCH v6 3/5] rxrpc: check return value of skb_to_sgvec always Sabrina Dubroca <sd@queasysnail.net> - 2017-04-28 13:50 +0200
                  Re: [PATCH v6 3/5] rxrpc: check return value of skb_to_sgvec always "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-28 15:40 +0200
              Re: [PATCH v6 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to  prevent overflow "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-27 11:30 +0200
                Re: [PATCH v6 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to  prevent overflow Sabrina Dubroca <sd@queasysnail.net> - 2017-04-27 13:40 +0200
                  Re: [PATCH v6 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to  prevent overflow "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-27 14:10 +0200
                    RE: [PATCH v6 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to  prevent overflow David Laight <David.Laight@ACULAB.COM> - 2017-04-27 17:00 +0200
                Re: [PATCH v6 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to  prevent overflow David Miller <davem@davemloft.net> - 2017-04-27 18:00 +0200
              Re: [PATCH v6 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to  prevent overflow Sabrina Dubroca <sd@queasysnail.net> - 2017-04-28 18:20 +0200
                Re: [PATCH v6 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to  prevent overflow "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-29 00:50 +0200
    Re: [PATCH 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent  overflow Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> - 2017-04-25 17:50 +0200

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#1630539 — [PATCH 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow

This is a defense-in-depth measure in response to bugs like
4d6fa57b4dab0d77f4d8e9d9c73d1e63f6fe8fee.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 net/core/skbuff.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f86bf69cfb8d..3c2a7f323722 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3489,7 +3489,9 @@ void __init skb_init(void)
  *	@len: Length of buffer space to be mapped
  *
  *	Fill the specified scatter-gather list with mappings/pointers into a
- *	region of the buffer space attached to a socket buffer.
+ *	region of the buffer space attached to a socket buffer. Returns either
+ *	the number of scatterlist items used, or -EMSGSIZE if the contents
+ *	could not fit.
  */
 static int
 __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
@@ -3512,6 +3514,9 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 		int end;
 
+		if (elt && sg_is_last(&sg[elt - 1]))
+			return -EMSGSIZE;
+
 		WARN_ON(start > offset + len);
 
 		end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]);
@@ -3535,6 +3540,9 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 
 		WARN_ON(start > offset + len);
 
+		if (elt && sg_is_last(&sg[elt - 1]))
+			return -EMSGSIZE;
+
 		end = start + frag_iter->len;
 		if ((copy = end - offset) > 0) {
 			if (copy > len)
-- 
2.12.2

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#1630544 — [PATCH v2 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow

This is a defense-in-depth measure in response to bugs like
4d6fa57b4dab0d77f4d8e9d9c73d1e63f6fe8fee.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 net/core/skbuff.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f86bf69cfb8d..7ed2cdf54c0a 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3489,7 +3489,9 @@ void __init skb_init(void)
  *	@len: Length of buffer space to be mapped
  *
  *	Fill the specified scatter-gather list with mappings/pointers into a
- *	region of the buffer space attached to a socket buffer.
+ *	region of the buffer space attached to a socket buffer. Returns either
+ *	the number of scatterlist items used, or -EMSGSIZE if the contents
+ *	could not fit.
  */
 static int
 __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
@@ -3512,6 +3514,9 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 		int end;
 
+		if (elt && sg_is_last(&sg[elt - 1]))
+			return -EMSGSIZE;
+
 		WARN_ON(start > offset + len);
 
 		end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]);
@@ -3535,6 +3540,9 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 
 		WARN_ON(start > offset + len);
 
+		if (elt && sg_is_last(&sg[elt - 1]))
+			return -EMSGSIZE;
+
 		end = start + frag_iter->len;
 		if ((copy = end - offset) > 0) {
 			if (copy > len)
@@ -3581,6 +3589,9 @@ int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int le
 {
 	int nsg = __skb_to_sgvec(skb, sg, offset, len);
 
+	if (nsg < 0)
+		return nsg;
+
 	sg_mark_end(&sg[nsg - 1]);
 
 	return nsg;
-- 
2.12.2

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#1630556 — [PATCH v3 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow

This is a defense-in-depth measure in response to bugs like
4d6fa57b4dab0d77f4d8e9d9c73d1e63f6fe8fee.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
Sorry for the completely stupid amount of churn - v1,v2,v3 in the span of
two minutes. It's just that after noticing first that nsg needs to be checked,
I also noticed something a bit worse: that there was a bug (exploitable?) where
if skb_to_sgvec was called with empty values, there would be an out-of-bounds
write into sg[0 - 1]. So, this third (and hopefully final!) patch fixes that
bug while we're at it.

 net/core/skbuff.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f86bf69cfb8d..d103134deddb 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3489,7 +3489,9 @@ void __init skb_init(void)
  *	@len: Length of buffer space to be mapped
  *
  *	Fill the specified scatter-gather list with mappings/pointers into a
- *	region of the buffer space attached to a socket buffer.
+ *	region of the buffer space attached to a socket buffer. Returns either
+ *	the number of scatterlist items used, or -EMSGSIZE if the contents
+ *	could not fit.
  */
 static int
 __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
@@ -3512,6 +3514,9 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 		int end;
 
+		if (elt && sg_is_last(&sg[elt - 1]))
+			return -EMSGSIZE;
+
 		WARN_ON(start > offset + len);
 
 		end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]);
@@ -3535,6 +3540,9 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 
 		WARN_ON(start > offset + len);
 
+		if (elt && sg_is_last(&sg[elt - 1]))
+			return -EMSGSIZE;
+
 		end = start + frag_iter->len;
 		if ((copy = end - offset) > 0) {
 			if (copy > len)
@@ -3581,6 +3589,9 @@ int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int le
 {
 	int nsg = __skb_to_sgvec(skb, sg, offset, len);
 
+	if (nsg <= 0)
+		return nsg;
+
 	sg_mark_end(&sg[nsg - 1]);
 
 	return nsg;
-- 
2.12.2

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#1630550 — [PATCH 2/5] ipsec: check return value of skb_to_sgvec always

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 net/ipv4/ah4.c  |  8 ++++++--
 net/ipv4/esp4.c | 30 ++++++++++++++++++++----------
 net/ipv6/ah6.c  |  8 ++++++--
 net/ipv6/esp6.c | 31 +++++++++++++++++++++----------
 4 files changed, 53 insertions(+), 24 deletions(-)

diff --git a/net/ipv4/ah4.c b/net/ipv4/ah4.c
index 22377c8ff14b..e8f862358518 100644
--- a/net/ipv4/ah4.c
+++ b/net/ipv4/ah4.c
@@ -220,7 +220,9 @@ static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
 	ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
 
 	sg_init_table(sg, nfrags + sglists);
-	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out_free;
 
 	if (x->props.flags & XFRM_STATE_ESN) {
 		/* Attach seqhi sg right after packet payload */
@@ -393,7 +395,9 @@ static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 	skb_push(skb, ihl);
 
 	sg_init_table(sg, nfrags + sglists);
-	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out_free;
 
 	if (x->props.flags & XFRM_STATE_ESN) {
 		/* Attach seqhi sg right after packet payload */
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index b1e24446e297..42cb09cc8533 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -360,9 +360,13 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 			esph = esp_output_set_extra(skb, esph, extra);
 
 			sg_init_table(sg, nfrags);
-			skb_to_sgvec(skb, sg,
-				     (unsigned char *)esph - skb->data,
-				     assoclen + ivlen + clen + alen);
+			err = skb_to_sgvec(skb, sg,
+				           (unsigned char *)esph - skb->data,
+				           assoclen + ivlen + clen + alen);
+			if (unlikely(err < 0)) {
+				spin_unlock_bh(&x->lock);
+				goto error;
+			}
 
 			allocsize = ALIGN(skb->data_len, L1_CACHE_BYTES);
 
@@ -381,11 +385,13 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 			pfrag->offset = pfrag->offset + allocsize;
 
 			sg_init_table(dsg, skb_shinfo(skb)->nr_frags + 1);
-			skb_to_sgvec(skb, dsg,
-				     (unsigned char *)esph - skb->data,
-				     assoclen + ivlen + clen + alen);
+			err = skb_to_sgvec(skb, dsg,
+				           (unsigned char *)esph - skb->data,
+				           assoclen + ivlen + clen + alen);
 
 			spin_unlock_bh(&x->lock);
+			if (unlikely(err < 0))
+				goto error;
 
 			goto skip_cow2;
 		}
@@ -422,9 +428,11 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 	esph = esp_output_set_extra(skb, esph, extra);
 
 	sg_init_table(sg, nfrags);
-	skb_to_sgvec(skb, sg,
-		     (unsigned char *)esph - skb->data,
-		     assoclen + ivlen + clen + alen);
+	err = skb_to_sgvec(skb, sg,
+		           (unsigned char *)esph - skb->data,
+		           assoclen + ivlen + clen + alen);
+	if (unlikely(err < 0))
+		goto error;
 
 skip_cow2:
 	if ((x->props.flags & XFRM_STATE_ESN))
@@ -658,7 +666,9 @@ static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
 	esp_input_set_header(skb, seqhi);
 
 	sg_init_table(sg, nfrags);
-	skb_to_sgvec(skb, sg, 0, skb->len);
+	err = skb_to_sgvec(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out;
 
 	skb->ip_summed = CHECKSUM_NONE;
 
diff --git a/net/ipv6/ah6.c b/net/ipv6/ah6.c
index dda6035e3b84..755f38271dd5 100644
--- a/net/ipv6/ah6.c
+++ b/net/ipv6/ah6.c
@@ -423,7 +423,9 @@ static int ah6_output(struct xfrm_state *x, struct sk_buff *skb)
 	ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
 
 	sg_init_table(sg, nfrags + sglists);
-	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out_free;
 
 	if (x->props.flags & XFRM_STATE_ESN) {
 		/* Attach seqhi sg right after packet payload */
@@ -606,7 +608,9 @@ static int ah6_input(struct xfrm_state *x, struct sk_buff *skb)
 	ip6h->hop_limit   = 0;
 
 	sg_init_table(sg, nfrags + sglists);
-	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out_free;
 
 	if (x->props.flags & XFRM_STATE_ESN) {
 		/* Attach seqhi sg right after packet payload */
diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index ff54faa75631..017e2c2d36e1 100644
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -339,9 +339,13 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
 			esph = esp_output_set_esn(skb, esph, seqhi);
 
 			sg_init_table(sg, nfrags);
-			skb_to_sgvec(skb, sg,
-				     (unsigned char *)esph - skb->data,
-				     assoclen + ivlen + clen + alen);
+			err = skb_to_sgvec(skb, sg,
+				           (unsigned char *)esph - skb->data,
+				           assoclen + ivlen + clen + alen);
+			if (unlikely(err < 0)) {
+				spin_unlock_bh(&x->lock);
+				goto error;
+			}
 
 			allocsize = ALIGN(skb->data_len, L1_CACHE_BYTES);
 
@@ -360,12 +364,15 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
 			pfrag->offset = pfrag->offset + allocsize;
 
 			sg_init_table(dsg, skb_shinfo(skb)->nr_frags + 1);
-			skb_to_sgvec(skb, dsg,
-				     (unsigned char *)esph - skb->data,
-				     assoclen + ivlen + clen + alen);
+			err = skb_to_sgvec(skb, dsg,
+				           (unsigned char *)esph - skb->data,
+				           assoclen + ivlen + clen + alen);
 
 			spin_unlock_bh(&x->lock);
 
+			if (unlikely(err < 0))
+				goto error;
+
 			goto skip_cow2;
 		}
 	}
@@ -403,9 +410,11 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
 	esph = esp_output_set_esn(skb, esph, seqhi);
 
 	sg_init_table(sg, nfrags);
-	skb_to_sgvec(skb, sg,
-		     (unsigned char *)esph - skb->data,
-		     assoclen + ivlen + clen + alen);
+	err = skb_to_sgvec(skb, sg,
+		           (unsigned char *)esph - skb->data,
+		           assoclen + ivlen + clen + alen);
+	if (unlikely(err < 0))
+		goto error;
 
 skip_cow2:
 	if ((x->props.flags & XFRM_STATE_ESN))
@@ -600,7 +609,9 @@ static int esp6_input(struct xfrm_state *x, struct sk_buff *skb)
 	esp_input_set_header(skb, seqhi);
 
 	sg_init_table(sg, nfrags);
-	skb_to_sgvec(skb, sg, 0, skb->len);
+	ret = skb_to_sgvec(skb, sg, 0, skb->len);
+	if (unlikely(ret < 0))
+		goto out;
 
 	skb->ip_summed = CHECKSUM_NONE;
 
-- 
2.12.2

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#1630552 — [PATCH 4/5] macsec: check return value of skb_to_sgvec always

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 drivers/net/macsec.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index dbab05afcdbe..d846f42b99ec 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -733,7 +733,12 @@ static struct sk_buff *macsec_encrypt(struct sk_buff *skb,
 	macsec_fill_iv(iv, secy->sci, pn);
 
 	sg_init_table(sg, MAX_SKB_FRAGS + 1);
-	skb_to_sgvec(skb, sg, 0, skb->len);
+	ret = skb_to_sgvec(skb, sg, 0, skb->len);
+	if (unlikely(ret < 0)) {
+		macsec_txsa_put(tx_sa);
+		kfree_skb(skb);
+		return ERR_PTR(ret);
+	}
 
 	if (tx_sc->encrypt) {
 		int len = skb->len - macsec_hdr_len(sci_present) -
@@ -937,7 +942,11 @@ static struct sk_buff *macsec_decrypt(struct sk_buff *skb,
 	macsec_fill_iv(iv, sci, ntohl(hdr->packet_number));
 
 	sg_init_table(sg, MAX_SKB_FRAGS + 1);
-	skb_to_sgvec(skb, sg, 0, skb->len);
+	ret = skb_to_sgvec(skb, sg, 0, skb->len);
+	if (unlikely(ret < 0)) {
+		kfree_skb(skb);
+		return ERR_PTR(ret);
+	}
 
 	if (hdr->tci_an & MACSEC_TCI_E) {
 		/* confidentiality: ethernet + macsec header
-- 
2.12.2

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#1630572 — Re: [PATCH 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow

From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Tue, 25 Apr 2017 16:08:05 +0200

> This is a defense-in-depth measure in response to bugs like
> 4d6fa57b4dab0d77f4d8e9d9c73d1e63f6fe8fee.
> 
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Please refer to commits in the form:

$(SHA1_ID) ("Commit header line.")

That is, 12 bytes of SHA1_ID followed by the commit header line text
in both double quotes and parenthesis, like this:

4d6fa57b4dab ("macsec: avoid heap overflow in skb_to_sgvec")

Otherwise when changes get backported or applied to different trees,
they have different SHA1_ID values.  The commit header text removes
any and all ambiguity.

Thank you.

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#1630593 — [PATCH v4 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow

This is a defense-in-depth measure in response to bugs like
4d6fa57b4dab ("macsec: avoid heap overflow in skb_to_sgvec")

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
v4 fixes the commit message and moves the check into the inner-most if.

 net/core/skbuff.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f86bf69cfb8d..e75640006d78 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3489,7 +3489,9 @@ void __init skb_init(void)
  *	@len: Length of buffer space to be mapped
  *
  *	Fill the specified scatter-gather list with mappings/pointers into a
- *	region of the buffer space attached to a socket buffer.
+ *	region of the buffer space attached to a socket buffer. Returns either
+ *	the number of scatterlist items used, or -EMSGSIZE if the contents
+ *	could not fit.
  */
 static int
 __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
@@ -3517,6 +3519,8 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 		end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]);
 		if ((copy = end - offset) > 0) {
 			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+			if (elt && sg_is_last(&sg[elt - 1]))
+				return -EMSGSIZE;
 
 			if (copy > len)
 				copy = len;
@@ -3537,6 +3541,9 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 
 		end = start + frag_iter->len;
 		if ((copy = end - offset) > 0) {
+			if (elt && sg_is_last(&sg[elt - 1]))
+				return -EMSGSIZE;
+
 			if (copy > len)
 				copy = len;
 			elt += __skb_to_sgvec(frag_iter, sg+elt, offset - start,
@@ -3581,6 +3588,9 @@ int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int le
 {
 	int nsg = __skb_to_sgvec(skb, sg, offset, len);
 
+	if (nsg <= 0)
+		return nsg;
+
 	sg_mark_end(&sg[nsg - 1]);
 
 	return nsg;
-- 
2.12.2

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#1630627 — Re: [PATCH v4 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow

John this isn't how it works.

When you submit new versions of a patch that are part of a patch
series, you must resubmit the entire series not just the patches which
are changing.

Thanks.

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#1630720 — [PATCH v5 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow

This is a defense-in-depth measure in response to bugs like
4d6fa57b4dab ("macsec: avoid heap overflow in skb_to_sgvec")

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
This is a resend of v4 with all the other child commits along with it.

 net/core/skbuff.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f86bf69cfb8d..e75640006d78 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3489,7 +3489,9 @@ void __init skb_init(void)
  *	@len: Length of buffer space to be mapped
  *
  *	Fill the specified scatter-gather list with mappings/pointers into a
- *	region of the buffer space attached to a socket buffer.
+ *	region of the buffer space attached to a socket buffer. Returns either
+ *	the number of scatterlist items used, or -EMSGSIZE if the contents
+ *	could not fit.
  */
 static int
 __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
@@ -3517,6 +3519,8 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 		end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]);
 		if ((copy = end - offset) > 0) {
 			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+			if (elt && sg_is_last(&sg[elt - 1]))
+				return -EMSGSIZE;
 
 			if (copy > len)
 				copy = len;
@@ -3537,6 +3541,9 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 
 		end = start + frag_iter->len;
 		if ((copy = end - offset) > 0) {
+			if (elt && sg_is_last(&sg[elt - 1]))
+				return -EMSGSIZE;
+
 			if (copy > len)
 				copy = len;
 			elt += __skb_to_sgvec(frag_iter, sg+elt, offset - start,
@@ -3581,6 +3588,9 @@ int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int le
 {
 	int nsg = __skb_to_sgvec(skb, sg, offset, len);
 
+	if (nsg <= 0)
+		return nsg;
+
 	sg_mark_end(&sg[nsg - 1]);
 
 	return nsg;
-- 
2.12.2

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#1630722 — [PATCH v5 3/5] rxrpc: check return value of skb_to_sgvec always

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 net/rxrpc/rxkad.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/rxrpc/rxkad.c b/net/rxrpc/rxkad.c
index 4374e7b9c7bf..dcf46c9c3ece 100644
--- a/net/rxrpc/rxkad.c
+++ b/net/rxrpc/rxkad.c
@@ -229,7 +229,9 @@ static int rxkad_secure_packet_encrypt(const struct rxrpc_call *call,
 	len &= ~(call->conn->size_align - 1);
 
 	sg_init_table(sg, nsg);
-	skb_to_sgvec(skb, sg, 0, len);
+	err = skb_to_sgvec(skb, sg, 0, len);
+	if (unlikely(err < 0))
+		goto out;
 	skcipher_request_set_crypt(req, sg, sg, len, iv.x);
 	crypto_skcipher_encrypt(req);
 
@@ -342,7 +344,8 @@ static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb,
 		goto nomem;
 
 	sg_init_table(sg, nsg);
-	skb_to_sgvec(skb, sg, offset, 8);
+	if (unlikely(skb_to_sgvec(skb, sg, offset, 8) < 0))
+		goto nomem;
 
 	/* start the decryption afresh */
 	memset(&iv, 0, sizeof(iv));
@@ -429,7 +432,8 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb,
 	}
 
 	sg_init_table(sg, nsg);
-	skb_to_sgvec(skb, sg, offset, len);
+	if (unlikely(skb_to_sgvec(skb, sg, offset, len) < 0))
+		goto nomem;
 
 	/* decrypt from the session key */
 	token = call->conn->params.key->payload.data[0];
-- 
2.12.2

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#1630724 — [PATCH v5 4/5] macsec: check return value of skb_to_sgvec always

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 drivers/net/macsec.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index dbab05afcdbe..d846f42b99ec 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -733,7 +733,12 @@ static struct sk_buff *macsec_encrypt(struct sk_buff *skb,
 	macsec_fill_iv(iv, secy->sci, pn);
 
 	sg_init_table(sg, MAX_SKB_FRAGS + 1);
-	skb_to_sgvec(skb, sg, 0, skb->len);
+	ret = skb_to_sgvec(skb, sg, 0, skb->len);
+	if (unlikely(ret < 0)) {
+		macsec_txsa_put(tx_sa);
+		kfree_skb(skb);
+		return ERR_PTR(ret);
+	}
 
 	if (tx_sc->encrypt) {
 		int len = skb->len - macsec_hdr_len(sci_present) -
@@ -937,7 +942,11 @@ static struct sk_buff *macsec_decrypt(struct sk_buff *skb,
 	macsec_fill_iv(iv, sci, ntohl(hdr->packet_number));
 
 	sg_init_table(sg, MAX_SKB_FRAGS + 1);
-	skb_to_sgvec(skb, sg, 0, skb->len);
+	ret = skb_to_sgvec(skb, sg, 0, skb->len);
+	if (unlikely(ret < 0)) {
+		kfree_skb(skb);
+		return ERR_PTR(ret);
+	}
 
 	if (hdr->tci_an & MACSEC_TCI_E) {
 		/* confidentiality: ethernet + macsec header
-- 
2.12.2

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#1630725 — [PATCH v5 2/5] ipsec: check return value of skb_to_sgvec always

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 net/ipv4/ah4.c  |  8 ++++++--
 net/ipv4/esp4.c | 30 ++++++++++++++++++++----------
 net/ipv6/ah6.c  |  8 ++++++--
 net/ipv6/esp6.c | 31 +++++++++++++++++++++----------
 4 files changed, 53 insertions(+), 24 deletions(-)

diff --git a/net/ipv4/ah4.c b/net/ipv4/ah4.c
index 22377c8ff14b..e8f862358518 100644
--- a/net/ipv4/ah4.c
+++ b/net/ipv4/ah4.c
@@ -220,7 +220,9 @@ static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
 	ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
 
 	sg_init_table(sg, nfrags + sglists);
-	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out_free;
 
 	if (x->props.flags & XFRM_STATE_ESN) {
 		/* Attach seqhi sg right after packet payload */
@@ -393,7 +395,9 @@ static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 	skb_push(skb, ihl);
 
 	sg_init_table(sg, nfrags + sglists);
-	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out_free;
 
 	if (x->props.flags & XFRM_STATE_ESN) {
 		/* Attach seqhi sg right after packet payload */
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index b1e24446e297..42cb09cc8533 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -360,9 +360,13 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 			esph = esp_output_set_extra(skb, esph, extra);
 
 			sg_init_table(sg, nfrags);
-			skb_to_sgvec(skb, sg,
-				     (unsigned char *)esph - skb->data,
-				     assoclen + ivlen + clen + alen);
+			err = skb_to_sgvec(skb, sg,
+				           (unsigned char *)esph - skb->data,
+				           assoclen + ivlen + clen + alen);
+			if (unlikely(err < 0)) {
+				spin_unlock_bh(&x->lock);
+				goto error;
+			}
 
 			allocsize = ALIGN(skb->data_len, L1_CACHE_BYTES);
 
@@ -381,11 +385,13 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 			pfrag->offset = pfrag->offset + allocsize;
 
 			sg_init_table(dsg, skb_shinfo(skb)->nr_frags + 1);
-			skb_to_sgvec(skb, dsg,
-				     (unsigned char *)esph - skb->data,
-				     assoclen + ivlen + clen + alen);
+			err = skb_to_sgvec(skb, dsg,
+				           (unsigned char *)esph - skb->data,
+				           assoclen + ivlen + clen + alen);
 
 			spin_unlock_bh(&x->lock);
+			if (unlikely(err < 0))
+				goto error;
 
 			goto skip_cow2;
 		}
@@ -422,9 +428,11 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 	esph = esp_output_set_extra(skb, esph, extra);
 
 	sg_init_table(sg, nfrags);
-	skb_to_sgvec(skb, sg,
-		     (unsigned char *)esph - skb->data,
-		     assoclen + ivlen + clen + alen);
+	err = skb_to_sgvec(skb, sg,
+		           (unsigned char *)esph - skb->data,
+		           assoclen + ivlen + clen + alen);
+	if (unlikely(err < 0))
+		goto error;
 
 skip_cow2:
 	if ((x->props.flags & XFRM_STATE_ESN))
@@ -658,7 +666,9 @@ static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
 	esp_input_set_header(skb, seqhi);
 
 	sg_init_table(sg, nfrags);
-	skb_to_sgvec(skb, sg, 0, skb->len);
+	err = skb_to_sgvec(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out;
 
 	skb->ip_summed = CHECKSUM_NONE;
 
diff --git a/net/ipv6/ah6.c b/net/ipv6/ah6.c
index dda6035e3b84..755f38271dd5 100644
--- a/net/ipv6/ah6.c
+++ b/net/ipv6/ah6.c
@@ -423,7 +423,9 @@ static int ah6_output(struct xfrm_state *x, struct sk_buff *skb)
 	ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
 
 	sg_init_table(sg, nfrags + sglists);
-	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out_free;
 
 	if (x->props.flags & XFRM_STATE_ESN) {
 		/* Attach seqhi sg right after packet payload */
@@ -606,7 +608,9 @@ static int ah6_input(struct xfrm_state *x, struct sk_buff *skb)
 	ip6h->hop_limit   = 0;
 
 	sg_init_table(sg, nfrags + sglists);
-	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out_free;
 
 	if (x->props.flags & XFRM_STATE_ESN) {
 		/* Attach seqhi sg right after packet payload */
diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index ff54faa75631..017e2c2d36e1 100644
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -339,9 +339,13 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
 			esph = esp_output_set_esn(skb, esph, seqhi);
 
 			sg_init_table(sg, nfrags);
-			skb_to_sgvec(skb, sg,
-				     (unsigned char *)esph - skb->data,
-				     assoclen + ivlen + clen + alen);
+			err = skb_to_sgvec(skb, sg,
+				           (unsigned char *)esph - skb->data,
+				           assoclen + ivlen + clen + alen);
+			if (unlikely(err < 0)) {
+				spin_unlock_bh(&x->lock);
+				goto error;
+			}
 
 			allocsize = ALIGN(skb->data_len, L1_CACHE_BYTES);
 
@@ -360,12 +364,15 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
 			pfrag->offset = pfrag->offset + allocsize;
 
 			sg_init_table(dsg, skb_shinfo(skb)->nr_frags + 1);
-			skb_to_sgvec(skb, dsg,
-				     (unsigned char *)esph - skb->data,
-				     assoclen + ivlen + clen + alen);
+			err = skb_to_sgvec(skb, dsg,
+				           (unsigned char *)esph - skb->data,
+				           assoclen + ivlen + clen + alen);
 
 			spin_unlock_bh(&x->lock);
 
+			if (unlikely(err < 0))
+				goto error;
+
 			goto skip_cow2;
 		}
 	}
@@ -403,9 +410,11 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
 	esph = esp_output_set_esn(skb, esph, seqhi);
 
 	sg_init_table(sg, nfrags);
-	skb_to_sgvec(skb, sg,
-		     (unsigned char *)esph - skb->data,
-		     assoclen + ivlen + clen + alen);
+	err = skb_to_sgvec(skb, sg,
+		           (unsigned char *)esph - skb->data,
+		           assoclen + ivlen + clen + alen);
+	if (unlikely(err < 0))
+		goto error;
 
 skip_cow2:
 	if ((x->props.flags & XFRM_STATE_ESN))
@@ -600,7 +609,9 @@ static int esp6_input(struct xfrm_state *x, struct sk_buff *skb)
 	esp_input_set_header(skb, seqhi);
 
 	sg_init_table(sg, nfrags);
-	skb_to_sgvec(skb, sg, 0, skb->len);
+	ret = skb_to_sgvec(skb, sg, 0, skb->len);
+	if (unlikely(ret < 0))
+		goto out;
 
 	skb->ip_summed = CHECKSUM_NONE;
 
-- 
2.12.2

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#1630730 — [PATCH v5 5/5] virtio_net: check return value of skb_to_sgvec always

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 drivers/net/virtio_net.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index f36584616e7d..1709fd0b4bf7 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1081,7 +1081,7 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
 	struct virtio_net_hdr_mrg_rxbuf *hdr;
 	const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
 	struct virtnet_info *vi = sq->vq->vdev->priv;
-	unsigned num_sg;
+	int num_sg;
 	unsigned hdr_len = vi->hdr_len;
 	bool can_push;
 
@@ -1114,6 +1114,8 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
 		sg_set_buf(sq->sg, hdr, hdr_len);
 		num_sg = skb_to_sgvec(skb, sq->sg + 1, 0, skb->len) + 1;
 	}
+	if (unlikely(num_sg < 0))
+		return num_sg;
 	return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, skb, GFP_ATOMIC);
 }
 
-- 
2.12.2

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#1630902 — [PATCH v6 2/5] ipsec: check return value of skb_to_sgvec always

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 net/ipv4/ah4.c  |  8 ++++++--
 net/ipv4/esp4.c | 30 ++++++++++++++++++++----------
 net/ipv6/ah6.c  |  8 ++++++--
 net/ipv6/esp6.c | 31 +++++++++++++++++++++----------
 4 files changed, 53 insertions(+), 24 deletions(-)

diff --git a/net/ipv4/ah4.c b/net/ipv4/ah4.c
index 22377c8ff14b..e8f862358518 100644
--- a/net/ipv4/ah4.c
+++ b/net/ipv4/ah4.c
@@ -220,7 +220,9 @@ static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
 	ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
 
 	sg_init_table(sg, nfrags + sglists);
-	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out_free;
 
 	if (x->props.flags & XFRM_STATE_ESN) {
 		/* Attach seqhi sg right after packet payload */
@@ -393,7 +395,9 @@ static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 	skb_push(skb, ihl);
 
 	sg_init_table(sg, nfrags + sglists);
-	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out_free;
 
 	if (x->props.flags & XFRM_STATE_ESN) {
 		/* Attach seqhi sg right after packet payload */
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index b1e24446e297..42cb09cc8533 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -360,9 +360,13 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 			esph = esp_output_set_extra(skb, esph, extra);
 
 			sg_init_table(sg, nfrags);
-			skb_to_sgvec(skb, sg,
-				     (unsigned char *)esph - skb->data,
-				     assoclen + ivlen + clen + alen);
+			err = skb_to_sgvec(skb, sg,
+				           (unsigned char *)esph - skb->data,
+				           assoclen + ivlen + clen + alen);
+			if (unlikely(err < 0)) {
+				spin_unlock_bh(&x->lock);
+				goto error;
+			}
 
 			allocsize = ALIGN(skb->data_len, L1_CACHE_BYTES);
 
@@ -381,11 +385,13 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 			pfrag->offset = pfrag->offset + allocsize;
 
 			sg_init_table(dsg, skb_shinfo(skb)->nr_frags + 1);
-			skb_to_sgvec(skb, dsg,
-				     (unsigned char *)esph - skb->data,
-				     assoclen + ivlen + clen + alen);
+			err = skb_to_sgvec(skb, dsg,
+				           (unsigned char *)esph - skb->data,
+				           assoclen + ivlen + clen + alen);
 
 			spin_unlock_bh(&x->lock);
+			if (unlikely(err < 0))
+				goto error;
 
 			goto skip_cow2;
 		}
@@ -422,9 +428,11 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 	esph = esp_output_set_extra(skb, esph, extra);
 
 	sg_init_table(sg, nfrags);
-	skb_to_sgvec(skb, sg,
-		     (unsigned char *)esph - skb->data,
-		     assoclen + ivlen + clen + alen);
+	err = skb_to_sgvec(skb, sg,
+		           (unsigned char *)esph - skb->data,
+		           assoclen + ivlen + clen + alen);
+	if (unlikely(err < 0))
+		goto error;
 
 skip_cow2:
 	if ((x->props.flags & XFRM_STATE_ESN))
@@ -658,7 +666,9 @@ static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
 	esp_input_set_header(skb, seqhi);
 
 	sg_init_table(sg, nfrags);
-	skb_to_sgvec(skb, sg, 0, skb->len);
+	err = skb_to_sgvec(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out;
 
 	skb->ip_summed = CHECKSUM_NONE;
 
diff --git a/net/ipv6/ah6.c b/net/ipv6/ah6.c
index dda6035e3b84..755f38271dd5 100644
--- a/net/ipv6/ah6.c
+++ b/net/ipv6/ah6.c
@@ -423,7 +423,9 @@ static int ah6_output(struct xfrm_state *x, struct sk_buff *skb)
 	ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
 
 	sg_init_table(sg, nfrags + sglists);
-	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out_free;
 
 	if (x->props.flags & XFRM_STATE_ESN) {
 		/* Attach seqhi sg right after packet payload */
@@ -606,7 +608,9 @@ static int ah6_input(struct xfrm_state *x, struct sk_buff *skb)
 	ip6h->hop_limit   = 0;
 
 	sg_init_table(sg, nfrags + sglists);
-	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
+	if (unlikely(err < 0))
+		goto out_free;
 
 	if (x->props.flags & XFRM_STATE_ESN) {
 		/* Attach seqhi sg right after packet payload */
diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index ff54faa75631..017e2c2d36e1 100644
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -339,9 +339,13 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
 			esph = esp_output_set_esn(skb, esph, seqhi);
 
 			sg_init_table(sg, nfrags);
-			skb_to_sgvec(skb, sg,
-				     (unsigned char *)esph - skb->data,
-				     assoclen + ivlen + clen + alen);
+			err = skb_to_sgvec(skb, sg,
+				           (unsigned char *)esph - skb->data,
+				           assoclen + ivlen + clen + alen);
+			if (unlikely(err < 0)) {
+				spin_unlock_bh(&x->lock);
+				goto error;
+			}
 
 			allocsize = ALIGN(skb->data_len, L1_CACHE_BYTES);
 
@@ -360,12 +364,15 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
 			pfrag->offset = pfrag->offset + allocsize;
 
 			sg_init_table(dsg, skb_shinfo(skb)->nr_frags + 1);
-			skb_to_sgvec(skb, dsg,
-				     (unsigned char *)esph - skb->data,
-				     assoclen + ivlen + clen + alen);
+			err = skb_to_sgvec(skb, dsg,
+				           (unsigned char *)esph - skb->data,
+				           assoclen + ivlen + clen + alen);
 
 			spin_unlock_bh(&x->lock);
 
+			if (unlikely(err < 0))
+				goto error;
+
 			goto skip_cow2;
 		}
 	}
@@ -403,9 +410,11 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
 	esph = esp_output_set_esn(skb, esph, seqhi);
 
 	sg_init_table(sg, nfrags);
-	skb_to_sgvec(skb, sg,
-		     (unsigned char *)esph - skb->data,
-		     assoclen + ivlen + clen + alen);
+	err = skb_to_sgvec(skb, sg,
+		           (unsigned char *)esph - skb->data,
+		           assoclen + ivlen + clen + alen);
+	if (unlikely(err < 0))
+		goto error;
 
 skip_cow2:
 	if ((x->props.flags & XFRM_STATE_ESN))
@@ -600,7 +609,9 @@ static int esp6_input(struct xfrm_state *x, struct sk_buff *skb)
 	esp_input_set_header(skb, seqhi);
 
 	sg_init_table(sg, nfrags);
-	skb_to_sgvec(skb, sg, 0, skb->len);
+	ret = skb_to_sgvec(skb, sg, 0, skb->len);
+	if (unlikely(ret < 0))
+		goto out;
 
 	skb->ip_summed = CHECKSUM_NONE;
 
-- 
2.12.2

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#1630903 — [PATCH v6 4/5] macsec: check return value of skb_to_sgvec always

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 drivers/net/macsec.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index dbab05afcdbe..d846f42b99ec 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -733,7 +733,12 @@ static struct sk_buff *macsec_encrypt(struct sk_buff *skb,
 	macsec_fill_iv(iv, secy->sci, pn);
 
 	sg_init_table(sg, MAX_SKB_FRAGS + 1);
-	skb_to_sgvec(skb, sg, 0, skb->len);
+	ret = skb_to_sgvec(skb, sg, 0, skb->len);
+	if (unlikely(ret < 0)) {
+		macsec_txsa_put(tx_sa);
+		kfree_skb(skb);
+		return ERR_PTR(ret);
+	}
 
 	if (tx_sc->encrypt) {
 		int len = skb->len - macsec_hdr_len(sci_present) -
@@ -937,7 +942,11 @@ static struct sk_buff *macsec_decrypt(struct sk_buff *skb,
 	macsec_fill_iv(iv, sci, ntohl(hdr->packet_number));
 
 	sg_init_table(sg, MAX_SKB_FRAGS + 1);
-	skb_to_sgvec(skb, sg, 0, skb->len);
+	ret = skb_to_sgvec(skb, sg, 0, skb->len);
+	if (unlikely(ret < 0)) {
+		kfree_skb(skb);
+		return ERR_PTR(ret);
+	}
 
 	if (hdr->tci_an & MACSEC_TCI_E) {
 		/* confidentiality: ethernet + macsec header
-- 
2.12.2

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#1630905 — [PATCH v6 5/5] virtio_net: check return value of skb_to_sgvec always

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 drivers/net/virtio_net.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index f36584616e7d..1709fd0b4bf7 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1081,7 +1081,7 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
 	struct virtio_net_hdr_mrg_rxbuf *hdr;
 	const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
 	struct virtnet_info *vi = sq->vq->vdev->priv;
-	unsigned num_sg;
+	int num_sg;
 	unsigned hdr_len = vi->hdr_len;
 	bool can_push;
 
@@ -1114,6 +1114,8 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
 		sg_set_buf(sq->sg, hdr, hdr_len);
 		num_sg = skb_to_sgvec(skb, sq->sg + 1, 0, skb->len) + 1;
 	}
+	if (unlikely(num_sg < 0))
+		return num_sg;
 	return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, skb, GFP_ATOMIC);
 }
 
-- 
2.12.2

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#1630907 — [PATCH v6 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow

This is a defense-in-depth measure in response to bugs like
4d6fa57b4dab ("macsec: avoid heap overflow in skb_to_sgvec"). While
we're at it, we also limit the amount of recursion this function is
allowed to do. Not actually providing a bounded base case is a future
diaster that we can easily avoid here.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
Changes v5->v6:
  * Use unlikely() for the rare overflow conditions.
  * Also bound recursion, since this is a potential disaster we can avert.

 net/core/skbuff.c | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f86bf69cfb8d..24fb53f8534e 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3489,16 +3489,22 @@ void __init skb_init(void)
  *	@len: Length of buffer space to be mapped
  *
  *	Fill the specified scatter-gather list with mappings/pointers into a
- *	region of the buffer space attached to a socket buffer.
+ *	region of the buffer space attached to a socket buffer. Returns either
+ *	the number of scatterlist items used, or -EMSGSIZE if the contents
+ *	could not fit.
  */
 static int
-__skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
+__skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len,
+	       unsigned int recursion_level)
 {
 	int start = skb_headlen(skb);
 	int i, copy = start - offset;
 	struct sk_buff *frag_iter;
 	int elt = 0;
 
+	if (unlikely(recursion_level >= 32))
+		return -EMSGSIZE;
+
 	if (copy > 0) {
 		if (copy > len)
 			copy = len;
@@ -3517,6 +3523,8 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 		end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]);
 		if ((copy = end - offset) > 0) {
 			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+			if (unlikely(elt && sg_is_last(&sg[elt - 1])))
+				return -EMSGSIZE;
 
 			if (copy > len)
 				copy = len;
@@ -3531,16 +3539,22 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 	}
 
 	skb_walk_frags(skb, frag_iter) {
-		int end;
+		int end, ret;
 
 		WARN_ON(start > offset + len);
 
 		end = start + frag_iter->len;
 		if ((copy = end - offset) > 0) {
+			if (unlikely(elt && sg_is_last(&sg[elt - 1])))
+				return -EMSGSIZE;
+
 			if (copy > len)
 				copy = len;
-			elt += __skb_to_sgvec(frag_iter, sg+elt, offset - start,
-					      copy);
+			ret = __skb_to_sgvec(frag_iter, sg+elt, offset - start,
+					      copy, recursion_level + 1);
+			if (unlikely(ret < 0))
+				return ret;
+			elt += ret;
 			if ((len -= copy) == 0)
 				return elt;
 			offset += copy;
@@ -3573,13 +3587,16 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 int skb_to_sgvec_nomark(struct sk_buff *skb, struct scatterlist *sg,
 			int offset, int len)
 {
-	return __skb_to_sgvec(skb, sg, offset, len);
+	return __skb_to_sgvec(skb, sg, offset, len, 0);
 }
 EXPORT_SYMBOL_GPL(skb_to_sgvec_nomark);
 
 int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 {
-	int nsg = __skb_to_sgvec(skb, sg, offset, len);
+	int nsg = __skb_to_sgvec(skb, sg, offset, len, 0);
+
+	if (nsg <= 0)
+		return nsg;
 
 	sg_mark_end(&sg[nsg - 1]);
 
-- 
2.12.2

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#1630909 — [PATCH v6 3/5] rxrpc: check return value of skb_to_sgvec always

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 net/rxrpc/rxkad.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/rxrpc/rxkad.c b/net/rxrpc/rxkad.c
index 4374e7b9c7bf..dcf46c9c3ece 100644
--- a/net/rxrpc/rxkad.c
+++ b/net/rxrpc/rxkad.c
@@ -229,7 +229,9 @@ static int rxkad_secure_packet_encrypt(const struct rxrpc_call *call,
 	len &= ~(call->conn->size_align - 1);
 
 	sg_init_table(sg, nsg);
-	skb_to_sgvec(skb, sg, 0, len);
+	err = skb_to_sgvec(skb, sg, 0, len);
+	if (unlikely(err < 0))
+		goto out;
 	skcipher_request_set_crypt(req, sg, sg, len, iv.x);
 	crypto_skcipher_encrypt(req);
 
@@ -342,7 +344,8 @@ static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb,
 		goto nomem;
 
 	sg_init_table(sg, nsg);
-	skb_to_sgvec(skb, sg, offset, 8);
+	if (unlikely(skb_to_sgvec(skb, sg, offset, 8) < 0))
+		goto nomem;
 
 	/* start the decryption afresh */
 	memset(&iv, 0, sizeof(iv));
@@ -429,7 +432,8 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb,
 	}
 
 	sg_init_table(sg, nsg);
-	skb_to_sgvec(skb, sg, offset, len);
+	if (unlikely(skb_to_sgvec(skb, sg, offset, len) < 0))
+		goto nomem;
 
 	/* decrypt from the session key */
 	token = call->conn->params.key->payload.data[0];
-- 
2.12.2

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#1632814 — Re: [PATCH v6 3/5] rxrpc: check return value of skb_to_sgvec always

2017-04-25, 20:47:32 +0200, Jason A. Donenfeld wrote:
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
>  net/rxrpc/rxkad.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/net/rxrpc/rxkad.c b/net/rxrpc/rxkad.c
> index 4374e7b9c7bf..dcf46c9c3ece 100644
> --- a/net/rxrpc/rxkad.c
> +++ b/net/rxrpc/rxkad.c
[...]
> @@ -429,7 +432,8 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb,
>  	}
>  

Adding a few more lines of context:

	sg = _sg;
	if (unlikely(nsg > 4)) {
		sg = kmalloc(sizeof(*sg) * nsg, GFP_NOIO);
		if (!sg)
			goto nomem;
	}

>  	sg_init_table(sg, nsg);
> -	skb_to_sgvec(skb, sg, offset, len);
> +	if (unlikely(skb_to_sgvec(skb, sg, offset, len) < 0))
> +		goto nomem;

You're leaking sg when nsg > 4, you'll need to add this:

	if (sg != _sg)
		kfree(sg);



BTW, when you resubmit, please Cc: the maintainers of the files you're
changing for each patch, so that they can review this stuff. And send
patch 1 to all of them, otherwise they might be surprised that we even
need <0 checking after calls to skb_to_sgvec.

You might also want to add a cover letter.

-- 
Sabrina

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#1632881 — Re: [PATCH v6 3/5] rxrpc: check return value of skb_to_sgvec always

Hi Sabrina,

Thanks for the review.

On Fri, Apr 28, 2017 at 1:41 PM, Sabrina Dubroca <sd@queasysnail.net> wrote:
> >       sg_init_table(sg, nsg);
> > -     skb_to_sgvec(skb, sg, offset, len);
> > +     if (unlikely(skb_to_sgvec(skb, sg, offset, len) < 0))
> > +             goto nomem;
>
> You're leaking sg when nsg > 4, you'll need to add this:
>
>         if (sg != _sg)
>                 kfree(sg);

Nice catch. I'll fix this up in the next revision.


>
>
>
> BTW, when you resubmit, please Cc: the maintainers of the files you're
> changing for each patch, so that they can review this stuff. And send
> patch 1 to all of them, otherwise they might be surprised that we even
> need <0 checking after calls to skb_to_sgvec.
>
> You might also want to add a cover letter.

Both good ideas. Will do.

Jason

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