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[PATCH 4.11 011/115] tcp: avoid fragmenting peculiar skbs in SACK

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4.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yuchung Cheng <ycheng@google.com>


[ Upstream commit b451e5d24ba6687c6f0e7319c727a709a1846c06 ]

This patch fixes a bug in splitting an SKB during SACK
processing. Specifically if an skb contains multiple
packets and is only partially sacked in the higher sequences,
tcp_match_sack_to_skb() splits the skb and marks the second fragment
as SACKed.

The current code further attempts rounding up the first fragment
to MSS boundaries. But it misses a boundary condition when the
rounded-up fragment size (pkt_len) is exactly skb size.  Spliting
such an skb is pointless and causses a kernel warning and aborts
the SACK processing. This patch universally checks such over-split
before calling tcp_fragment to prevent these unnecessary warnings.

Fixes: adb92db857ee ("tcp: Make SACK code to split only at mss boundaries")
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/tcp_input.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1174,13 +1174,14 @@ static int tcp_match_skb_to_sack(struct
 		 */
 		if (pkt_len > mss) {
 			unsigned int new_len = (pkt_len / mss) * mss;
-			if (!in_sack && new_len < pkt_len) {
+			if (!in_sack && new_len < pkt_len)
 				new_len += mss;
-				if (new_len >= skb->len)
-					return 0;
-			}
 			pkt_len = new_len;
 		}
+
+		if (pkt_len >= skb->len && !in_sack)
+			return 0;
+
 		err = tcp_fragment(sk, skb, pkt_len, mss, GFP_ATOMIC);
 		if (err < 0)
 			return err;

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[PATCH 4.11 000/115] 4.11.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 033/115] virtio-net: enable TSO/checksum offloads for Q-in-Q vlans Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 011/115] tcp: avoid fragmenting peculiar skbs in SACK Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 003/115] ipv6/dccp: do not inherit ipv6_mc_list from parent Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 009/115] netem: fix skb_orphan_partial() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 023/115] ipv6: Check ip6_find_1stfragopt() return value properly. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 001/115] dccp/tcp: do not inherit mc_list from parent Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 018/115] tcp: eliminate negative reordering in tcp_clean_rtx_queue Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 024/115] bridge: netlink: check vlan_default_pvid range Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 027/115] ipv6: fix out of bound writes in __ip6_append_data() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 017/115] net/mlx5e: Fix ethtool pause support and advertise reporting Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 029/115] net/mlx5: Avoid using pending command interface slots Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 021/115] net: Improve handling of failures on link and route dumps Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 008/115] bpf, arm64: fix faulty emission of map access in tail calls Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 012/115] tipc: make macro tipc_wait_for_cond() smp safe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 043/115] sparc: Fix -Wstringop-overflow warning Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 005/115] s390/qeth: unbreak OSM and OSN support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 007/115] s390/qeth: add missing hash table initializations Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 004/115] s390/qeth: handle sysfs error during initialization Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  [PATCH 4.11 020/115] net/smc: Add warning about remote memory exposure Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-05 19:00 +0200
  Re: [PATCH 4.11 000/115] 4.11.4-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-06-05 22:40 +0200
    Re: [PATCH 4.11 000/115] 4.11.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-06 09:30 +0200
  Re: [PATCH 4.11 000/115] 4.11.4-stable review Guenter Roeck <linux@roeck-us.net> - 2017-06-06 00:30 +0200
    Re: [PATCH 4.11 000/115] 4.11.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-06 09:30 +0200

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