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[PATCH 4.10 42/69] make skb_copy_datagram_msg() et.al. preserve ->msg_iter on error

From Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups linux.kernel
Subject [PATCH 4.10 42/69] make skb_copy_datagram_msg() et.al. preserve ->msg_iter on error
Date 2017-04-19 16:50 +0200
Message-ID <txZ5E-4CC-11@gated-at.bofh.it> (permalink)
References <txYVX-4yJ-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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

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

From: Al Viro <viro@zeniv.linux.org.uk>

commit 3278682123811dd8ef07de5eb701fc4548fcebf2 upstream.

Fixes the mess observed in e.g. rsync over a noisy link we'd been
seeing since last Summer.  What happens is that we copy part of
a datagram before noticing a checksum mismatch.  Datagram will be
resent, all right, but we want the next try go into the same place,
not after it...

All this family of primitives (copy/checksum and copy a datagram
into destination) is "all or nothing" sort of interface - either
we get 0 (meaning that copy had been successful) or we get an
error (and no way to tell how much had been copied before we ran
into whatever error it had been).  Make all of them leave iterator
unadvanced in case of errors - all callers must be able to cope
with that (an error might've been caught before the iterator had
been advanced), it costs very little to arrange, it's safer for
callers and actually fixes at least one bug in said callers.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/core/datagram.c |   23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -398,7 +398,7 @@ int skb_copy_datagram_iter(const struct
 			   struct iov_iter *to, int len)
 {
 	int start = skb_headlen(skb);
-	int i, copy = start - offset;
+	int i, copy = start - offset, start_off = offset, n;
 	struct sk_buff *frag_iter;
 
 	trace_skb_copy_datagram_iovec(skb, len);
@@ -407,11 +407,12 @@ int skb_copy_datagram_iter(const struct
 	if (copy > 0) {
 		if (copy > len)
 			copy = len;
-		if (copy_to_iter(skb->data + offset, copy, to) != copy)
+		n = copy_to_iter(skb->data + offset, copy, to);
+		offset += n;
+		if (n != copy)
 			goto short_copy;
 		if ((len -= copy) == 0)
 			return 0;
-		offset += copy;
 	}
 
 	/* Copy paged appendix. Hmm... why does this look so complicated? */
@@ -425,13 +426,14 @@ int skb_copy_datagram_iter(const struct
 		if ((copy = end - offset) > 0) {
 			if (copy > len)
 				copy = len;
-			if (copy_page_to_iter(skb_frag_page(frag),
+			n = copy_page_to_iter(skb_frag_page(frag),
 					      frag->page_offset + offset -
-					      start, copy, to) != copy)
+					      start, copy, to);
+			offset += n;
+			if (n != copy)
 				goto short_copy;
 			if (!(len -= copy))
 				return 0;
-			offset += copy;
 		}
 		start = end;
 	}
@@ -463,6 +465,7 @@ int skb_copy_datagram_iter(const struct
 	 */
 
 fault:
+	iov_iter_revert(to, offset - start_off);
 	return -EFAULT;
 
 short_copy:
@@ -613,7 +616,7 @@ static int skb_copy_and_csum_datagram(co
 				      __wsum *csump)
 {
 	int start = skb_headlen(skb);
-	int i, copy = start - offset;
+	int i, copy = start - offset, start_off = offset;
 	struct sk_buff *frag_iter;
 	int pos = 0;
 	int n;
@@ -623,11 +626,11 @@ static int skb_copy_and_csum_datagram(co
 		if (copy > len)
 			copy = len;
 		n = csum_and_copy_to_iter(skb->data + offset, copy, csump, to);
+		offset += n;
 		if (n != copy)
 			goto fault;
 		if ((len -= copy) == 0)
 			return 0;
-		offset += copy;
 		pos = copy;
 	}
 
@@ -649,12 +652,12 @@ static int skb_copy_and_csum_datagram(co
 						  offset - start, copy,
 						  &csum2, to);
 			kunmap(page);
+			offset += n;
 			if (n != copy)
 				goto fault;
 			*csump = csum_block_add(*csump, csum2, pos);
 			if (!(len -= copy))
 				return 0;
-			offset += copy;
 			pos += copy;
 		}
 		start = end;
@@ -687,6 +690,7 @@ static int skb_copy_and_csum_datagram(co
 		return 0;
 
 fault:
+	iov_iter_revert(to, offset - start_off);
 	return -EFAULT;
 }
 
@@ -771,6 +775,7 @@ int skb_copy_and_csum_datagram_msg(struc
 	}
 	return 0;
 csum_error:
+	iov_iter_revert(&msg->msg_iter, chunk);
 	return -EINVAL;
 fault:
 	return -EFAULT;

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[PATCH 4.10 00/69] 4.10.12-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:40 +0200
  [PATCH 4.10 18/69] CIFS: store results of cifs_reopen_file to avoid infinite wait Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:40 +0200
  [PATCH 4.10 20/69] perf annotate s390: Fix perf annotate error -95 (4.10 regression) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:40 +0200
  [PATCH 4.10 48/69] cpufreq: Bring CPUs up even if cpufreq_online() failed Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:40 +0200
  [PATCH 4.10 35/69] scsi: sr: Sanity check returned mode data Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:40 +0200
  [PATCH 4.10 15/69] drm/etnaviv: fix missing unlock on error in etnaviv_gpu_submit() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:40 +0200
  [PATCH 4.10 08/69] zsmalloc: expand class bit Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:40 +0200
  [PATCH 4.10 11/69] drm/nouveau/mmu/nv4a: use nv04 mmu rather than the nv44 one Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:40 +0200
  [PATCH 4.10 26/69] x86/vdso: Ensure vdso32_enabled gets set to valid values only Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:40 +0200
  [PATCH 4.10 42/69] make skb_copy_datagram_msg() et.al. preserve ->msg_iter on error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:50 +0200
  [PATCH 4.10 67/69] mm: Tighten x86 /dev/mem with zeroing reads Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:50 +0200
  [PATCH 4.10 39/69] target: Avoid mappedlun symlink creation during lun shutdown Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:50 +0200
  [PATCH 4.10 52/69] char: lack of bool string made CONFIG_DEVPORT always on Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:50 +0200
  [PATCH 4.10 34/69] iscsi-target: Drop work-around for legacy GlobalSAN initiator Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:50 +0200
  [PATCH 4.10 43/69] libnvdimm: fix blk free space accounting Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:50 +0200
  [PATCH 4.10 40/69] xen, fbfront: fix connecting to backend Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:50 +0200
  [PATCH 4.10 69/69] virtio-console: avoid DMA from stack Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:50 +0200
  [PATCH 4.10 65/69] ACPI / EC: Use busy polling mode when GPE is not enabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:50 +0200
  [PATCH 4.10 66/69] rtc: tegra: Implement clock handling Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:50 +0200
  [PATCH 4.10 41/69] [iov_iter] new privimitive: iov_iter_revert() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:50 +0200
  [PATCH 4.10 37/69] scsi: qla2xxx: Add fix to read correct register value for ISP82xx. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 16:50 +0200
  [PATCH 4.10 56/69] crypto: algif_aead - Fix bogus request dereference in completion function Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:20 +0200
  [PATCH 4.10 54/69] zram: do not use copy_page with non-page aligned address Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:20 +0200
  [PATCH 4.10 58/69] crypto: ahash - Fix EINPROGRESS notification callback Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:20 +0200
  [PATCH 4.10 61/69] [media] dvb-usb-v2: avoid use-after-free Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:20 +0200
  [PATCH 4.10 36/69] scsi: sd: Consider max_xfer_blocks if opt_xfer_blocks is unusable Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:20 +0200
  [PATCH 4.10 59/69] crypto: lrw - Fix use-after-free on EINPROGRESS Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:20 +0200
  [PATCH 4.10 38/69] scsi: sd: Fix capacity calculation with 32-bit sector_t Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:20 +0200
  [PATCH 4.10 57/69] crypto: xts - Fix use-after-free on EINPROGRESS Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:20 +0200
  [PATCH 4.10 64/69] x86/xen: Fix APIC id mismatch warning on Intel Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:20 +0200
  [PATCH 4.10 62/69] ASoC: Intel: select DW_DMAC_CORE since its mandatory Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:20 +0200
  [PATCH 4.10 55/69] ftrace: Fix function pid filter on instances Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 06/69] thp: fix MADV_DONTNEED vs. MADV_FREE race Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 23/69] x86/signals: Fix lower/upper bound reporting in compat siginfo Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 45/69] libnvdimm: band aid btt vs clear poison locking Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 07/69] thp: fix MADV_DONTNEED vs clear soft dirty race Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 50/69] ftrace: Fix removing of second function probe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 49/69] irqchip/irq-imx-gpcv2: Fix spinlock initialization Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 51/69] drm/i915/gvt: set the correct default value of CTX STATUS PTR Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 46/69] can: ifi: use correct register to read rx status Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 31/69] efi/libstub: Skip GOP with PIXEL_BLT_ONLY format Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 22/69] x86/efi: Dont try to reserve runtime regions Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 25/69] x86, pmem: fix broken __copy_user_nocache cache-bypass assumptions Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 28/69] acpi, nfit, libnvdimm: fix interleave set cookie calculation (64-bit comparison) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 27/69] x86/vdso: Plug race between mapping and ELF header setup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 53/69] Revert "MIPS: Lantiq: Fix cascaded IRQ setup" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 32/69] efi/fb: Avoid reconfiguration of BAR that covers the framebuffer Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 09/69] orangefs: free superblock when mount fails Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 03/69] tcmu: Fix possible overwrite of t_data_sgs last iov[] Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 04/69] tcmu: Fix wrongly calculating of the base_command_size Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 29/69] ACPI / scan: Set the visited flag for all enumerated devices Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 47/69] pwm: rockchip: State of PWM clock should synchronize with PWM enabled state Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 05/69] tcmu: Skip Data-Out blocks before gathering Data-In buffer for BIDI case Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 60/69] parisc: Fix get_user() for 64-bit value on 32-bit kernel Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 44/69] libnvdimm: fix reconfig_mutex, mmap_sem, and jbd2_handle lockdep splat Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:30 +0200
  [PATCH 4.10 19/69] Input: xpad - add support for Razer Wildcat gamepad Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:40 +0200
  [PATCH 4.10 17/69] CIFS: reconnect thread reschedule itself Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:40 +0200
  [PATCH 4.10 13/69] drm/nouveau/kms/nv50: fix double dma_fence_put() when destroying plane state Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:40 +0200
  [PATCH 4.10 02/69] audit: make sure we dont let the retry queue grow without bounds Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:40 +0200
  [PATCH 4.10 01/69] cgroup, kthread: close race window where new kthreads can be migrated to non-root cgroups Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:40 +0200
  [PATCH 4.10 10/69] drm/nouveau/mpeg: mthd returns true on success now Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:40 +0200
  [PATCH 4.10 12/69] drm/nouveau/kms/nv50: fix setting of HeadSetRasterVertBlankDmi method Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 17:40 +0200
  Re: [PATCH 4.10 00/69] 4.10.12-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-04-19 22:40 +0200
    Re: [PATCH 4.10 00/69] 4.10.12-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-20 08:40 +0200
  Re: [PATCH 4.10 00/69] 4.10.12-stable review Guenter Roeck <linux@roeck-us.net> - 2017-04-20 01:30 +0200
    Re: [PATCH 4.10 00/69] 4.10.12-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-20 08:40 +0200

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