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FAILED: patch "[PATCH] xfs: fix out of bounds memory read error in symlink repair" failed to apply to 6.12-stable tree

PATCH In review [email protected] 3 participants 4 messages Nov 24, 2025 – Nov 26, 2025

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#0 lore raw

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 678e1cc2f482e0985a0613ab4a5bf89c497e5acc
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025112403-evaluate-bogged-d093@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 678e1cc2f482e0985a0613ab4a5bf89c497e5acc Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <[email protected]>
Date: Wed, 12 Nov 2025 08:35:18 -0800
Subject: [PATCH] xfs: fix out of bounds memory read error in symlink repair

xfs/286 produced this report on my test fleet:

==================================================================

 BUG: KFENCE: out-of-bounds read in memcpy_orig+0x54/0x110

Out-of-bounds read at 0xffff88843fe9e038 (184B right of kfence-#184):

  memcpy_orig+0x54/0x110
  xrep_symlink_salvage_inline+0xb3/0xf0 [xfs]
  xrep_symlink_salvage+0x100/0x110 [xfs]
  xrep_symlink+0x2e/0x80 [xfs]
  xrep_attempt+0x61/0x1f0 [xfs]
  xfs_scrub_metadata+0x34f/0x5c0 [xfs]
  xfs_ioc_scrubv_metadata+0x387/0x560 [xfs]
  xfs_file_ioctl+0xe23/0x10e0 [xfs]
  __x64_sys_ioctl+0x76/0xc0
  do_syscall_64+0x4e/0x1e0
  entry_SYSCALL_64_after_hwframe+0x4b/0x53

kfence-#184: 0xffff88843fe9df80-0xffff88843fe9dfea, size=107, cache=kmalloc-128

allocated by task 3470 on cpu 1 at 263329.131592s (192823.508886s ago):

  xfs_init_local_fork+0x79/0xe0 [xfs]
  xfs_iformat_local+0xa4/0x170 [xfs]
  xfs_iformat_data_fork+0x148/0x180 [xfs]
  xfs_inode_from_disk+0x2cd/0x480 [xfs]
  xfs_iget+0x450/0xd60 [xfs]
  xfs_bulkstat_one_int+0x6b/0x510 [xfs]
  xfs_bulkstat_iwalk+0x1e/0x30 [xfs]
  xfs_iwalk_ag_recs+0xdf/0x150 [xfs]
  xfs_iwalk_run_callbacks+0xb9/0x190 [xfs]
  xfs_iwalk_ag+0x1dc/0x2f0 [xfs]
  xfs_iwalk_args.constprop.0+0x6a/0x120 [xfs]
  xfs_iwalk+0xa4/0xd0 [xfs]
  xfs_bulkstat+0xfa/0x170 [xfs]
  xfs_ioc_fsbulkstat.isra.0+0x13a/0x230 [xfs]
  xfs_file_ioctl+0xbf2/0x10e0 [xfs]
  __x64_sys_ioctl+0x76/0xc0
  do_syscall_64+0x4e/0x1e0
  entry_SYSCALL_64_after_hwframe+0x4b/0x53

 CPU: 1 UID: 0 PID: 1300113 Comm: xfs_scrub Not tainted 6.18.0-rc4-djwx #rc4 PREEMPT(lazy)  3d744dd94e92690f00a04398d2bd8631dcef1954
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-4.module+el8.8.0+21164+ed375313 04/01/2014
 ==================================================================

On further analysis, I realized that the second parameter to min() is not correct. xfs_ifork::if_bytes is the size of the xfs_ifork::if_data buffer. if_bytes can be smaller than the data fork size because:

(a) the forkoff code tries to keep the data area as large as possible
(b) for symbolic links, if_bytes is the ondisk file size + 1
(c) forkoff is always a multiple of 8.

Case in point: for a single-byte symlink target, forkoff will be 8 but the buffer will only be 2 bytes long.

In other words, the logic here is wrong and we walk off the end of the incore buffer. Fix that.

Cc [email protected] # v6.10
Fixes 2651923d8d8db0 ("xfs: online repair of symbolic links")
Signed-off-by Darrick J. Wong <[email protected]>
Reviewed-by Christoph Hellwig <[email protected]>
Signed-off-by Carlos Maiolino <[email protected]>
fs/xfs/scrub/symlink_repair.c +1 -1
index 5902398185a8..df629892462f 100644
@@ -184,7 +184,7 @@ xrep_symlink_salvage_inline(
 	    sc->ip->i_disk_size == 1 && old_target[0] == '?')
 		return 0;
 
-	nr = min(XFS_SYMLINK_MAXLEN, xfs_inode_data_fork_size(ip));
+	nr = min(XFS_SYMLINK_MAXLEN, ifp->if_bytes);
 	memcpy(target_buf, ifp->if_data, nr);
 	return nr;
 }
maintainer
#1 lore raw

PATCH 1/2 xfs: Replace strncpy with memcpy

From: Marcelo Moreira <[email protected]>

[ Upstream commit 33ddc796ecbd50cd6211aa9e9eddbf4567038b49 ]

The changes modernizes the code by aligning it with current kernel best practices. It improves code clarity and consistency, as strncpy is deprecated as explained in Documentation/process/deprecated.rst. This change does not alter the functionality or introduce any behavioral changes.

Suggested-by Dave Chinner <[email protected]>
Reviewed-by Christoph Hellwig <[email protected]>
Reviewed-by Carlos Maiolino <[email protected]>
Signed-off-by Marcelo Moreira <[email protected]>
Reviewed-by Darrick J. Wong <[email protected]>
Signed-off-by Carlos Maiolino <[email protected]>

Stable-dep-of: 678e1cc2f482 ("xfs: fix out of bounds memory read error in symlink repair")

Signed-off-by Sasha Levin <[email protected]>
---
 fs/xfs/scrub/symlink_repair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
fs/xfs/scrub/symlink_repair.c +1 -1
index 953ce7be78dc2..5902398185a89 100644
@@ -185,7 +185,7 @@ xrep_symlink_salvage_inline(
 		return 0;
 
 	nr = min(XFS_SYMLINK_MAXLEN, xfs_inode_data_fork_size(ip));
-	strncpy(target_buf, ifp->if_data, nr);
+	memcpy(target_buf, ifp->if_data, nr);
 	return nr;
 }
Signature · 1 line
2.51.0
maintainer
#2 lore raw

PATCH 2/2 xfs: fix out of bounds memory read error in symlink repair

From: "Darrick J. Wong" <[email protected]>

[ Upstream commit 678e1cc2f482e0985a0613ab4a5bf89c497e5acc ]

xfs/286 produced this report on my test fleet:

==================================================================

 BUG: KFENCE: out-of-bounds read in memcpy_orig+0x54/0x110

Out-of-bounds read at 0xffff88843fe9e038 (184B right of kfence-#184):

  memcpy_orig+0x54/0x110
  xrep_symlink_salvage_inline+0xb3/0xf0 [xfs]
  xrep_symlink_salvage+0x100/0x110 [xfs]
  xrep_symlink+0x2e/0x80 [xfs]
  xrep_attempt+0x61/0x1f0 [xfs]
  xfs_scrub_metadata+0x34f/0x5c0 [xfs]
  xfs_ioc_scrubv_metadata+0x387/0x560 [xfs]
  xfs_file_ioctl+0xe23/0x10e0 [xfs]
  __x64_sys_ioctl+0x76/0xc0
  do_syscall_64+0x4e/0x1e0
  entry_SYSCALL_64_after_hwframe+0x4b/0x53

kfence-#184: 0xffff88843fe9df80-0xffff88843fe9dfea, size=107, cache=kmalloc-128

allocated by task 3470 on cpu 1 at 263329.131592s (192823.508886s ago):

  xfs_init_local_fork+0x79/0xe0 [xfs]
  xfs_iformat_local+0xa4/0x170 [xfs]
  xfs_iformat_data_fork+0x148/0x180 [xfs]
  xfs_inode_from_disk+0x2cd/0x480 [xfs]
  xfs_iget+0x450/0xd60 [xfs]
  xfs_bulkstat_one_int+0x6b/0x510 [xfs]
  xfs_bulkstat_iwalk+0x1e/0x30 [xfs]
  xfs_iwalk_ag_recs+0xdf/0x150 [xfs]
  xfs_iwalk_run_callbacks+0xb9/0x190 [xfs]
  xfs_iwalk_ag+0x1dc/0x2f0 [xfs]
  xfs_iwalk_args.constprop.0+0x6a/0x120 [xfs]
  xfs_iwalk+0xa4/0xd0 [xfs]
  xfs_bulkstat+0xfa/0x170 [xfs]
  xfs_ioc_fsbulkstat.isra.0+0x13a/0x230 [xfs]
  xfs_file_ioctl+0xbf2/0x10e0 [xfs]
  __x64_sys_ioctl+0x76/0xc0
  do_syscall_64+0x4e/0x1e0
  entry_SYSCALL_64_after_hwframe+0x4b/0x53

 CPU: 1 UID: 0 PID: 1300113 Comm: xfs_scrub Not tainted 6.18.0-rc4-djwx #rc4 PREEMPT(lazy)  3d744dd94e92690f00a04398d2bd8631dcef1954
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-4.module+el8.8.0+21164+ed375313 04/01/2014
 ==================================================================

On further analysis, I realized that the second parameter to min() is not correct. xfs_ifork::if_bytes is the size of the xfs_ifork::if_data buffer. if_bytes can be smaller than the data fork size because:

(a) the forkoff code tries to keep the data area as large as possible
(b) for symbolic links, if_bytes is the ondisk file size + 1
(c) forkoff is always a multiple of 8.

Case in point: for a single-byte symlink target, forkoff will be 8 but the buffer will only be 2 bytes long.

In other words, the logic here is wrong and we walk off the end of the incore buffer. Fix that.

Cc [email protected] # v6.10
Fixes 2651923d8d8db0 ("xfs: online repair of symbolic links")
Signed-off-by Darrick J. Wong <[email protected]>
Reviewed-by Christoph Hellwig <[email protected]>
Signed-off-by Carlos Maiolino <[email protected]>
Signed-off-by Sasha Levin <[email protected]>
---
 fs/xfs/scrub/symlink_repair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
fs/xfs/scrub/symlink_repair.c +1 -1
index 5902398185a89..df629892462fe 100644
@@ -184,7 +184,7 @@ xrep_symlink_salvage_inline(
 	    sc->ip->i_disk_size == 1 && old_target[0] == '?')
 		return 0;
 
-	nr = min(XFS_SYMLINK_MAXLEN, xfs_inode_data_fork_size(ip));
+	nr = min(XFS_SYMLINK_MAXLEN, ifp->if_bytes);
 	memcpy(target_buf, ifp->if_data, nr);
 	return nr;
 }
Signature · 1 line
2.51.0
Acked-by on v1 1/2
#3 lore raw

Re: [PATCH 6.12.y 1/2] xfs: Replace strncpy with memcpy

In reply to Sasha Levin
Quoted 9 lines · Sasha Levin

From: Marcelo Moreira <[email protected]>

[ Upstream commit 33ddc796ecbd50cd6211aa9e9eddbf4567038b49 ]

The changes modernizes the code by aligning it with current kernel best practices. It improves code clarity and consistency, as strncpy is deprecated as explained in Documentation/process/deprecated.rst. This change does not alter the functionality or introduce any behavioral changes.

Quoted 8 lines
Suggested-by Dave Chinner <[email protected]>
Reviewed-by Christoph Hellwig <[email protected]>
Reviewed-by Carlos Maiolino <[email protected]>
Signed-off-by Marcelo Moreira <[email protected]>
Reviewed-by Darrick J. Wong <[email protected]>
Signed-off-by Carlos Maiolino <[email protected]>

Stable-dep-of: 678e1cc2f482 ("xfs: fix out of bounds memory read error in symlink repair")

Signed-off-by Sasha Levin <[email protected]>

Both of these backports also look good to me,

Acked-by "Darrick J. Wong" <[email protected]>

--D

Quoted 20 lines
---
 fs/xfs/scrub/symlink_repair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
fs/xfs/scrub/symlink_repair.c +1 -1
index 953ce7be78dc2..5902398185a89 100644
@@ -185,7 +185,7 @@ xrep_symlink_salvage_inline(
 		return 0;
 
 	nr = min(XFS_SYMLINK_MAXLEN, xfs_inode_data_fork_size(ip));
-	strncpy(target_buf, ifp->if_data, nr);
+	memcpy(target_buf, ifp->if_data, nr);
 	return nr;
 }
Signature · 1 line
2.51.0