The patch below does not apply to the 6.17-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 stable@vger.kernel.org.

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-6.17.y git checkout FETCH_HEAD git cherry-pick -x 678e1cc2f482e0985a0613ab4a5bf89c497e5acc # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025112457-shining-trough-db05@gregkh' --subject-prefix 'PATCH 6.17.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" djwong@kernel.org 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: stable@vger.kernel.org # v6.10 Fixes: 2651923d8d8db0 ("xfs: online repair of symbolic links") Signed-off-by: Darrick J. Wong djwong@kernel.org Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Carlos Maiolino cem@kernel.org

diff --git a/fs/xfs/scrub/symlink_repair.c b/fs/xfs/scrub/symlink_repair.c index 5902398185a8..df629892462f 100644 --- a/fs/xfs/scrub/symlink_repair.c +++ b/fs/xfs/scrub/symlink_repair.c @@ -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; }