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| author | Michael Bommarito <michael.bommarito@gmail.com> | 2026-05-13 12:26:56 -0400 |
|---|---|---|
| committer | Anna Schumaker <anna.schumaker@hammerspace.com> | 2026-06-08 10:21:55 -0400 |
| commit | 2c6bb3c40bc24f6aa8dfbe6fe98c3ad6389203f2 (patch) | |
| tree | 49fb333edb94551ca1fa10d385ebb57875557026 | |
| parent | 37957478be021b92981aa4c99b69f308d3b784d0 (diff) | |
| download | linux-stable-2c6bb3c40bc24f6aa8dfbe6fe98c3ad6389203f2.tar.gz linux-stable-2c6bb3c40bc24f6aa8dfbe6fe98c3ad6389203f2.zip | |
NFSv4/flexfiles: reject zero filehandle version count
ff_layout_alloc_lseg() decodes the filehandle-version array count
from the flexfiles layout body. The value is used as the count for
kzalloc_objs(), and the current code only rejects NULL.
A zero count yields ZERO_SIZE_PTR, which can be stored in
dss_info->fh_versions even though later flexfiles paths assume that at
least one filehandle version exists.
Reject fh_count == 0 before the allocation, matching the existing zero
version_count validation in the flexfiles GETDEVICEINFO parser.
A QEMU/KASAN run with a malformed flexfiles layout hit:
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
RIP: 0010:ff_layout_encode_ff_layoutupdate.isra.0+0x15f/0x750
ff_layout_encode_layoutreturn+0x683/0x970
nfs4_xdr_enc_layoutreturn+0x278/0x3a0
Kernel panic - not syncing: Fatal exception
The patched kernel rejects the malformed layout without KASAN/oops/panic,
and a valid fh_count=1 regression still opens, reads, and unmounts cleanly.
Cc: stable@vger.kernel.org
Fixes: d67ae825a59d ("pnfs/flexfiles: Add the FlexFile Layout Driver")
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Signed-off-by: Anna Schumaker <anna.schumaker@hammerspace.com>
| -rw-r--r-- | fs/nfs/flexfilelayout/flexfilelayout.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c index 6a84d85e0651..99caa8d28c25 100644 --- a/fs/nfs/flexfilelayout/flexfilelayout.c +++ b/fs/nfs/flexfilelayout/flexfilelayout.c @@ -551,6 +551,10 @@ ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh, if (!p) goto out_err_free; fh_count = be32_to_cpup(p); + if (fh_count == 0) { + rc = -EINVAL; + goto out_err_free; + } dss_info->fh_versions = kzalloc_objs(struct nfs_fh, fh_count, gfp_flags); |