linux-stable.git/fs, branch linux-6.18.y

ksmbd: fix out-of-bounds read in smb_check_perm_dacl()

2026-07-04T11:44:21+00:00

commit 1ef06004ed4bd6d3ed8c840d9d1a376b66d4935b upstream.

The permission-check ACE walk in smb_check_perm_dacl() validates the ACE
header size and caps sid.num_subauth at SID_MAX_SUB_AUTHORITIES, but it
never checks that ace->size is actually large enough to contain
num_subauth sub-authorities before compare_sids() dereferences them.

CIFS_SID_BASE_SIZE covers the SID header up to but excluding the
sub_auth[] array, and offsetof(struct smb_ace, sid) is the ACE header,
so the existing guards only guarantee the 8-byte SID base, i.e. zero
sub-authorities. compare_sids() then reads ace->sid.sub_auth[i] for
i < min(local_sid->num_subauth, ace->sid.num_subauth). The local
comparison SIDs (sid_everyone, sid_unix_NFS_mode, and the id_to_sid()
result) always have at least one sub-authority, and an attacker controls
the ACE revision and authority bytes (which lie within the in-bounds SID
base), so they can match one of those SIDs and force the sub_auth read.

A crafted ACE with size == 16 and num_subauth >= 1 placed at the tail of
the security descriptor therefore causes a heap out-of-bounds read of up
to SID_MAX_SUB_AUTHORITIES * sizeof(__le32) bytes past the pntsd
allocation. The security descriptor is loaded by ksmbd_vfs_get_sd_xattr()
into a buffer sized exactly to the on-disk data (kzalloc(sd_size) in
ndr_decode_v4_ntacl()), so the read lands past the allocation. The
malformed descriptor can be stored verbatim via SMB2_SET_INFO (the DACL
is not normalised before being written to the security.NTACL xattr) and
the read fires on a subsequent SMB2_CREATE access check, making this
reachable by an authenticated client on a share that uses ACL xattrs.

Add the missing num_subauth-versus-ace_size check, mirroring the
identical guards already present in the sibling parsers parse_dacl() and
smb_inherit_dacl().

Fixes: d07b26f39246 ("ksmbd: require minimum ACE size in smb_check_perm_dacl()")
Cc: stable@vger.kernel.org
Signed-off-by: Hem Parekh 
Acked-by: Namjae Jeon 
Signed-off-by: Steve French 
Signed-off-by: Greg Kroah-Hartman

NFS: Prevent resource leak in nfs_alloc_server()

2026-07-04T11:44:21+00:00

commit d189f224308c8ac3feeea8e442c99922bd18f1b2 upstream.

It was overlooked to call ida_free() after a failed nfs_alloc_iostats() call.
Thus add the missed function call in an if branch.

Fixes: 1c7251187dc067a6d460cf33ca67da9c1dd87807 ("NFS: add superblock sysfs entries")
Cc: stable@vger.kernel.org
Reported-by: Christophe Jaillet 
Closes: https://lore.kernel.org/linux-nfs/1c8e10c9-def7-4f0d-8aa1-23c8035a38c8@wanadoo.fr/
Signed-off-by: Markus Elfring 
Signed-off-by: Anna Schumaker 
Signed-off-by: Greg Kroah-Hartman

NFSv4: clear exception state on successful mkdir retry

2026-07-04T11:44:21+00:00

commit 238e9b51aa29f48b6243212a3b75c8e48d6b96fd upstream.

After a server returns NFS4ERR_DELAY for an NFSv4 CREATE issued by
mkdir(2), the client correctly waits and retries.  When the retry
succeeds, however, mkdir(2) can still surface -EEXIST to userspace
even though the directory was just created on the server.

Reproducer (random 16-hex names so collisions are not the cause)
against an in-kernel Linux nfsd; reproduces under both NFSv4.0 and
NFSv4.2:

  N=2000000; base=/var/gdc/export
  for ((i=1; i<=N; i++)); do
      d=$base/$(openssl rand -hex 8)
      mkdir "$d" 2>/dev/null || echo "$(date +%T) failed loop=$i $d"
      rmdir "$d" 2>/dev/null
  done

Failures cluster at the cadence at which the server-side auth/export
cache refresh path causes nfsd to return NFS4ERR_DELAY for CREATE.

A wire trace of one failure (the three CREATE RPCs all come from a
single mkdir(2), generated by the do-while in nfs4_proc_mkdir()):

  client -> server  CREATE name=...  -> NFS4ERR_DELAY
  ~100 ms later
  client -> server  CREATE name=...  -> NFS4_OK         (dir created)
  ~80 us later
  client -> server  CREATE name=...  -> NFS4ERR_EXIST   (correct)

Since commit dd862da61e91 ("nfs: fix incorrect handling of large-number
NFS errors in nfs4_do_mkdir()"), nfs4_handle_exception() is called only
when _nfs4_proc_mkdir() returned an error.  That gate breaks retry-state
hygiene: nfs4_do_handle_exception() resets exception.{delay,recovering,
retry} to 0 on entry, so calling it on success is what previously
cleared the retry flag set by the preceding NFS4ERR_DELAY iteration.
With the gate in place, exception.retry stays at 1 after the successful
retry, the loop runs once more, and the resulting CREATE for an
already-created name yields NFS4ERR_EXIST -> -EEXIST to userspace.

Drop the conditional and call nfs4_handle_exception() unconditionally,
matching every other do-while in fs/nfs/nfs4proc.c (nfs4_proc_symlink(),
nfs4_proc_link(), etc.).  The dentry/status separation introduced by
that commit is preserved.

Fixes: dd862da61e91 ("nfs: fix incorrect handling of large-number NFS errors in nfs4_do_mkdir()")
Reported-and-tested-by: Jan Čípa 
Closes: https://lore.kernel.org/linux-nfs/CA+9S74hSp_tJu2Ffe2BPNC2T25gfkhgjjDkdgSsF5c2rnJq_wA@mail.gmail.com/
Reviewed-by: NeilBrown 
Cc: stable@vger.kernel.org
Signed-off-by: Igor Raits 
Signed-off-by: Anna Schumaker 
Signed-off-by: Greg Kroah-Hartman

NFSv4/pNFS: reject zero-length r_addr in nfs4_decode_mp_ds_addr

2026-07-04T11:44:21+00:00

commit 41fe0f7b84f0cb822ae10ab08592996a592b2a25 upstream.

nfs4_decode_mp_ds_addr() decodes the r_netid and r_addr opaques of a
netaddr4 from a GETDEVICEINFO multipath-DS body, then immediately
calls strrchr(buf, '.') to locate the port separator. Both decodes
use xdr_stream_decode_string_dup(), and the current code checks only
"nlen < 0" / "rlen < 0" before dereferencing the returned string.

When the on-wire opaque has length zero, xdr_stream_decode_opaque_inline()
returns 0 and xdr_stream_decode_string_dup() falls through to its
"*str = NULL; return ret" tail, leaving buf NULL with a return value
of 0. The "< 0" check does not catch this, and the next line is
strrchr(NULL, '.'), a kernel NULL pointer dereference reachable from
any pNFS-flexfile client mounted against a malicious or compromised
metadata server.

Reject the zero-length cases explicitly so the decoder fails with
-EBADMSG (treated as a malformed GETDEVICEINFO body) instead of
panicking the client.

Cc: stable@vger.kernel.org
Fixes: 6b7f3cf96364 ("nfs41: pull decode_ds_addr from file layout to generic pnfs")
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Michael Bommarito 
Signed-off-by: Anna Schumaker 
Signed-off-by: Greg Kroah-Hartman

NFSv4/flexfiles: reject zero filehandle version count

2026-07-04T11:44:21+00:00

commit 2c6bb3c40bc24f6aa8dfbe6fe98c3ad6389203f2 upstream.

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 
Signed-off-by: Anna Schumaker 
Signed-off-by: Greg Kroah-Hartman

nfsd: reset write verifier on deferred writeback errors

2026-07-04T11:44:21+00:00

commit 2090b05803faab8a9fa62fbff871007862cac1b7 upstream.

nfsd_vfs_write() and nfsd_commit() both call filemap_check_wb_err() to
detect deferred writeback errors, but neither rotates the server's write
verifier (nn->writeverf) when this check fails. Every other
durable-storage-failure path in these functions calls
commit_reset_write_verifier() before returning an error.

The missing rotation means clients holding UNSTABLE write data under the
current verifier will COMMIT, receive the unchanged verifier back, and
conclude their data is durable — silently dropping data that failed
writeback. This violates the UNSTABLE+COMMIT durability contract
(RFC 1813 §3.3.7, RFC 8881 §18.32).

Add commit_reset_write_verifier() calls at both filemap_check_wb_err()
error sites, matching the pattern used by adjacent error paths in the
same functions. The helper already filters -EAGAIN and -ESTALE
internally, so the calls are unconditionally safe.

Reported-by: Chris Mason 
Fixes: 555dbf1a9aac ("nfsd: Replace use of rwsem with errseq_t")
Cc: stable@vger.kernel.org
Assisted-by: kres:claude-opus-4-6
Signed-off-by: Jeff Layton 
Signed-off-by: Chuck Lever 
Signed-off-by: Greg Kroah-Hartman

nfsd: avoid leaking pre-allocated openowner on unconfirmed retry race

2026-07-04T11:44:21+00:00

commit 57aee7a35bb12753057c5b65d72d1f46c0e95b07 upstream.

When find_or_alloc_open_stateowner() encounters an unconfirmed owner, it
calls release_openowner() and sets oo = NULL. Control then falls through
past the `if (oo)` guard -- which would have freed any pre-allocated
`new` -- and unconditionally executes `new = alloc_stateowner(...)`. If
`new` was already allocated on a prior iteration, the pointer is
silently overwritten and the previous allocation (slab object + owner
name buffer) is leaked.

This requires a race: two NFSv4.0 OPEN threads with the same owner
string, where a concurrent thread inserts a new unconfirmed owner into
the hash between retry iterations. The window is narrow but repeatable
under adversarial conditions.

Fix by adding `goto retry` after `oo = NULL` so the already-allocated
`new` is reused on the next iteration rather than overwritten.

Reported-by: Chris Mason 
Fixes: 23df17788c62 ("nfsd: perform all find_openstateowner_str calls in the one place.")
Cc: stable@vger.kernel.org
Assisted-by: kres:claude-opus-4-6
Signed-off-by: Jeff Layton 
Signed-off-by: Chuck Lever 
Signed-off-by: Greg Kroah-Hartman

nfsd: check get_user() return when reading princhashlen

2026-07-04T11:44:21+00:00

commit e186fa1c057f5eccb22afb1e83e34c0627085868 upstream.

In __cld_pipe_inprogress_downcall(), the get_user() that reads
princhashlen from the userspace cld_msg_v2 buffer does not check its
return value. A failing copy leaves princhashlen with uninitialised
stack contents, which are then used to drive memdup_user() and stored
as princhash.len on the resulting reclaim record. The other get_user()
calls in this function all check the return; only this one is missed,
which is most likely a copy-paste oversight from when v2 upcalls were
introduced.

Mirror the existing pattern used a few lines above for namelen.
namecopy is declared with __free(kfree) so the early return cleans up
the already-allocated buffer automatically.

Fixes: 6ee95d1c8991 ("nfsd: add support for upcall version 2")
Cc: stable@vger.kernel.org
Signed-off-by: Dominik Woźniak 
Reviewed-by: Jeff Layton 
Signed-off-by: Chuck Lever 
Signed-off-by: Greg Kroah-Hartman

nfsd: fix inverted cp_ttl check in async copy reaper

2026-07-04T11:44:21+00:00

commit 0150459b05490b88b7e7378a31550a9e07b5517c upstream.

nfsd4_async_copy_reaper() is supposed to keep completed async copy
state around for NFSD_COPY_INITIAL_TTL (10) laundromat ticks so
that OFFLOAD_STATUS can report the result, then reap the state once
the countdown expires.

The TTL predicate is inverted: `if (--copy->cp_ttl)` is true while
ticks remain and false when the counter reaches zero.  This causes
the copy to be reaped on the very first tick (cp_ttl goes from 10
to 9, which is non-zero) instead of after all 10 ticks elapse.
Once reaped, OFFLOAD_STATUS returns NFS4ERR_BAD_STATEID because
the copy state has already been freed.

Fix by negating the test so that cleanup runs when the TTL expires.

Fixes: aa0ebd21df9c ("NFSD: Add nfsd4_copy time-to-live")
Cc: stable@vger.kernel.org
Reported-by: Chris Mason 
Assisted-by: kres:claude-opus-4-6
Signed-off-by: Jeff Layton 
Signed-off-by: Chuck Lever 
Signed-off-by: Greg Kroah-Hartman

nfsd: fix posix_acl leak on SETACL decode failure

2026-07-04T11:44:21+00:00

commit 0853ac544c590880d797b04daa33fcb72b6be0e1 upstream.

nfsaclsvc_decode_setaclargs() and nfs3svc_decode_setaclargs() each
call nfs_stream_decode_acl() twice, first for NFS_ACL and then for
NFS_DFACL.  Each successful call transfers ownership of a freshly
allocated posix_acl into argp->acl_access or argp->acl_default.  If
the first call succeeds but the second fails, the decoder returns
false and argp->acl_access is left dangling.

ACLPROC2_SETACL.pc_release was wired to nfssvc_release_attrstat and
ACLPROC3_SETACL.pc_release was wired to nfs3svc_release_fhandle.
Both only call fh_put() and have no knowledge of the ACL fields on
argp.  The posix_acl_release() pairs sat at the out: labels inside
nfsacld_proc_setacl() and nfsd3_proc_setacl(), but svc_process()
skips pc_func when pc_decode returns false, so that cleanup is
unreachable on decode failure:

    svc_process_common()
      pc_decode()                  /* decode_setaclargs: false */
      /* pc_func skipped */
      pc_release()                 /* fh_put only -- ACLs leaked */

The orphaned posix_acl is leaked for the lifetime of the server.

Fix by adding nfsaclsvc_release_setacl() and nfs3svc_release_setacl(),
which release both argp->acl_access and argp->acl_default in addition
to fh_put(), and wiring them as pc_release for their respective SETACL
procedures.  pc_release runs on every path svc_process() takes after
decode, including decode failure, so the posix_acl_release() pairs are
removed from the proc functions' out: labels to keep ownership in one
place.  This matches the existing release_getacl() pattern used by
the sibling GETACL procedures.

Fixes: a257cdd0e217 ("[PATCH] NFSD: Add server support for NFSv3 ACLs.")
Cc: stable@vger.kernel.org
Assisted-by: kres:claude-opus-4-7
Signed-off-by: Jeff Layton 
Signed-off-by: Chuck Lever 
Signed-off-by: Greg Kroah-Hartman