kernel/linux.git/fs/nfsd, branch v5.10.257

nfsd: fix heap overflow in NFSv4.0 LOCK replay cache

2026-04-18T08:31:00+00:00

[ Upstream commit 5133b61aaf437e5f25b1b396b14242a6bb0508e2 ] The NFSv4.0 replay cache uses a fixed 112-byte inline buffer (rp_ibuf[NFSD4_REPLAY_ISIZE]) to store encoded operation responses. This size was calculated based on OPEN responses and does not account for LOCK denied responses, which include the conflicting lock owner as a variable-length field up to 1024 bytes (NFS4_OPAQUE_LIMIT). When a LOCK operation is denied due to a conflict with an existing lock that has a large owner, nfsd4_encode_operation() copies the full encoded response into the undersized replay buffer via read_bytes_from_xdr_buf() with no bounds check. This results in a slab-out-of-bounds write of up to 944 bytes past the end of the buffer, corrupting adjacent heap memory. This can be triggered remotely by an unauthenticated attacker with two cooperating NFSv4.0 clients: one sets a lock with a large owner string, then the other requests a conflicting lock to provoke the denial. We could fix this by increasing NFSD4_REPLAY_ISIZE to allow for a full opaque, but that would increase the size of every stateowner, when most lockowners are not that large. Instead, fix this by checking the encoded response length against NFSD4_REPLAY_ISIZE before copying into the replay buffer. If the response is too large, set rp_buflen to 0 to skip caching the replay payload. The status is still cached, and the client already received the correct response on the original request. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@kernel.org Reported-by: Nicholas Carlini Tested-by: Nicholas Carlini Signed-off-by: Jeff Layton Signed-off-by: Chuck Lever [ replaced `op_status_offset + XDR_UNIT` with existing `post_err_offset` variable ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

NFSD: Hold net reference for the lifetime of /proc/fs/nfs/exports fd

2026-04-18T08:31:00+00:00

[ Upstream commit e7fcf179b82d3a3730fd8615da01b087cc654d0b ] The /proc/fs/nfs/exports proc entry is created at module init and persists for the module's lifetime. exports_proc_open() captures the caller's current network namespace and stores its svc_export_cache in seq->private, but takes no reference on the namespace. If the namespace is subsequently torn down (e.g. container destruction after the opener does setns() to a different namespace), nfsd_net_exit() calls nfsd_export_shutdown() which frees the cache. Subsequent reads on the still-open fd dereference the freed cache_detail, walking a freed hash table. Hold a reference on the struct net for the lifetime of the open file descriptor. This prevents nfsd_net_exit() from running -- and thus prevents nfsd_export_shutdown() from freeing the cache -- while any exports fd is open. cache_detail already stores its net pointer (cd->net, set by cache_create_net()), so exports_release() can retrieve it without additional per-file storage. Reported-by: Misbah Anjum N Closes: https://lore.kernel.org/linux-nfs/dcd371d3a95815a84ba7de52cef447b8@linux.ibm.com/ Fixes: 96d851c4d28d ("nfsd: use proper net while reading "exports" file") Cc: stable@vger.kernel.org Reviewed-by: Jeff Layton Reviewed-by: NeilBrown Tested-by: Olga Kornievskaia Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

nfsd: define exports_proc_ops with CONFIG_PROC_FS

2026-04-18T08:31:00+00:00

[ Upstream commit 340086da9a87820b40601141a0e9e87c954ac006 ] gcc with W=1 and ! CONFIG_PROC_FS fs/nfsd/nfsctl.c:161:30: error: ‘exports_proc_ops’ defined but not used [-Werror=unused-const-variable=] 161 | static const struct proc_ops exports_proc_ops = { | ^~~~~~~~~~~~~~~~ The only use of exports_proc_ops is when CONFIG_PROC_FS is defined, so its definition should be likewise conditional. Signed-off-by: Tom Rix Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Stable-dep-of: e7fcf179b82d ("NFSD: Hold net reference for the lifetime of /proc/fs/nfs/exports fd") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

nfsd: fix return error code for nfsd_map_name_to_[ug]id

2026-03-04T12:20:19+00:00

[ Upstream commit 404d779466646bf1461f2090ff137e99acaecf42 ] idmap lookups can time out while the cache is waiting for a userspace upcall reply. In that case cache_check() returns -ETIMEDOUT to callers. The nfsd_map_name_to_[ug]id functions currently proceed with attempting to map the id to a kuid despite a potentially temporary failure to perform the idmap lookup. This results in the code returning the error NFSERR_BADOWNER which can cause client operations to return to userspace with failure. Fix this by returning the failure status before attempting kuid mapping. This will return NFSERR_JUKEBOX on idmap lookup timeout so that clients can retry the operation instead of aborting it. Fixes: 65e10f6d0ab0 ("nfsd: Convert idmap to use kuids and kgids") Cc: stable@vger.kernel.org Signed-off-by: Anthony Iliopoulos Reviewed-by: NeilBrown Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

nfsd: never defer requests during idmap lookup

2026-03-04T12:19:34+00:00

[ Upstream commit f9c206cdc4266caad6a9a7f46341420a10f03ccb ] During v4 request compound arg decoding, some ops (e.g. SETATTR) can trigger idmap lookup upcalls. When those upcall responses get delayed beyond the allowed time limit, cache_check() will mark the request for deferral and cause it to be dropped. This prevents nfs4svc_encode_compoundres from being executed, and thus the session slot flag NFSD4_SLOT_INUSE never gets cleared. Subsequent client requests will fail with NFSERR_JUKEBOX, given that the slot will be marked as in-use, making the SEQUENCE op fail. Fix this by making sure that the RQ_USEDEFERRAL flag is always clear during nfs4svc_decode_compoundargs(), since no v4 request should ever be deferred. Fixes: 2f425878b6a7 ("nfsd: don't use the deferral service, return NFS4ERR_DELAY") Signed-off-by: Anthony Iliopoulos Reviewed-by: NeilBrown Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

nfsd: provide locking for v4_end_grace

2026-01-19T12:12:11+00:00

[ Upstream commit 2857bd59feb63fcf40fe4baf55401baea6b4feb4 ] Writing to v4_end_grace can race with server shutdown and result in memory being accessed after it was freed - reclaim_str_hashtbl in particularly. We cannot hold nfsd_mutex across the nfsd4_end_grace() call as that is held while client_tracking_op->init() is called and that can wait for an upcall to nfsdcltrack which can write to v4_end_grace, resulting in a deadlock. nfsd4_end_grace() is also called by the landromat work queue and this doesn't require locking as server shutdown will stop the work and wait for it before freeing anything that nfsd4_end_grace() might access. However, we must be sure that writing to v4_end_grace doesn't restart the work item after shutdown has already waited for it. For this we add a new flag protected with nn->client_lock. It is set only while it is safe to make client tracking calls, and v4_end_grace only schedules work while the flag is set with the spinlock held. So this patch adds a nfsd_net field "client_tracking_active" which is set as described. Another field "grace_end_forced", is set when v4_end_grace is written. After this is set, and providing client_tracking_active is set, the laundromat is scheduled. This "grace_end_forced" field bypasses other checks for whether the grace period has finished. This resolves a race which can result in use-after-free. Reported-by: Li Lingfeng Closes: https://lore.kernel.org/linux-nfs/20250623030015.2353515-1-neil@brown.name/T/#t Fixes: 7f5ef2e900d9 ("nfsd: add a v4_end_grace file to /proc/fs/nfsd") Cc: stable@vger.kernel.org Signed-off-by: NeilBrown Tested-by: Li Lingfeng Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever [ Adjust context ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

NFSD: NFSv4 file creation neglects setting ACL

2026-01-19T12:12:06+00:00

[ Upstream commit 913f7cf77bf14c13cfea70e89bcb6d0b22239562 ] An NFSv4 client that sets an ACL with a named principal during file creation retrieves the ACL afterwards, and finds that it is only a default ACL (based on the mode bits) and not the ACL that was requested during file creation. This violates RFC 8881 section 6.4.1.3: "the ACL attribute is set as given". The issue occurs in nfsd_create_setattr(). On 6.1.y, the check to determine whether nfsd_setattr() should be called is simply "iap->ia_valid", which only accounts for iattr changes. When only an ACL is present (and no iattr fields are set), nfsd_setattr() is skipped and the POSIX ACL is never applied to the inode. Subsequently, when the client retrieves the ACL, the server finds no POSIX ACL on the inode and returns one generated from the file's mode bits rather than returning the originally-specified ACL. Reported-by: Aurelien Couderc Fixes: c0cbe70742f4 ("NFSD: add posix ACLs to struct nfsd_attrs") Cc: stable@vger.kernel.org [ cel: Adjust nfsd_create_setattr() instead of nfsd_attrs_valid() ] Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman

NFSD: Clear SECLABEL in the suppattr_exclcreat bitmap

2026-01-19T12:12:03+00:00

[ Upstream commit 27d17641cacfedd816789b75d342430f6b912bd2 ] >>From RFC 8881: 5.8.1.14. Attribute 75: suppattr_exclcreat > The bit vector that would set all REQUIRED and RECOMMENDED > attributes that are supported by the EXCLUSIVE4_1 method of file > creation via the OPEN operation. The scope of this attribute > applies to all objects with a matching fsid. There's nothing in RFC 8881 that states that suppattr_exclcreat is or is not allowed to contain bits for attributes that are clear in the reported supported_attrs bitmask. But it doesn't make sense for an NFS server to indicate that it /doesn't/ implement an attribute, but then also indicate that clients /are/ allowed to set that attribute using OPEN(create) with EXCLUSIVE4_1. Ensure that the SECURITY_LABEL and ACL bits are not set in the suppattr_exclcreat bitmask when they are also not set in the supported_attrs bitmask. Fixes: 8c18f2052e75 ("nfsd41: SUPPATTR_EXCLCREAT attribute") Cc: stable@vger.kernel.org Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever [ Adjust context ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

nfsd: Drop the client reference in client_states_open()

2026-01-19T12:11:59+00:00

commit 1f941b2c23fd34c6f3b76d36f9d0a2528fa92b8f upstream. In error path, call drop_client() to drop the reference obtained by get_nfsdfs_clp(). Fixes: 78599c42ae3c ("nfsd4: add file to display list of client's opens") Cc: stable@vger.kernel.org Reviewed-by: Jeff Layton Signed-off-by: Haoxiang Li Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman

nfsd: Mark variable __maybe_unused to avoid W=1 build break

2026-01-19T12:11:51+00:00

commit ebae102897e760e9e6bc625f701dd666b2163bd1 upstream. Clang is not happy about set but (in some cases) unused variable: fs/nfsd/export.c:1027:17: error: variable 'inode' set but not used [-Werror,-Wunused-but-set-variable] since it's used as a parameter to dprintk() which might be configured a no-op. To avoid uglifying code with the specific ifdeffery just mark the variable __maybe_unused. The commit [1], which introduced this behaviour, is quite old and hence the Fixes tag points to the first of the Git era. Link: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=0431923fb7a1 [1] Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Andy Shevchenko Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman