kernel/linux.git/fs/nfsd, branch v6.18.21

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

2026-03-25T10:10:30+00:00

commit 5133b61aaf437e5f25b1b396b14242a6bb0508e2 upstream. 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 Signed-off-by: Greg Kroah-Hartman

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

2026-03-25T10:10:30+00:00

commit e7fcf179b82d3a3730fd8615da01b087cc654d0b upstream. 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: Greg Kroah-Hartman

NFSD: Defer sub-object cleanup in export put callbacks

2026-03-25T10:10:30+00:00

commit 48db892356d6cb80f6942885545de4a6dd8d2a29 upstream. svc_export_put() calls path_put() and auth_domain_put() immediately when the last reference drops, before the RCU grace period. RCU readers in e_show() and c_show() access both ex_path (via seq_path/d_path) and ex_client->name (via seq_escape) without holding a reference. If cache_clean removes the entry and drops the last reference concurrently, the sub-objects are freed while still in use, producing a NULL pointer dereference in d_path. Commit 2530766492ec ("nfsd: fix UAF when access ex_uuid or ex_stats") moved kfree of ex_uuid and ex_stats into the call_rcu callback, but left path_put() and auth_domain_put() running before the grace period because both may sleep and call_rcu callbacks execute in softirq context. Replace call_rcu/kfree_rcu with queue_rcu_work(), which defers the callback until after the RCU grace period and executes it in process context where sleeping is permitted. This allows path_put() and auth_domain_put() to be moved into the deferred callback alongside the other resource releases. Apply the same fix to expkey_put(), which has the identical pattern with ek_path and ek_client. A dedicated workqueue scopes the shutdown drain to only NFSD export release work items; flushing the shared system_unbound_wq would stall on unrelated work from other subsystems. nfsd_export_shutdown() uses rcu_barrier() followed by flush_workqueue() to ensure all deferred release callbacks complete before the export caches are destroyed. Reported-by: Misbah Anjum N Closes: https://lore.kernel.org/linux-nfs/dcd371d3a95815a84ba7de52cef447b8@linux.ibm.com/ Fixes: c224edca7af0 ("nfsd: no need get cache ref when protected by rcu") Fixes: 1b10f0b603c0 ("SUNRPC: no need get cache ref when protected by rcu") Cc: stable@vger.kernel.org Reviwed-by: Jeff Layton Reviewed-by: NeilBrown Tested-by: Olga Kornievskaia Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman

nfsd: Fix cred ref leak in nfsd_nl_listener_set_doit().

2026-03-19T15:08:34+00:00

commit 92978c83bb4eef55d02a6c990c01c423131eefa7 upstream. nfsd_nl_listener_set_doit() uses get_current_cred() without put_cred(). As we can see from other callers, svc_xprt_create_from_sa() does not require the extra refcount. nfsd_nl_listener_set_doit() is always in the process context, sendmsg(), and current->cred does not go away. Let's use current_cred() in nfsd_nl_listener_set_doit(). Fixes: 16a471177496 ("NFSD: add listener-{set,get} netlink command") Cc: stable@vger.kernel.org Signed-off-by: Kuniyuki Iwashima Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman

nfsd: Fix cred ref leak in nfsd_nl_threads_set_doit().

2026-03-12T11:09:41+00:00

commit 1cb968a2013ffa8112d52ebe605009ea1c6a582c upstream. syzbot reported memory leak of struct cred. [0] nfsd_nl_threads_set_doit() passes get_current_cred() to nfsd_svc(), but put_cred() is not called after that. The cred is finally passed down to _svc_xprt_create(), which calls get_cred() with the cred for struct svc_xprt. The ownership of the refcount by get_current_cred() is not transferred to anywhere and is just leaked. nfsd_svc() is also called from write_threads(), but it does not bump file->f_cred there. nfsd_nl_threads_set_doit() is called from sendmsg() and current->cred does not go away. Let's use current_cred() in nfsd_nl_threads_set_doit(). [0]: BUG: memory leak unreferenced object 0xffff888108b89480 (size 184): comm "syz-executor", pid 5994, jiffies 4294943386 hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace (crc 369454a7): kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline] slab_post_alloc_hook mm/slub.c:4958 [inline] slab_alloc_node mm/slub.c:5263 [inline] kmem_cache_alloc_noprof+0x412/0x580 mm/slub.c:5270 prepare_creds+0x22/0x600 kernel/cred.c:185 copy_creds+0x44/0x290 kernel/cred.c:286 copy_process+0x7a7/0x2870 kernel/fork.c:2086 kernel_clone+0xac/0x6e0 kernel/fork.c:2651 __do_sys_clone+0x7f/0xb0 kernel/fork.c:2792 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fixes: 924f4fb003ba ("NFSD: convert write_threads to netlink command") Cc: stable@vger.kernel.org Reported-by: syzbot+dd3b43aa0204089217ee@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/69744674.a00a0220.33ccc7.0000.GAE@google.com/ Tested-by: syzbot+dd3b43aa0204089217ee@syzkaller.appspotmail.com Signed-off-by: Kuniyuki Iwashima Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman

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

2026-03-04T12:21:17+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: fix setting FMODE_NOCMTIME in nfs4_open_delegation

2026-03-04T12:21:17+00:00

[ Upstream commit 41b0a87bc60d5ccfa8575481ddb4d4d8758507fa ] fstests generic/215 and generic/407 were failing because the server wasn't updating mtime properly. When deleg attribute support is not compiled in and thus no attribute delegation was given, the server was skipping updating mtime and ctime because FMODE_NOCMTIME was uncoditionally set for the write delegation. Fixes: e5e9b24ab8fa ("nfsd: freeze c/mtime updates with outstanding WRITE_ATTRS delegation") Cc: stable@vger.kernel.org Signed-off-by: Olga Kornievskaia Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

nfsd: never defer requests during idmap lookup

2026-02-26T22:59:18+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

NFS: NFSERR_INVAL is not defined by NFSv2

2026-02-26T22:59:18+00:00

[ Upstream commit 0ac903d1bfdce8ff40657c2b7d996947b72b6645 ] A documenting comment in include/uapi/linux/nfs.h claims incorrectly that NFSv2 defines NFSERR_INVAL. There is no such definition in either RFC 1094 or https://pubs.opengroup.org/onlinepubs/9629799/chap7.htm NFS3ERR_INVAL is introduced in RFC 1813. NFSD returns NFSERR_INVAL for PROC_GETACL, which has no specification (yet). However, nfsd_map_status() maps nfserr_symlink and nfserr_wrong_type to nfserr_inval, which does not align with RFC 1094. This logic was introduced only recently by commit 438f81e0e92a ("nfsd: move error choice for incorrect object types to version-specific code."). Given that we have no INVAL or SERVERFAULT status in NFSv2, probably the only choice is NFSERR_IO. Fixes: 438f81e0e92a ("nfsd: move error choice for incorrect object types to version-specific code.") Reviewed-by: NeilBrown Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

NFSD: Remove NFSERR_EAGAIN

2026-01-17T15:35:10+00:00

commit c6c209ceb87f64a6ceebe61761951dcbbf4a0baa upstream. I haven't found an NFSERR_EAGAIN in RFCs 1094, 1813, 7530, or 8881. None of these RFCs have an NFS status code that match the numeric value "11". Based on the meaning of the EAGAIN errno, I presume the use of this status in NFSD means NFS4ERR_DELAY. So replace the one usage of nfserr_eagain, and remove it from NFSD's NFS status conversion tables. As far as I can tell, NFSERR_EAGAIN has existed since the pre-git era, but was not actually used by any code until commit f4e44b393389 ("NFSD: delay unmount source's export after inter-server copy completed."), at which time it become possible for NFSD to return a status code of 11 (which is not valid NFS protocol). Fixes: f4e44b393389 ("NFSD: delay unmount source's export after inter-server copy completed.") Cc: stable@vger.kernel.org Reviewed-by: NeilBrown Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman