kernel/linux.git/fs/nfsd/export.c, branch v6.12.102

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

2026-01-08T09:14:24+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

nfsd: decouple the xprtsec policy check from check_nfsd_access()

2025-10-19T14:34:07+00:00

commit e4f574ca9c6dfa66695bb054ff5df43ecea873ec upstream. A while back I had reported that an NFSv3 client could successfully mount using '-o xprtsec=none' an export that had been exported with 'xprtsec=tls:mtls'. By "successfully" I mean that the mount command would succeed and the mount would show up in /proc/mount. Attempting to do anything futher with the mount would be met with NFS3ERR_ACCES. This was fixed (albeit accidentally) by commit bb4f07f2409c ("nfsd: Fix NFSD_MAY_BYPASS_GSS and NFSD_MAY_BYPASS_GSS_ON_ROOT") and was subsequently re-broken by commit 0813c5f01249 ("nfsd: fix access checking for NLM under XPRTSEC policies"). Transport Layer Security isn't an RPC security flavor or pseudo-flavor, so we shouldn't be conflating them when determining whether the access checks can be bypassed. Split check_nfsd_access() into two helpers, and have __fh_verify() call the helpers directly since __fh_verify() has logic that allows one or both of the checks to be skipped. All other sites will continue to call check_nfsd_access(). Link: https://lore.kernel.org/linux-nfs/ZjO3Qwf_G87yNXb2@aion/ Fixes: 9280c5774314 ("NFSD: Handle new xprtsec= export option") Cc: stable@vger.kernel.org Signed-off-by: Scott Mayhew Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman

nfsd: fix access checking for NLM under XPRTSEC policies

2025-10-19T14:34:06+00:00

commit 0813c5f01249dbc32ccbc68d27a24fde5bf2901c upstream. When an export policy with xprtsec policy is set with "tls" and/or "mtls", but an NFS client is doing a v3 xprtsec=tls mount, then NLM locking calls fail with an error because there is currently no support for NLM with TLS. Until such support is added, allow NLM calls under TLS-secured policy. Fixes: 4cc9b9f2bf4d ("nfsd: refine and rename NFSD_MAY_LOCK") Cc: stable@vger.kernel.org Signed-off-by: Olga Kornievskaia Reviewed-by: NeilBrown Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman

nfsd: Fix NFSD_MAY_BYPASS_GSS and NFSD_MAY_BYPASS_GSS_ON_ROOT

2025-10-19T14:34:03+00:00

[ Upstream commit bb4f07f2409c26c01e97e6f9b432545f353e3b66 ] Currently NFSD_MAY_BYPASS_GSS and NFSD_MAY_BYPASS_GSS_ON_ROOT do not bypass only GSS, but bypass any method. This is a problem specially for NFS3 AUTH_NULL-only exports. The purpose of NFSD_MAY_BYPASS_GSS_ON_ROOT is described in RFC 2623, section 2.3.2, to allow mounting NFS2/3 GSS-only export without authentication. So few procedures which do not expose security risk used during mount time can be called also with AUTH_NONE or AUTH_SYS, to allow client mount operation to finish successfully. The problem with current implementation is that for AUTH_NULL-only exports, the NFSD_MAY_BYPASS_GSS_ON_ROOT is active also for NFS3 AUTH_UNIX mount attempts which confuse NFS3 clients, and make them think that AUTH_UNIX is enabled and is working. Linux NFS3 client never switches from AUTH_UNIX to AUTH_NONE on active mount, which makes the mount inaccessible. Fix the NFSD_MAY_BYPASS_GSS and NFSD_MAY_BYPASS_GSS_ON_ROOT implementation and really allow to bypass only exports which have enabled some real authentication (GSS, TLS, or any other). The result would be: For AUTH_NULL-only export if client attempts to do mount with AUTH_UNIX flavor then it will receive access errors, which instruct client that AUTH_UNIX flavor is not usable and will either try other auth flavor (AUTH_NULL if enabled) or fails mount procedure. Similarly if client attempt to do mount with AUTH_NULL flavor and only AUTH_UNIX flavor is enabled then the client will receive access error. This should fix problems with AUTH_NULL-only or AUTH_UNIX-only exports if client attempts to mount it with other auth flavor (e.g. with AUTH_NULL for AUTH_UNIX-only export, or with AUTH_UNIX for AUTH_NULL-only export). Signed-off-by: Pali Rohár Reviewed-by: NeilBrown Signed-off-by: Chuck Lever Stable-dep-of: 898374fdd7f0 ("nfsd: unregister with rpcbind when deleting a transport") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

nfsd: Revert "nfsd: release svc_expkey/svc_export with rcu_work"

2025-01-02T09:34:11+00:00

[ Upstream commit 69d803c40edeaf94089fbc8751c9b746cdc35044 ] This reverts commit f8c989a0c89a75d30f899a7cabdc14d72522bb8d. Before this commit, svc_export_put or expkey_put will call path_put with sync mode. After this commit, path_put will be called with async mode. And this can lead the unexpected results show as follow. mkfs.xfs -f /dev/sda echo "/ *(rw,no_root_squash,fsid=0)" > /etc/exports echo "/mnt *(rw,no_root_squash,fsid=1)" >> /etc/exports exportfs -ra service nfs-server start mount -t nfs -o vers=4.0 127.0.0.1:/mnt /mnt1 mount /dev/sda /mnt/sda touch /mnt1/sda/file exportfs -r umount /mnt/sda # failed unexcepted The touch will finally call nfsd_cross_mnt, add refcount to mount, and then add cache_head. Before this commit, exportfs -r will call cache_flush to cleanup all cache_head, and path_put in svc_export_put/expkey_put will be finished with sync mode. So, the latter umount will always success. However, after this commit, path_put will be called with async mode, the latter umount may failed, and if we add some delay, umount will success too. Personally I think this bug and should be fixed. We first revert before bugfix patch, and then fix the original bug with a different way. Fixes: f8c989a0c89a ("nfsd: release svc_expkey/svc_export with rcu_work") Signed-off-by: Yang Erkun Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

nfsd: make sure exp active before svc_export_show

2024-12-09T09:41:09+00:00

commit be8f982c369c965faffa198b46060f8853e0f1f0 upstream. The function `e_show` was called with protection from RCU. This only ensures that `exp` will not be freed. Therefore, the reference count for `exp` can drop to zero, which will trigger a refcount use-after-free warning when `exp_get` is called. To resolve this issue, use `cache_get_rcu` to ensure that `exp` remains active. ------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 3 PID: 819 at lib/refcount.c:25 refcount_warn_saturate+0xb1/0x120 CPU: 3 UID: 0 PID: 819 Comm: cat Not tainted 6.12.0-rc3+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 RIP: 0010:refcount_warn_saturate+0xb1/0x120 ... Call Trace: e_show+0x20b/0x230 [nfsd] seq_read_iter+0x589/0x770 seq_read+0x1e5/0x270 vfs_read+0x125/0x530 ksys_read+0xc1/0x160 do_syscall_64+0x5f/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e Fixes: bf18f163e89c ("NFSD: Using exp_get for export getting") Cc: stable@vger.kernel.org # 4.20+ Signed-off-by: Yang Erkun Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman

nfsd: release svc_expkey/svc_export with rcu_work

2024-12-05T13:02:26+00:00

[ Upstream commit f8c989a0c89a75d30f899a7cabdc14d72522bb8d ] The last reference for `cache_head` can be reduced to zero in `c_show` and `e_show`(using `rcu_read_lock` and `rcu_read_unlock`). Consequently, `svc_export_put` and `expkey_put` will be invoked, leading to two issues: 1. The `svc_export_put` will directly free ex_uuid. However, `e_show`/`c_show` will access `ex_uuid` after `cache_put`, which can trigger a use-after-free issue, shown below. ================================================================== BUG: KASAN: slab-use-after-free in svc_export_show+0x362/0x430 [nfsd] Read of size 1 at addr ff11000010fdc120 by task cat/870 CPU: 1 UID: 0 PID: 870 Comm: cat Not tainted 6.12.0-rc3+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 Call Trace: dump_stack_lvl+0x53/0x70 print_address_description.constprop.0+0x2c/0x3a0 print_report+0xb9/0x280 kasan_report+0xae/0xe0 svc_export_show+0x362/0x430 [nfsd] c_show+0x161/0x390 [sunrpc] seq_read_iter+0x589/0x770 seq_read+0x1e5/0x270 proc_reg_read+0xe1/0x140 vfs_read+0x125/0x530 ksys_read+0xc1/0x160 do_syscall_64+0x5f/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e Allocated by task 830: kasan_save_stack+0x20/0x40 kasan_save_track+0x14/0x30 __kasan_kmalloc+0x8f/0xa0 __kmalloc_node_track_caller_noprof+0x1bc/0x400 kmemdup_noprof+0x22/0x50 svc_export_parse+0x8a9/0xb80 [nfsd] cache_do_downcall+0x71/0xa0 [sunrpc] cache_write_procfs+0x8e/0xd0 [sunrpc] proc_reg_write+0xe1/0x140 vfs_write+0x1a5/0x6d0 ksys_write+0xc1/0x160 do_syscall_64+0x5f/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e Freed by task 868: kasan_save_stack+0x20/0x40 kasan_save_track+0x14/0x30 kasan_save_free_info+0x3b/0x60 __kasan_slab_free+0x37/0x50 kfree+0xf3/0x3e0 svc_export_put+0x87/0xb0 [nfsd] cache_purge+0x17f/0x1f0 [sunrpc] nfsd_destroy_serv+0x226/0x2d0 [nfsd] nfsd_svc+0x125/0x1e0 [nfsd] write_threads+0x16a/0x2a0 [nfsd] nfsctl_transaction_write+0x74/0xa0 [nfsd] vfs_write+0x1a5/0x6d0 ksys_write+0xc1/0x160 do_syscall_64+0x5f/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e 2. We cannot sleep while using `rcu_read_lock`/`rcu_read_unlock`. However, `svc_export_put`/`expkey_put` will call path_put, which subsequently triggers a sleeping operation due to the following `dput`. ============================= WARNING: suspicious RCU usage 5.10.0-dirty #141 Not tainted ----------------------------- ... Call Trace: dump_stack+0x9a/0xd0 ___might_sleep+0x231/0x240 dput+0x39/0x600 path_put+0x1b/0x30 svc_export_put+0x17/0x80 e_show+0x1c9/0x200 seq_read_iter+0x63f/0x7c0 seq_read+0x226/0x2d0 vfs_read+0x113/0x2c0 ksys_read+0xc9/0x170 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x67/0xd1 Fix these issues by using `rcu_work` to help release `svc_expkey`/`svc_export`. This approach allows for an asynchronous context to invoke `path_put` and also facilitates the freeing of `uuid/exp/key` after an RCU grace period. Fixes: 9ceddd9da134 ("knfsd: Allow lockless lookups of the exports") Signed-off-by: Yang Erkun Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

NFSD: Handle @rqstp == NULL in check_nfsd_access()

2024-09-23T19:03:29+00:00

LOCALIO-initiated open operations are not running in an nfsd thread and thus do not have an associated svc_rqst context. Signed-off-by: NeilBrown Co-developed-by: Mike Snitzer Signed-off-by: Mike Snitzer Signed-off-by: Chuck Lever Reviewed-by: Jeff Layton Signed-off-by: Anna Schumaker

nfsd: Move error code mapping to per-version proc code.

2024-09-20T23:31:03+00:00

There is code scattered around nfsd which chooses an error status based on the particular version of nfs being used. It is cleaner to have the version specific choices in version specific code. With this patch common code returns the most specific error code possible and the version specific code maps that if necessary. Both v2 (nfsproc.c) and v3 (nfs3proc.c) now have a "map_status()" function which is called to map the resp->status before each non-trivial nfsd_proc_* or nfsd3_proc_* function returns. NFS4ERR_SYMLINK and NFS4ERR_WRONG_TYPE introduce extra complications and are left for a later patch. Signed-off-by: NeilBrown Reviewed-by: Jeff Layton Reviewed-by: Christoph Hellwig Signed-off-by: Chuck Lever

nfsd: Don't pass all of rqst into rqst_exp_find()

2024-09-20T23:31:03+00:00

Rather than passing the whole rqst, pass the pieces that are actually needed. This makes the inputs to rqst_exp_find() more obvious. Signed-off-by: NeilBrown Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever