kernel.git/fs/nfsd/export.c, branch linux-6.15.y

nfsd: fix access checking for NLM under XPRTSEC policies

2025-06-27T10:12:57Z

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 UAF when access ex_uuid or ex_stats

2025-01-06T14:37:42Z

We can access exp->ex_stats or exp->ex_uuid in rcu context(c_show and e_show). All these resources should be released using kfree_rcu. Fix this by using call_rcu, clean them all after a rcu grace period. ================================================================== 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 Fixes: ae74136b4bb6 ("SUNRPC: Allow cache lookups to use RCU protection rather than the r/w spinlock") Signed-off-by: Yang Erkun Reviewed-by: NeilBrown Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

nfsd: no need get cache ref when protected by rcu

2025-01-06T14:37:41Z

rcu_read_lock/rcu_read_unlock has already provide protection for the pointer we will reference when we call e_show. Therefore, there is no need to obtain a cache reference to help protect cache_head. Additionally, the .put such as expkey_put/svc_export_put will invoke dput, which can sleep and break rcu. Stop get cache reference to fix them all. Fixes: ae74136b4bb6 ("SUNRPC: Allow cache lookups to use RCU protection rather than the r/w spinlock") Suggested-by: NeilBrown Signed-off-by: Yang Erkun Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

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

2024-12-17T14:45:23Z

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

nfsd: release svc_expkey/svc_export with rcu_work

2024-11-19T01:23:05Z

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

nfsd: make sure exp active before svc_export_show

2024-11-19T01:23:05Z

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

nfsd: Fix NFSD_MAY_BYPASS_GSS and NFSD_MAY_BYPASS_GSS_ON_ROOT

2024-11-19T01:22:59Z

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

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

2024-09-23T19:03:29Z

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.

2024-09-20T23:31:03Z

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()

2024-09-20T23:31:03Z

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