diff options
| author | NeilBrown <neil@brown.name> | 2025-10-08 09:52:25 -0400 |
|---|---|---|
| committer | Chuck Lever <chuck.lever@oracle.com> | 2025-11-04 11:02:31 -0500 |
| commit | 8a7348a9ed70bda1c1f51d3f1815bcbdf9f3b38c (patch) | |
| tree | 4490e0bd7e6c162caa27c73322dec0135c2f9f72 | |
| parent | 3e7f011c255582d7c914133785bbba1990441713 (diff) | |
nfsd: fix refcount leak in nfsd_set_fh_dentry()
nfsd exports a "pseudo root filesystem" which is used by NFSv4 to find
the various exported filesystems using LOOKUP requests from a known root
filehandle. NFSv3 uses the MOUNT protocol to find those exported
filesystems and so is not given access to the pseudo root filesystem.
If a v3 (or v2) client uses a filehandle from that filesystem,
nfsd_set_fh_dentry() will report an error, but still stores the export
in "struct svc_fh" even though it also drops the reference (exp_put()).
This means that when fh_put() is called an extra reference will be dropped
which can lead to use-after-free and possible denial of service.
Normal NFS usage will not provide a pseudo-root filehandle to a v3
client. This bug can only be triggered by the client synthesising an
incorrect filehandle.
To fix this we move the assignments to the svc_fh later, after all
possible error cases have been detected.
Reported-and-tested-by: tianshuo han <hantianshuo233@gmail.com>
Fixes: ef7f6c4904d0 ("nfsd: move V4ROOT version check to nfsd_set_fh_dentry()")
Signed-off-by: NeilBrown <neil@brown.name>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
| -rw-r--r-- | fs/nfsd/nfsfh.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c index 3edccc38db42..bd9acfdc7b01 100644 --- a/fs/nfsd/nfsfh.c +++ b/fs/nfsd/nfsfh.c @@ -269,9 +269,6 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct net *net, dentry); } - fhp->fh_dentry = dentry; - fhp->fh_export = exp; - switch (fhp->fh_maxsize) { case NFS4_FHSIZE: if (dentry->d_sb->s_export_op->flags & EXPORT_OP_NOATOMIC_ATTR) @@ -293,6 +290,9 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct net *net, goto out; } + fhp->fh_dentry = dentry; + fhp->fh_export = exp; + return 0; out: exp_put(exp); |