nfsd: fix NULL dereference in nfsd_statfs()

The commit ebabe9a9001af0af56c0c2780ca1576246e7a74b
    pass a struct path to vfs_statfs
introduced the struct path initialization, and this seems to trigger
an Oops on my machine.

fh_dentry field may be NULL and set later in fh_verify(), thus the
initialization of path must be after fh_verify().

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 96360a83cb91..661a6cf8e826 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -2033,15 +2033,17 @@ out:
 __be32
 nfsd_statfs(struct svc_rqst *rqstp, struct svc_fh *fhp, struct kstatfs *stat, int access)
 {
-        struct path path = {
-                .mnt    = fhp->fh_export->ex_path.mnt,
-                .dentry = fhp->fh_dentry,
-        };
         __be32 err;
 
         err = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP | access);
-        if (!err && vfs_statfs(&path, stat))
-                err = nfserr_io;
+        if (!err) {
+                struct path path = {
+                        .mnt    = fhp->fh_export->ex_path.mnt,
+                        .dentry = fhp->fh_dentry,
+                };
+                if (vfs_statfs(&path, stat))
+                        err = nfserr_io;
+        }
         return err;
 }