nfsd: racy access to ->d_name in nsfd4_encode_path()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 8 insertions, 6 deletions

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index c2a4701d7286..d9454fe5653f 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1816,10 +1816,7 @@ static __be32 nfsd4_encode_fs_location4(struct nfsd4_fs_location *location,
 static __be32 nfsd4_encode_path(const struct path *root,
                 const struct path *path, __be32 **pp, int *buflen)
 {
-        struct path cur = {
-                .mnt = path->mnt,
-                .dentry = path->dentry,
-        };
+        struct path cur = *path;
         __be32 *p = *pp;
         struct dentry **components = NULL;
         unsigned int ncomponents = 0;
@@ -1859,14 +1856,19 @@ static __be32 nfsd4_encode_path(const struct path *root,
 
         while (ncomponents) {
                 struct dentry *dentry = components[ncomponents - 1];
-                unsigned int len = dentry->d_name.len;
+                unsigned int len;
 
+                spin_lock(&dentry->d_lock);
+                len = dentry->d_name.len;
                 *buflen -= 4 + (XDR_QUADLEN(len) << 2);
-                if (*buflen < 0)
+                if (*buflen < 0) {
+                        spin_unlock(&dentry->d_lock);
                         goto out_free;
+                }
                 WRITE32(len);
                 WRITEMEM(dentry->d_name.name, len);
                 dprintk("/%s", dentry->d_name.name);
+                spin_unlock(&dentry->d_lock);
                 dput(dentry);
                 ncomponents--;
         }