do_lookup() fix

do_lookup() has a path leading from LOOKUP_RCU case to non-RCU
crossing of mountpoints, which breaks things badly.  If we
hit need_revalidate: and do nothing in there, we need to come
back into LOOKUP_RCU half of things, not to done: in non-RCU
one.

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

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 8df7a78ace58..529e917ad2fc 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1089,6 +1089,7 @@ static int do_lookup(struct nameidata *nd, struct qstr *name,
                 nd->seq = seq;
                 if (dentry->d_flags & DCACHE_OP_REVALIDATE)
                         goto need_revalidate;
+done2:
                 path->mnt = mnt;
                 path->dentry = dentry;
                 __follow_mount_rcu(nd, path, inode);
@@ -1143,6 +1144,8 @@ need_revalidate:
                 goto need_lookup;
         if (IS_ERR(dentry))
                 goto fail;
+        if (nd->flags & LOOKUP_RCU)
+                goto done2;
         goto done;
 
 fail: