vfs: Fix O_NOFOLLOW behavior for paths with trailing slashes

According to specification

	mkdir d; ln -s d a; open("a/", O_NOFOLLOW | O_RDONLY)

should return success but currently it returns ELOOP.  This is a
regression caused by path lookup cleanup patch series.

Fix the code to ignore O_NOFOLLOW in case the provided path has trailing
slashes.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Reported-by: Marius Tolzmann <tolzmann@molgen.mpg.de>
Acked-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/namei.c b/fs/namei.c
index a7dce91a7e42..16df7277a92e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1641,7 +1641,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
         if (nd->last.name[nd->last.len]) {
                 if (open_flag & O_CREAT)
                         goto exit;
-                nd->flags |= LOOKUP_DIRECTORY;
+                nd->flags |= LOOKUP_DIRECTORY | LOOKUP_FOLLOW;
         }
 
         /* just plain open? */
@@ -1830,6 +1830,8 @@ reval:
         }
         if (open_flag & O_DIRECTORY)
                 nd.flags |= LOOKUP_DIRECTORY;
+        if (!(open_flag & O_NOFOLLOW))
+                nd.flags |= LOOKUP_FOLLOW;
         filp = do_last(&nd, &path, open_flag, acc_mode, mode, pathname);
         while (unlikely(!filp)) { /* trailing symlink */
                 struct path holder;
@@ -1837,7 +1839,7 @@ reval:
                 void *cookie;
                 error = -ELOOP;
                 /* S_ISDIR part is a temporary automount kludge */
-                if ((open_flag & O_NOFOLLOW) && !S_ISDIR(inode->i_mode))
+                if (!(nd.flags & LOOKUP_FOLLOW) && !S_ISDIR(inode->i_mode))
                         goto exit_dput;
                 if (count++ == 32)
                         goto exit_dput;