should_follow_link(): validate ->d_seq after having decided to follow

... otherwise d_is_symlink() above might have nothing to do with the inode value we've got. Cc: [email protected] # v4.2+ Signed-off-by: Al Viro <[email protected]>
kyagi · Feb 28, 2016 · a7f7754 · a7f7754
1 parent d456564
commit a7f7754
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/fs/namei.c b/fs/namei.c
@@ -1712,6 +1712,11 @@ static inline int should_follow_link(struct nameidata *nd, struct path *link,
 		return 0;
 	if (!follow)
 		return 0;
+	/* make sure that d_is_symlink above matches inode */
+	if (nd->flags & LOOKUP_RCU) {
+		if (read_seqcount_retry(&link->dentry->d_seq, seq))
+			return -ECHILD;
+	}
 	return pick_link(nd, link, inode, seq);
 }