ceph: avoid possible null deref in readdir after dir llseek

last may be NULL, but we dereference it in the else branch without
checking.  Normally it doesn't trigger because last == NULL when fpos == 2,
but it could happen on a newly opened dir if the user seeks forward.

Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Sage Weil <sage@newdream.net>

diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index 7d447af84ec4861acee8cd82bcecf80a892132b1..158c700fdca5e4f62763377a8374217d6371b68b 100644 (file)
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -114,8 +114,8 @@ static int __dcache_readdir(struct file *filp,
        spin_lock(&dcache_lock);
 
        /* start at beginning? */
-       if (filp->f_pos == 2 || (last &&
-                                filp->f_pos < ceph_dentry(last)->offset)) {
+       if (filp->f_pos == 2 || last == NULL ||
+           filp->f_pos < ceph_dentry(last)->offset) {
                if (list_empty(&parent->d_subdirs))
                        goto out_unlock;
                p = parent->d_subdirs.prev;