reiserfs: update reiserfs_xattrs_initialized() condition

syzbot is reporting NULL pointer dereference at reiserfs_security_init()
[1], for commit 0cdf864f1d2d71e0 ("reiserfs: fixup xattr_root caching")
is assuming that REISERFS_SB(s)->xattr_root != NULL in
reiserfs_xattr_jcreate_nblocks() despite that commit made
REISERFS_SB(sb)->priv_root != NULL && REISERFS_SB(s)->xattr_root == NULL
case possible.

I guess that commit 71eb641c6e89836d ("reiserfs: fix oops while creating
privroot with selinux enabled") wanted to check xattr_root != NULL
before reiserfs_xattr_jcreate_nblocks(), for the changelog is talking
about the xattr root.

  The issue is that while creating the privroot during mount
  reiserfs_security_init calls reiserfs_xattr_jcreate_nblocks which
  dereferences the xattr root. The xattr root doesn't exist, so we get
  an oops.

Therefore, update reiserfs_xattrs_initialized() to check both the
privroot and the xattr root.

Link: https://syzkaller.appspot.com/bug?id=8abaedbdeb32c861dc5340544284167dd0e46cde
Reported-and-tested-by: syzbot <syzbot+690cb1e51970435f9775@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: 71eb641c6e89 ("reiserfs: fix oops while creating privroot with selinux enabled")
Acked-by: Jeff Mahoney <jeffm@suse.com>
Acked-by: Jan Kara <jack@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/reiserfs/xattr.h b/fs/reiserfs/xattr.h
index 9b3b06da568c8cb470514016dd58a78d37290565..e47fde1182de0efe35e27571edc877ff7ed41449 100644 (file)
--- a/fs/reiserfs/xattr.h
+++ b/fs/reiserfs/xattr.h
@@ -44,7 +44,7 @@ void reiserfs_security_free(struct reiserfs_security_handle *sec);
 
 static inline int reiserfs_xattrs_initialized(struct super_block *sb)
 {
-       return REISERFS_SB(sb)->priv_root != NULL;
+       return REISERFS_SB(sb)->priv_root && REISERFS_SB(sb)->xattr_root;
 }
 
 #define xattr_size(size) ((size) + sizeof(struct reiserfs_xattr_header))