exfat: fix uninit-value in __exfat_get_dentry_set

commit 02dffe9ab092fc4c8800aee68cb7eafd37a980c4 upstream.

There is no check if stream size and start_clu are invalid.
If start_clu is EOF cluster and stream size is 4096, It will
cause uninit value access. because ei->hint_femp.eidx could
be 128(if cluster size is 4K) and wrong hint will allocate
next cluster. and this cluster will be same with the cluster
that is allocated by exfat_extend_valid_size(). The previous
patch will check invalid start_clu, but for clarity, initialize
hint_femp.eidx to zero.

Cc: stable@vger.kernel.org
Reported-by: syzbot+01218003be74b5e1213a@syzkaller.appspotmail.com
Tested-by: syzbot+01218003be74b5e1213a@syzkaller.appspotmail.com
Reviewed-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c
index 631ad9e8e32a913037e468a49585b0dc4006b66f..9ae2a3d6cfe200543a1301923cd471b00febf72f 100644 (file)
--- a/fs/exfat/namei.c
+++ b/fs/exfat/namei.c
@@ -345,6 +345,7 @@ static int exfat_find_empty_entry(struct inode *inode,
                if (ei->start_clu == EXFAT_EOF_CLUSTER) {
                        ei->start_clu = clu.dir;
                        p_dir->dir = clu.dir;
+                       hint_femp.eidx = 0;
                }
 
                /* append to the FAT chain */