ntfs: Fix panic about slab-out-of-bounds caused by ntfs_listxattr()

Here is a BUG report from syzbot:

BUG: KASAN: slab-out-of-bounds in ntfs_list_ea fs/ntfs3/xattr.c:191 [inline]
BUG: KASAN: slab-out-of-bounds in ntfs_listxattr+0x401/0x570 fs/ntfs3/xattr.c:710
Read of size 1 at addr ffff888021acaf3d by task syz-executor128/3632

Call Trace:
 ntfs_list_ea fs/ntfs3/xattr.c:191 [inline]
 ntfs_listxattr+0x401/0x570 fs/ntfs3/xattr.c:710
 vfs_listxattr fs/xattr.c:457 [inline]
 listxattr+0x293/0x2d0 fs/xattr.c:804

Fix the logic of ea_all iteration. When the ea->name_len is 0,
return immediately, or Add2Ptr() would visit invalid memory
in the next loop.

Fixes: be71b5cba2e6 ("fs/ntfs3: Add attrib operations")
Reported-by: syzbot+9fcea5ef6dc4dc72d334@syzkaller.appspotmail.com
Signed-off-by: Zeng Heng <zengheng4@huawei.com>
[almaz.alexandrovich@paragon-software.com: lines of the patch have changed]
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

diff --git a/fs/ntfs3/xattr.c b/fs/ntfs3/xattr.c
index c3de60a4543fa58d124ef4290bd5a2f2964d7cb3..fd02fcf4d4091669aba05add2c8999d578bc2e2b 100644 (file)
--- a/fs/ntfs3/xattr.c
+++ b/fs/ntfs3/xattr.c
@@ -214,6 +214,9 @@ static ssize_t ntfs_list_ea(struct ntfs_inode *ni, char *buffer,
                ea = Add2Ptr(ea_all, off);
                ea_size = unpacked_ea_size(ea);
 
+               if (!ea->name_len)
+                       break;
+
                if (buffer) {
                        if (ret + ea->name_len + 1 > bytes_per_buffer) {
                                err = -ERANGE;