Commit c505feba authored Dec 05, 2022 by Gao Xiang

erofs: validate the extent length for uncompressed pclusters

syzkaller reported a KASAN use-after-free:
https://syzkaller.appspot.com/bug?extid=2ae90e873e97f1faf6f2



The referenced fuzzed image actually has two issues:
 - m_pa == 0 as a non-inlined pcluster;
 - The logical length is longer than its physical length.

The first issue has already been addressed.  This patch addresses
the second issue by checking the extent length validity.

Reported-by:  <syzbot+2ae90e873e97f1faf6f2@syzkaller.appspotmail.com>
Fixes: 02827e17 ("staging: erofs: add erofs_map_blocks_iter")
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20221205150050.47784-2-hsiangkao@linux.alibaba.com

parent d5d188b8

fs/erofs/zmap.c

+5 −0

Original line number	Original line	Diff line number	Diff line
	@@ -698,6 +698,11 @@ static int z_erofs_do_map_blocks(struct inode *inode,
	}		}

	if (m.headtype == Z_EROFS_VLE_CLUSTER_TYPE_PLAIN) {		if (m.headtype == Z_EROFS_VLE_CLUSTER_TYPE_PLAIN) {
			if (map->m_llen > map->m_plen) {
			DBG_BUGON(1);
			err = -EFSCORRUPTED;
			goto unmap_out;
			}
	if (vi->z_advise & Z_EROFS_ADVISE_INTERLACED_PCLUSTER)		if (vi->z_advise & Z_EROFS_ADVISE_INTERLACED_PCLUSTER)
	map->m_algorithmformat =		map->m_algorithmformat =
	Z_EROFS_COMPRESSION_INTERLACED;		Z_EROFS_COMPRESSION_INTERLACED;