[PATCH 6.1 0177/1146] erofs: validate the extent length for uncompressed pclusters

Greg Kroah-Hartman
2022-12-28T15:21:36Z

From: Gao Xiang <hsiangkao@linux.alibaba.com>

[ Upstream commit c505feba4c0d76084e56ec498ce819f02a7043ae ]

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: 02827e1796b3 ("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
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/erofs/zmap.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
index f49295b9f2e1..e6d5d7a18fb0 100644
--- a/fs/erofs/zmap.c
+++ b/fs/erofs/zmap.c
@@ -698,6 +698,11 @@ static int z_erofs_do_map_blocks(struct inode *inode,
}

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)
map->m_algorithmformat =
Z_EROFS_COMPRESSION_INTERLACED;
--
2.35.1