[PATCH 6.0 0169/1073] erofs: validate the extent length for uncompressed pclusters

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From: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>

[ 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@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 02827e1796b3 ("staging: erofs: add erofs_map_blocks_iter")
Reviewed-by: Chao Yu <chao@xxxxxxxxxx>
Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20221205150050.47784-2-hsiangkao@xxxxxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/erofs/zmap.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
index a2a44c11bb64..720d74b5c699 100644
--- a/fs/erofs/zmap.c
+++ b/fs/erofs/zmap.c
@@ -677,6 +677,11 @@ 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






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