linux-kernel - [PATCH] erofs: refuse crafted out-of-file-range encoded extents

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Message-ID: <20250619032839.2642193-1-hsiangkao@linux.alibaba.com>
Date: Thu, 19 Jun 2025 11:28:39 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: linux-erofs@...ts.ozlabs.org
Cc: LKML <linux-kernel@...r.kernel.org>,
	Gao Xiang <hsiangkao@...ux.alibaba.com>,
	syzbot+d8f000c609f05f52d9b5@...kaller.appspotmail.com
Subject: [PATCH] erofs: refuse crafted out-of-file-range encoded extents

Crafted encoded extents could record out-of-range `lstart`, which should
not happen in normal cases.

It caused an iomap_iter_done() complaint [1] reported by syzbot.

[1] https://lore.kernel.org/r/684cb499.a00a0220.c6bd7.0010.GAE@google.com
Fixes: 1d191b4ca51d ("erofs: implement encoded extent metadata")
Reported-by: syzbot+d8f000c609f05f52d9b5@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d8f000c609f05f52d9b5
Signed-off-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
---
 fs/erofs/zmap.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
index 14ea47f954f5..6afcb054780d 100644
--- a/fs/erofs/zmap.c
+++ b/fs/erofs/zmap.c
@@ -597,6 +597,10 @@ static int z_erofs_map_blocks_ext(struct inode *inode,
 
 			if (la > map->m_la) {
 				r = mid;
+				if (la > lend) {
+					DBG_BUGON(1);
+					return -EFSCORRUPTED;
+				}
 				lend = la;
 			} else {
 				l = mid + 1;
-- 
2.43.5