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Message-ID: <20221114120349.472418-1-code@siddh.me>
Date: Mon, 14 Nov 2022 17:33:49 +0530
From: Siddh Raman Pant <code@...dh.me>
To: Gao Xiang <xiang@...nel.org>, Chao Yu <chao@...nel.org>,
Yue Hu <huyue2@...lpad.com>,
Jeffle Xu <jefflexu@...ux.alibaba.com>
Cc: linux-erofs <linux-erofs@...ts.ozlabs.org>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH] erofs/zmap.c: Bail out when no further region remains
The following calculation of iomap->length on line 798 in
z_erofs_iomap_begin_report() can yield 0:
if (iomap->offset >= inode->i_size)
iomap->length = length + map.m_la - offset;
This triggers a WARN_ON in iomap_iter_done() (see line 34 of
fs/iomap/iter.c).
Hence, return error when this scenario is encountered.
============================================================
This was reported as a crash by syzbot under an issue about
warning encountered in iomap_iter_done(), but unrelated to
erofs. Hence, not adding issue hash in Reported-by line.
C reproducer: https://syzkaller.appspot.com/text?tag=ReproC&x=1037a6b2880000
Kernel config: https://syzkaller.appspot.com/text?tag=KernelConfig&x=e2021a61197ebe02
Dashboard link: https://syzkaller.appspot.com/bug?extid=a8e049cd3abd342936b6
Reported-by: syzbot@...kaller.appspotmail.com
Signed-off-by: Siddh Raman Pant <code@...dh.me>
---
fs/erofs/zmap.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
index 0bb66927e3d0..bad852983eb9 100644
--- a/fs/erofs/zmap.c
+++ b/fs/erofs/zmap.c
@@ -796,6 +796,9 @@ static int z_erofs_iomap_begin_report(struct inode *inode, loff_t offset,
*/
if (iomap->offset >= inode->i_size)
iomap->length = length + map.m_la - offset;
+
+ if (iomap->length == 0)
+ return -EINVAL;
}
iomap->flags = 0;
return 0;
--
2.35.1
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