linux-kernel - [PATCH v2] erofs: fix general protection fault when reading fragment

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Date:   Fri, 21 Oct 2022 16:53:25 +0800
From:   Yue Hu <zbestahu@...il.com>
To:     xiang@...nel.org, chao@...nel.org
Cc:     linux-erofs@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        syzbot+3faecbfd845a895c04cb@...kaller.appspotmail.com,
        syzkaller-bugs@...glegroups.com, zhangwen@...lpad.com,
        Yue Hu <huyue2@...lpad.com>
Subject: [PATCH v2] erofs: fix general protection fault when reading fragment

From: Yue Hu <huyue2@...lpad.com>

As syzbot reported [1], the fragment feature sb flag is not set, so
packed_inode != NULL needs to be checked in z_erofs_read_fragment().

[1] https://lore.kernel.org/all/0000000000002e7a8905eb841ddd@google.com/

Reported-by: syzbot+3faecbfd845a895c04cb@...kaller.appspotmail.com
Fixes: 08a0c9ef3e7e ("erofs: support on-disk compressed fragments data")
Signed-off-by: Yue Hu <huyue2@...lpad.com>
---
v2: fix return value to -EFSCURRUPTED (Xiang)

 fs/erofs/zdata.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index cce56dde135c..55c13cd6934b 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -659,6 +659,9 @@ static int z_erofs_read_fragment(struct inode *inode, erofs_off_t pos,
 	u8 *src, *dst;
 	unsigned int i, cnt;
 
+	if (!packed_inode)
+		return -EFSCORRUPTED;
+
 	pos += EROFS_I(inode)->z_fragmentoff;
 	for (i = 0; i < len; i += cnt) {
 		cnt = min_t(unsigned int, len - i,
-- 
2.17.1