[PATCH] erofs: fix general protection fault when reading fragment

[Yue Hu]

From: Yue Hu <huyue2 at coolpad.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 at syzkaller.appspotmail.com
Fixes: 08a0c9ef3e7e ("erofs: support on-disk compressed fragments data")
Signed-off-by: Yue Hu <huyue2 at coolpad.com>
---
 fs/erofs/zdata.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index cce56dde135c..310f6916787a 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 -EFAULT;
+
 	pos += EROFS_I(inode)->z_fragmentoff;
 	for (i = 0; i < len; i += cnt) {
 		cnt = min_t(unsigned int, len - i,
-- 
2.17.1