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Subject[PATCH] ext4: check iomap type only if ext4_iomap_begin() does not fail
Date
When ext4_iomap_overwrite_begin() calls ext4_iomap_begin() map blocks may
fail for some reason (e.g. memory allocation failure, bare disk write), and
later because "iomap->type ! = IOMAP_MAPPED" triggers WARN_ON(). When ext4
iomap_begin() returns an error, it is normal that the type of iomap->type
may not match the expectation. Therefore, we only determine if iomap->type
is as expected when ext4_iomap_begin() is executed successfully.

Reported-by: syzbot+08106c4b7d60702dbc14@syzkaller.appspotmail.com
Link: https://lore.kernel.org/all/00000000000015760b05f9b4eee9@google.com
Signed-off-by: Baokun Li <libaokun1@huawei.com>
---
fs/ext4/inode.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0d5ba922e411..19c884abe52b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3375,7 +3375,7 @@ static int ext4_iomap_overwrite_begin(struct inode *inode, loff_t offset,
*/
flags &= ~IOMAP_WRITE;
ret = ext4_iomap_begin(inode, offset, length, flags, iomap, srcmap);
- WARN_ON_ONCE(iomap->type != IOMAP_MAPPED);
+ WARN_ON_ONCE(!ret && iomap->type != IOMAP_MAPPED);
return ret;
}

--
2.31.1
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