[PATCH v4 3/9] ext4: check return value of ext4_get_block() in ext4_load_tail_bh()

[Zhang Yi]

From: Zhang Yi <yi.zhang@xxxxxxxxxx>

ext4_load_tail_bh() ignores the return value of ext4_get_block(), so an
I/O or allocation failure is silently discarded. buffer_mapped(bh) stays
false and the function returns NULL, which callers such as
ext4_block_do_zero_range() treat as "nothing to do" and return success.
This can mask real failures during zero-range, truncate, or punch-hole
operations, potentially exposing stale data if the block was not
actually a hole and needed zeroing. So propagate the error to the
callers.

Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
---
 fs/ext4/inode.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3ce925ca0769..77ec82fbda89 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4064,7 +4064,9 @@ static struct buffer_head *ext4_load_tail_bh(struct inode *inode, loff_t from)
 	}
 	if (!buffer_mapped(bh)) {
 		BUFFER_TRACE(bh, "unmapped");
-		ext4_get_block(inode, iblock, bh, 0);
+		err = ext4_get_block(inode, iblock, bh, 0);
+		if (err < 0)
+			goto unlock;
 		/* unmapped? It's a hole - nothing to do */
 		if (!buffer_mapped(bh)) {
 			BUFFER_TRACE(bh, "still unmapped");
-- 
2.52.0