[PATCH] ext4: fix buffer_head leak in ext4_init_orphan_info

[Guanghui Yang]

ext4_init_orphan_info() reads orphan file blocks with ext4_bread()
and stores the returned buffer_head in oi->of_binfo[i].ob_bh.

If ext4_bread() succeeds but the orphan block magic or checksum
validation fails, the function jumps to out_free. However, out_free
starts releasing buffers from i - 1, so the current buffer_head at
index i is skipped.

This leaks the buffer_head reference obtained by ext4_bread() on the
bad magic and bad checksum error paths.

Fix this by tracking the number of successfully read buffer_heads and
releasing exactly those buffer_heads on the error path.

Fixes: 02f310fcf47f ("ext4: Speedup ext4 orphan inode handling")
Signed-off-by: Guanghui Yang <3497809730@xxxxxx>
---
 fs/ext4/orphan.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/orphan.c b/fs/ext4/orphan.c
index 64ea47624233..baa11e079185 100644
--- a/fs/ext4/orphan.c
+++ b/fs/ext4/orphan.c
@@ -572,6 +572,7 @@ int ext4_init_orphan_info(struct super_block *sb)
 	int i, j;
 	int ret;
 	int free;
+	int loaded = 0;
 	__le32 *bdata;
 	int inodes_per_ob = ext4_inodes_per_orphan_block(sb);
 	struct ext4_orphan_block_tail *ot;
@@ -613,6 +614,7 @@ int ext4_init_orphan_info(struct super_block *sb)
 			ret = -EIO;
 			goto out_free;
 		}
+		loaded++;
 		ot = ext4_orphan_block_tail(sb, oi->of_binfo[i].ob_bh);
 		if (le32_to_cpu(ot->ob_magic) != EXT4_ORPHAN_BLOCK_MAGIC) {
 			ext4_error(sb, "orphan file block %d: bad magic", i);
@@ -635,8 +637,8 @@ int ext4_init_orphan_info(struct super_block *sb)
 	iput(inode);
 	return 0;
 out_free:
-	for (i--; i >= 0; i--)
-		brelse(oi->of_binfo[i].ob_bh);
+	while (loaded-- > 0)
+		brelse(oi->of_binfo[loaded].ob_bh);
 	kvfree(oi->of_binfo);
 out_put:
 	iput(inode);
-- 
2.34.1