[PATCH v2] btrfs: fix transaction use-after-free in raid stripe insertion

[Shuangpeng Bai <shuangpeng.kernel@gmail.com>]

If allocation of a RAID stripe extent fails,
btrfs_insert_one_raid_extent() aborts and ends the transaction before
returning -ENOMEM.

btrfs_finish_one_ordered(), the production caller through
btrfs_insert_raid_extent(), still owns the transaction handle. It handles
the error by aborting the transaction and then reaches the common exit
path, which ends the transaction again.

The premature end can free the handle and drop its transaction reference.
Transaction cleanup can then free the transaction before the caller's
second abort accesses the handle and transaction, resulting in
use-after-free.

Keep the abort at the failure site, but let the caller's common exit path
end the transaction once, after it has finished using both objects.

Fixes: 02c372e1f016 ("btrfs: add support for inserting raid stripe extents")
Cc: stable@vger.kernel.org
Assisted-by: Codex:GPT-5
Signed-off-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
---
Changes in v2:
- Add the Assisted-by tag to disclose LLM usage.

v1: https://lore.kernel.org/r/20260817012733.2962781-1-shuangpeng.kernel@gmail.com

 fs/btrfs/raid-stripe-tree.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/btrfs/raid-stripe-tree.c b/fs/btrfs/raid-stripe-tree.c
index b210371ce91e..89e259a47d8d 100644
--- a/fs/btrfs/raid-stripe-tree.c
+++ b/fs/btrfs/raid-stripe-tree.c
@@ -337,7 +337,6 @@ int btrfs_insert_one_raid_extent(struct btrfs_trans_handle *trans,
 	stripe_extent = kzalloc(item_size, GFP_NOFS);
 	if (unlikely(!stripe_extent)) {
 		btrfs_abort_transaction(trans, -ENOMEM);
-		btrfs_end_transaction(trans);
 		return -ENOMEM;
 	}
 
-- 
2.43.0