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Commit 77b9d059 authored by Nick Piggin's avatar Nick Piggin Committed by Jens Axboe
Browse files

writeback: Fix bdi use after free in wb_work_complete() 



By the time bdi_work_on_stack gets evaluated again in bdi_work_free, it
can already have been deallocated and used for something else in the
!on stack case, giving a false positive in this test and causing
corruption.

Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 77fad5e6

fs/fs-writeback.c

+3 −2
Original line number Diff line number Diff line
@@ -113,6 +113,7 @@ static void bdi_work_free(struct rcu_head *head) 
static void wb_work_complete(struct bdi_work *work)

{

	const enum writeback_sync_modes sync_mode = work->args.sync_mode;

	int onstack = bdi_work_on_stack(work);



	/*

	 * For allocated work, we can clear the done/seen bit right here.
@@ -120,9 +121,9 @@ static void wb_work_complete(struct bdi_work *work) 
	 * to after the RCU grace period, since the stack could be invalidated

	 * as soon as bdi_work_clear() has done the wakeup.

	 */

	if (!bdi_work_on_stack(work))

	if (!onstack)

		bdi_work_clear(work);

	if (sync_mode == WB_SYNC_NONE || bdi_work_on_stack(work))

	if (sync_mode == WB_SYNC_NONE || onstack)

		call_rcu(&work->rcu_head, bdi_work_free);

}