From 77b9d059cb3ddb8b1246d5878e81d52926550b23 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Tue, 15 Sep 2009 21:34:51 +0200 Subject: [PATCH] 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: Nick Piggin Signed-off-by: Jens Axboe --- fs/fs-writeback.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 6bca6f8176f..7eba7326b9b 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -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); }