From d7061627d701c90e1cac1e1e60c45292f64f3470 Mon Sep 17 00:00:00 2001 From: Xiongfeng Wang Date: Fri, 17 Dec 2021 15:30:55 +0000 Subject: iommu/iova: Fix race between FQ timeout and teardown It turns out to be possible for hotplugging out a device to reach the stage of tearing down the device's group and default domain before the domain's flush queue has drained naturally. At this point, it is then possible for the timeout to expire just before the del_timer() call in free_iova_flush_queue(), such that we then proceed to free the FQ resources while fq_flush_timeout() is still accessing them on another CPU. Crashes due to this have been observed in the wild while removing NVMe devices. Close the race window by using del_timer_sync() to safely wait for any active timeout handler to finish before we start to free things. We already avoid any locking in free_iova_flush_queue() since the FQ is supposed to be inactive anyway, so the potential deadlock scenario does not apply. Fixes: 9a005a800ae8 ("iommu/iova: Add flush timer") Reviewed-by: John Garry Signed-off-by: Xiongfeng Wang [ rm: rewrite commit message ] Signed-off-by: Robin Murphy Link: https://lore.kernel.org/r/0a365e5b07f14b7344677ad6a9a734966a8422ce.1639753638.git.robin.murphy@arm.com Signed-off-by: Joerg Roedel --- drivers/iommu/iova.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'drivers/iommu') diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c index ff567cbc42f7..670211e41771 100644 --- a/drivers/iommu/iova.c +++ b/drivers/iommu/iova.c @@ -83,8 +83,7 @@ static void free_iova_flush_queue(struct iova_domain *iovad) if (!has_iova_flush_queue(iovad)) return; - if (timer_pending(&iovad->fq_timer)) - del_timer(&iovad->fq_timer); + del_timer_sync(&iovad->fq_timer); fq_destroy_all_entries(iovad); -- cgit v1.2.3