This is a note to let you know that I've just added the patch titled
iommu/iova: Fix race between FQ timeout and teardown
to the 5.16-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
iommu-iova-fix-race-between-fq-timeout-and-teardown.patch
and it can be found in the queue-5.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 4b6514c4d2f95966544fce7e9a0f505f07e28eef
Author: Xiongfeng Wang <wangxiongfeng2@xxxxxxxxxx>
Date: Fri Dec 17 15:30:55 2021 +0000
iommu/iova: Fix race between FQ timeout and teardown
[ Upstream commit d7061627d701c90e1cac1e1e60c45292f64f3470 ]
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 <john.garry@xxxxxxxxxx>
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@xxxxxxxxxx>
[ rm: rewrite commit message ]
Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
Link: https://lore.kernel.org/r/0a365e5b07f14b7344677ad6a9a734966a8422ce.1639753638.git.robin.murphy@xxxxxxx
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 9e8bc802ac053..920fcc27c9a1e 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);
