This is a note to let you know that I've just added the patch titled
blk-mq: Avoid race condition with uninitialized requests
to the 3.16-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:
blk-mq-avoid-race-condition-with-uninitialized-requests.patch
and it can be found in the queue-3.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 683d0e126232d898a481daa3a4ca032c2b1a9660 Mon Sep 17 00:00:00 2001
From: David Hildenbrand <dahi@xxxxxxxxxxxxxxxxxx>
Date: Thu, 18 Sep 2014 11:04:31 +0200
Subject: blk-mq: Avoid race condition with uninitialized requests
From: David Hildenbrand <dahi@xxxxxxxxxxxxxxxxxx>
commit 683d0e126232d898a481daa3a4ca032c2b1a9660 upstream.
This patch should fix the bug reported in
https://lkml.org/lkml/2014/9/11/249.
We have to initialize at least the atomic_flags and the cmd_flags when
allocating storage for the requests.
Otherwise blk_mq_timeout_check() might dereference uninitialized
pointers when racing with the creation of a request.
Also move the reset of cmd_flags for the initializing code to the point
where a request is freed. So we will never end up with pending flush
request indicators that might trigger dereferences of invalid pointers
in blk_mq_timeout_check().
Signed-off-by: David Hildenbrand <dahi@xxxxxxxxxxxxxxxxxx>
Reported-by: Paulo De Rezende Pinatti <ppinatti@xxxxxxxxxxxxxxxxxx>
Tested-by: Paulo De Rezende Pinatti <ppinatti@xxxxxxxxxxxxxxxxxx>
Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
block/blk-mq.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -219,7 +219,6 @@ __blk_mq_alloc_request(struct blk_mq_all
if (tag != BLK_MQ_TAG_FAIL) {
rq = data->hctx->tags->rqs[tag];
- rq->cmd_flags = 0;
if (blk_mq_tag_busy(data->hctx)) {
rq->cmd_flags = REQ_MQ_INFLIGHT;
atomic_inc(&data->hctx->nr_active);
@@ -274,6 +273,7 @@ static void __blk_mq_free_request(struct
if (rq->cmd_flags & REQ_MQ_INFLIGHT)
atomic_dec(&hctx->nr_active);
+ rq->cmd_flags = 0;
clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
blk_mq_put_tag(hctx, tag, &ctx->last_tag);
@@ -1411,6 +1411,8 @@ static struct blk_mq_tags *blk_mq_init_r
left -= to_do * rq_size;
for (j = 0; j < to_do; j++) {
tags->rqs[i] = p;
+ tags->rqs[i]->atomic_flags = 0;
+ tags->rqs[i]->cmd_flags = 0;
if (set->ops->init_request) {
if (set->ops->init_request(set->driver_data,
tags->rqs[i], hctx_idx, i,
Patches currently in stable-queue which might be from dahi@xxxxxxxxxxxxxxxxxx are
queue-3.16/kvm-s390-fix-user-triggerable-bug-in-dead-code.patch
queue-3.16/blk-mq-avoid-race-condition-with-uninitialized-requests.patch
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