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From: Bart Van Assche <bvanassche@acm.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
	Bart Van Assche <bvanassche@acm.org>,
	Christoph Hellwig <hch@infradead.org>,
	Ming Lei <ming.lei@redhat.com>, Hannes Reinecke <hare@suse.com>,
	Johannes Thumshirn <jth@kernel.org>,
	Keith Busch <kbusch@kernel.org>
Subject: [PATCH 3/5] blk-mq: Fix a recently introduced regression in blk_mq_realloc_hw_ctxs()
Date: Mon, 17 Feb 2020 13:08:37 -0800	[thread overview]
Message-ID: <20200217210839.28535-4-bvanassche@acm.org> (raw)
In-Reply-To: <20200217210839.28535-1-bvanassche@acm.org>

q->nr_hw_queues must only be updated once it is known that
blk_mq_realloc_hw_ctxs() has succeeded. Otherwise it can happen that
reallocation fails and that q->nr_hw_queues is larger than the number of
allocated hardware queues. This patch fixes the following crash if
increasing the number of hardware queues fails:

BUG: KASAN: null-ptr-deref in blk_mq_map_swqueue+0x775/0x810
Write of size 8 at addr 0000000000000118 by task check/977

CPU: 3 PID: 977 Comm: check Not tainted 5.6.0-rc1-dbg+ #8
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
Call Trace:
 dump_stack+0xa5/0xe6
 __kasan_report.cold+0x65/0x99
 kasan_report+0x16/0x20
 check_memory_region+0x140/0x1b0
 memset+0x28/0x40
 blk_mq_map_swqueue+0x775/0x810
 blk_mq_update_nr_hw_queues+0x468/0x710
 nullb_device_submit_queues_store+0xf7/0x1a0 [null_blk]
 configfs_write_file+0x1c4/0x250 [configfs]
 __vfs_write+0x4c/0x90
 vfs_write+0x145/0x2c0
 ksys_write+0xd7/0x180
 __x64_sys_write+0x47/0x50
 do_syscall_64+0x6f/0x2f0
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jth@kernel.org>
Cc: Keith Busch <kbusch@kernel.org>
Fixes: ac0d6b926e74 ("block: Reduce the amount of memory required per request queue")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 block/blk-mq.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2b9f490f5a64..5408098b58f2 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2824,7 +2824,6 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
 			memcpy(new_hctxs, hctxs, q->nr_hw_queues *
 			       sizeof(*hctxs));
 		q->queue_hw_ctx = new_hctxs;
-		q->nr_hw_queues = set->nr_hw_queues;
 		kfree(hctxs);
 		hctxs = new_hctxs;
 	}

  parent reply	other threads:[~2020-02-17 21:08 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-17 21:08 [PATCH 0/5] Five patches related to changing the number of hardware queues Bart Van Assche
2020-02-17 21:08 ` [PATCH 1/5] blk-mq: Fix a comment in include/linux/blk-mq.h Bart Van Assche
2020-02-18  3:04   ` Ming Lei
2020-02-17 21:08 ` [PATCH 2/5] blk-mq: Keep set->nr_hw_queues and set->map[].nr_queues in sync Bart Van Assche
2020-02-18  3:16   ` Ming Lei
2020-02-19  4:24     ` Bart Van Assche
2020-02-17 21:08 ` Bart Van Assche [this message]
2020-02-18  3:45   ` [PATCH 3/5] blk-mq: Fix a recently introduced regression in blk_mq_realloc_hw_ctxs() Ming Lei
2020-02-17 21:08 ` [PATCH 4/5] null_blk: Suppress an UBSAN complaint triggered when setting 'memory_backed' Bart Van Assche
2020-02-17 21:08 ` [PATCH 5/5] null_blk: Fix changing the number of hardware queues Bart Van Assche

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