From: Bart Van Assche bvanassche@acm.org
[ Upstream commit d0930bb8f46b8fb4a7d429c0bf1c91b3ed00a7cf ]
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
Fixes: ac0d6b926e74 ("block: Reduce the amount of memory required per request queue") Signed-off-by: Bart Van Assche bvanassche@acm.org Reviewed-by: Ming Lei ming.lei@redhat.com Cc: Keith Busch kbusch@kernel.org Cc: Johannes Thumshirn jth@kernel.org Cc: Hannes Reinecke hare@suse.com Cc: Christoph Hellwig hch@infradead.org Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- block/blk-mq.c | 1 - 1 file changed, 1 deletion(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c index 329df7986bf60..51ff4852d34bc 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2766,7 +2766,6 @@ 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; }