The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 54648cf1ec2d7f4b6a71767799c45676a138ca24 Mon Sep 17 00:00:00 2001

From: xiao jin jin.xiao@intel.com Date: Mon, 30 Jul 2018 14:11:12 +0800 Subject: [PATCH] block: blk_init_allocated_queue() set q->fq as NULL in the fail case

We find the memory use-after-free issue in __blk_drain_queue() on the kernel 4.14. After read the latest kernel 4.18-rc6 we think it has the same problem.

Memory is allocated for q->fq in the blk_init_allocated_queue(). If the elevator init function called with error return, it will run into the fail case to free the q->fq.

Then the __blk_drain_queue() uses the same memory after the free of the q->fq, it will lead to the unpredictable event.

The patch is to set q->fq as NULL in the fail case of blk_init_allocated_queue().

Fixes: commit 7c94e1c157a2 ("block: introduce blk_flush_queue to drive flush machinery") Cc: stable@vger.kernel.org Reviewed-by: Ming Lei ming.lei@redhat.com Reviewed-by: Bart Van Assche bart.vanassche@wdc.com Signed-off-by: xiao jin jin.xiao@intel.com Signed-off-by: Jens Axboe axboe@kernel.dk

diff --git a/block/blk-core.c b/block/blk-core.c index 03a4ea93a5f3..23cd1b7770e7 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1184,6 +1184,7 @@ int blk_init_allocated_queue(struct request_queue *q) q->exit_rq_fn(q, q->fq->flush_rq); out_free_flush_queue: blk_free_flush_queue(q->fq); + q->fq = NULL; return -ENOMEM; } EXPORT_SYMBOL(blk_init_allocated_queue);