Re: [PATCH] block: blk_init_allocated_queue() set q->fq as NULL in the fail case

On 7/30/18 12:11 AM, xiao jin wrote:

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().

Applied, thanks.