Re: usercopy whitelist woe in scsi_sense_cache

[Kees Cook]

On Mon, Apr 16, 2018 at 8:12 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> With a hardware watchpoint, I've isolated the corruption to here:
>
> bfq_dispatch_request+0x2be/0x1610:
> __bfq_dispatch_request at block/bfq-iosched.c:3902
> 3900            if (rq) {
> 3901    inc_in_driver_start_rq:
> 3902                    bfqd->rq_in_driver++;
> 3903    start_rq:
> 3904                    rq->rq_flags |= RQF_STARTED;
> 3905            }

FWIW, the stacktrace here (removing the ? lines) is:

[   34.311980] RIP: 0010:bfq_dispatch_request+0x2be/0x1610
[   34.452491]  blk_mq_do_dispatch_sched+0x1d9/0x260
[   34.454561]  blk_mq_sched_dispatch_requests+0x3da/0x4b0
[   34.458789]  __blk_mq_run_hw_queue+0xae/0x130
[   34.460001]  __blk_mq_delay_run_hw_queue+0x192/0x280
[   34.460823]  blk_mq_run_hw_queue+0x10b/0x1b0
[   34.463240]  blk_mq_sched_insert_request+0x3bd/0x4d0
[   34.467342]  blk_execute_rq+0xcf/0x140
[   34.468483]  sg_io+0x2f7/0x730

Can anyone tell me more about the memory allocation layout of the
various variables here? It looks like struct request is a header in
front of struct scsi_request? How do struct elevator_queue, struct
blk_mq_ctx, and struct blk_mq_hw_ctx overlap these?

Regardless, I'll check for elevator data changing too...

-Kees

-- 
Kees Cook
Pixel Security