[PATCH] coresight: tmc-etf: Fix global-out-of-bounds in tmc_update_etf_buffer()

[Suzuki K Poulose]

On 05/05/2021 10:34, Sai Prakash Ranjan wrote:
> commit 6f755e85c332 ("coresight: Add helper for inserting synchronization
> packets") removed trailing '\0' from barrier_pkt array and updated the
> call sites like etb_update_buffer() to have proper checks for barrier_pkt
> size before read but missed updating tmc_update_etf_buffer() which still
> reads barrier_pkt past the array size resulting in KASAN out-of-bounds
> bug. Fix this by adding a check for barrier_pkt size before accessing
> like it is done in etb_update_buffer().
> 
>   BUG: KASAN: global-out-of-bounds in tmc_update_etf_buffer+0x4b8/0x698
>   Read of size 4 at addr ffffffd05b7d1030 by task perf/2629
> 
>   Call trace:
>    dump_backtrace+0x0/0x27c
>    show_stack+0x20/0x2c
>    dump_stack+0x11c/0x188
>    print_address_description+0x3c/0x4a4
>    __kasan_report+0x140/0x164
>    kasan_report+0x10/0x18
>    __asan_report_load4_noabort+0x1c/0x24
>    tmc_update_etf_buffer+0x4b8/0x698
>    etm_event_stop+0x248/0x2d8
>    etm_event_del+0x20/0x2c
>    event_sched_out+0x214/0x6f0
>    group_sched_out+0xd0/0x270
>    ctx_sched_out+0x2ec/0x518
>    __perf_event_task_sched_out+0x4fc/0xe6c
>    __schedule+0x1094/0x16a0
>    preempt_schedule_irq+0x88/0x170
>    arm64_preempt_schedule_irq+0xf0/0x18c
>    el1_irq+0xe8/0x180
>    perf_event_exec+0x4d8/0x56c
>    setup_new_exec+0x204/0x400
>    load_elf_binary+0x72c/0x18c0
>    search_binary_handler+0x13c/0x420
>    load_script+0x500/0x6c4
>    search_binary_handler+0x13c/0x420
>    exec_binprm+0x118/0x654
>    __do_execve_file+0x77c/0xba4
>    __arm64_compat_sys_execve+0x98/0xac
>    el0_svc_common+0x1f8/0x5e0
>    el0_svc_compat_handler+0x84/0xb0
>    el0_svc_compat+0x10/0x50
> 
>   The buggy address belongs to the variable:
>    barrier_pkt+0x10/0x40
> 
>   Memory state around the buggy address:
>    ffffffd05b7d0f00: fa fa fa fa 04 fa fa fa fa fa fa fa 00 00 00 00
>    ffffffd05b7d0f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>   >ffffffd05b7d1000: 00 00 00 00 00 00 fa fa fa fa fa fa 00 00 00 03
>                                        ^
>    ffffffd05b7d1080: fa fa fa fa 00 02 fa fa fa fa fa fa 03 fa fa fa
>    ffffffd05b7d1100: fa fa fa fa 00 00 00 00 05 fa fa fa fa fa fa fa
>   ==================================================================
> 
> Fixes: 6f755e85c332 ("coresight: Add helper for inserting synchronization packets")
> Cc: stable at vger.kernel.org
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan at codeaurora.org>
> ---
>   drivers/hwtracing/coresight/coresight-tmc-etf.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> index 45b85edfc690..cd0fb7bfba68 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> @@ -530,7 +530,7 @@ static unsigned long tmc_update_etf_buffer(struct coresight_device *csdev,
>   		buf_ptr = buf->data_pages[cur] + offset;
>   		*buf_ptr = readl_relaxed(drvdata->base + TMC_RRD);
>   
> -		if (lost && *barrier) {
> +		if (lost && i < CORESIGHT_BARRIER_PKT_SIZE) {
>   			*buf_ptr = *barrier;
>   			barrier++;
>   		}
> 

Thanks for the fix. I will queue this one after rc1

Thanks
Suzuki