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

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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@xxxxxxxxxxxxxxx
Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
---
  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




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