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[2/2] tracing, kasan: Silence Kasan warning in check_stack of stack_tracer

Message ID 20160222152311.954701528@goodmis.org
State Accepted
Commit 6e22c8366416251a3d88ba6c92d13d595089f0ed
Headers show

Commit Message

Steven Rostedt Feb. 22, 2016, 3:22 p.m. UTC 
From: Yang Shi <yang.shi@linaro.org>


When enabling stack trace via "echo 1 > /proc/sys/kernel/stack_tracer_enabled",
the below KASAN warning is triggered:

BUG: KASAN: stack-out-of-bounds in check_stack+0x344/0x848 at addr ffffffc0689ebab8
Read of size 8 by task ksoftirqd/4/29
page:ffffffbdc3a27ac0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x0()
page dumped because: kasan: bad access detected
CPU: 4 PID: 29 Comm: ksoftirqd/4 Not tainted 4.5.0-rc1 #129
Hardware name: Freescale Layerscape 2085a RDB Board (DT)
Call trace:
[<ffffffc000091300>] dump_backtrace+0x0/0x3a0
[<ffffffc0000916c4>] show_stack+0x24/0x30
[<ffffffc0009bbd78>] dump_stack+0xd8/0x168
[<ffffffc000420bb0>] kasan_report_error+0x6a0/0x920
[<ffffffc000421688>] kasan_report+0x70/0xb8
[<ffffffc00041f7f0>] __asan_load8+0x60/0x78
[<ffffffc0002e05c4>] check_stack+0x344/0x848
[<ffffffc0002e0c8c>] stack_trace_call+0x1c4/0x370
[<ffffffc0002af558>] ftrace_ops_no_ops+0x2c0/0x590
[<ffffffc00009f25c>] ftrace_graph_call+0x0/0x14
[<ffffffc0000881bc>] fpsimd_thread_switch+0x24/0x1e8
[<ffffffc000089864>] __switch_to+0x34/0x218
[<ffffffc0011e089c>] __schedule+0x3ac/0x15b8
[<ffffffc0011e1f6c>] schedule+0x5c/0x178
[<ffffffc0001632a8>] smpboot_thread_fn+0x350/0x960
[<ffffffc00015b518>] kthread+0x1d8/0x2b0
[<ffffffc0000874d0>] ret_from_fork+0x10/0x40
Memory state around the buggy address:
 ffffffc0689eb980: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 f4 f4 f4
 ffffffc0689eba00: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
>ffffffc0689eba80: 00 00 f1 f1 f1 f1 00 f4 f4 f4 f3 f3 f3 f3 00 00

                                        ^
 ffffffc0689ebb00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffc0689ebb80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

The stacker tracer traverses the whole kernel stack when saving the max stack
trace. It may touch the stack red zones to cause the warning. So, just disable
the instrumentation to silence the warning.

Link: http://lkml.kernel.org/r/1455309960-18930-1-git-send-email-yang.shi@linaro.org

Signed-off-by: Yang Shi <yang.shi@linaro.org>

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

---
 kernel/trace/trace_stack.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

-- 
2.6.4
diff mbox

Patch

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 202df6cffcca..2a1abbaca10e 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -156,7 +156,11 @@  check_stack(unsigned long ip, unsigned long *stack)
 		for (; p < top && i < stack_trace_max.nr_entries; p++) {
 			if (stack_dump_trace[i] == ULONG_MAX)
 				break;
-			if (*p == stack_dump_trace[i]) {
+			/*
+			 * The READ_ONCE_NOCHECK is used to let KASAN know that
+			 * this is not a stack-out-of-bounds error.
+			 */
+			if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) {
 				stack_dump_trace[x] = stack_dump_trace[i++];
 				this_size = stack_trace_index[x++] =
 					(top - p) * sizeof(unsigned long);