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    SubjectRe: [v2 PATCH] trace, kasan: silence Kasan warning in check_stack
    On Fri, 12 Feb 2016 12:46:00 -0800
    Yang Shi <yang.shi@linaro.org> wrote:

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

    Applied, thanks!

    -- Steve

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