On Tue, Nov 15, 2016 at 10:57 AM, Peter Zijlstra <pet...@infradead.org> wrote: > On Tue, Nov 15, 2016 at 12:43:56PM -0500, Vince Weaver wrote: >> >> Running on my haswell machine with the imc/uncore patch applied, the >> perf_fuzzer next tripped over this issue. >> >> [ 202.034495] BAD LUCK: lost 371 message(s) from NMI context! >> [ 202.034496] >> ================================================================== >> [ 202.048327] BUG: KASAN: stack-out-of-bounds in >> unwind_get_return_address+0x35/0x80 at addr ffff8800cff0bd90 >> [ 202.058826] Read of size 8 by task perf_fuzzer/16254 >> [ 202.064186] page:ffffea00033fc2c0 count:1 mapcount:0 mapping: >> (null) index:0x0^Ac >> [ 202.073068] flags: 0x1ffff8000000400(reserved) >> [ 202.077885] page dumped because: kasan: bad access detected >> [ 202.083880] CPU: 4 PID: 16254 Comm: perf_fuzzer Not tainted 4.9.0-rc5+ #5 >> [ 202.091204] Hardware name: LENOVO 10AM000AUS/SHARKBAY, BIOS FBKT72AUS >> 01/26/2014 >> [ 202.099181] ffff8800cff0b1d8^Ac ffffffff816bb796^Ac ffff8800cff0b270^Ac >> ffff8800cff0bd90^Ac >> [ 202.107896] ffff8800cff0b260^Ac ffffffff812fbe95^Ac 00007ffc9d1ab480^Ac >> 0000000000000000^Ac >> [ 202.116638] ffffffff8125117d^Ac 0000000000000092^Ac 0000000000000000^Ac >> ffff8800cff0b7c0^Ac >> [ 202.125339] Call Trace: >> [ 202.127994] <NMI> [<ffffffff816bb796>] dump_stack+0x63/0x8d >> [ 202.134184] [<ffffffff812fbe95>] kasan_report_error+0x495/0x4c0 >> [ 202.140680] [<ffffffff8125117d>] ? perf_output_begin+0x28d/0x4c0 >> [ 202.147228] [<ffffffff812fc319>] kasan_report+0x39/0x40 >> [ 202.152987] [<ffffffff81095ce5>] ? unwind_get_return_address+0x35/0x80 >> [ 202.160094] [<ffffffff812fa8fe>] __asan_load8+0x5e/0x70 >> [ 202.165859] [<ffffffff81095ce5>] unwind_get_return_address+0x35/0x80 > > Josh, any ideas?
I think this is a false positive due to imprecise unwind that hits a stack redzone. We probably need to use READ_ONCE_NOCHECK as in get_wchan.
