On 11/19/2014 03:44 AM, Sasha Levin wrote: > On 11/18/2014 07:09 PM, Andrey Ryabinin wrote: >> Yes with CONFIG_KASAN_INLINE you will get GPF instead of kasan report. >> For userspaces addresses we don't have shadow memory. In outline case >> I just check address itself before checking shadow. In inline case compiler >> just checks shadow, so there is no way to avoid GPF. >> >> To be able to print report instead of GPF, I need to treat GPFs in a special >> way if inline instrumentation was enabled, but it's not done yet. > > I went ahead and tested it with the test module, which worked perfectly. No > more complaints here... > >>>> I remembered that one of the biggest changes in kasan was the introduction of >>>> inline instrumentation, so I went ahead to disable it and see if it helps. But >>>> the only result of that was having the boot process hang pretty early: >>>> >>>> [...] >>>> [ 0.000000] IOAPIC[0]: apic_id 21, version 17, address 0xfec00000, GSI 0-23 >>>> [ 0.000000] Processors: 20 >>>> [ 0.000000] smpboot: Allowing 24 CPUs, 4 hotplug CPUs >>>> [ 0.000000] e820: [mem 0xd0000000-0xffffffff] available for PCI devices >>>> [ 0.000000] Booting paravirtualized kernel on KVM >>>> [ 0.000000] setup_percpu: NR_CPUS:8192 nr_cpumask_bits:24 nr_cpu_ids:24 nr_node_ids:1 >>>> [ 0.000000] PERCPU: Embedded 491 pages/cpu @ffff8808dce00000 s1971864 r8192 d31080 u2097152 >>>> *HANG* >>>> >> This hang happens only with your error patch above or even without it? > > It happens even without the patch. > I took your config from "Replace _PAGE_NUMA with PAGE_NONE protections" thread. I've noticed that you have both KASAN and UBSAN enabled. I didn't try them together, though it could work with patch bellow. But it should hang much earlier then you see, without this patch. ------------------------------------------------------ From: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx> Subject: [PATCH] kasan: don't use ubsan's instrumentation for kasan internals kasan do unaligned access for checking shadow memory faster. If ubsan is also enabled this will lead to unbound recursion: __asan_load* -> __ubsan_handle_type_mismatch -> __asan_load* -> ... Disable ubsan's instrumentation for kasan.c to avoid that. Signed-off-by: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx> --- mm/kasan/Makefile | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile index ef2d313..2b53073 100644 --- a/mm/kasan/Makefile +++ b/mm/kasan/Makefile @@ -1,4 +1,5 @@ KASAN_SANITIZE := n +UBSAN_SANITIZE := n # Function splitter causes unnecessary splits in __asan_load1/__asan_store1 # see: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63533 -- 2.1.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>