Messages in this thread | | | Subject | Re: [PATCH] kasan: support panic_on_warn | From | Andrey Ryabinin <> | Date | Mon, 17 Oct 2016 11:39:21 +0300 |
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On 10/17/2016 11:18 AM, Dmitry Vyukov wrote: > On Mon, Oct 17, 2016 at 10:13 AM, Andrey Ryabinin > <aryabinin@virtuozzo.com> wrote: >> >> >> On 10/14/2016 08:10 PM, Dmitry Vyukov wrote: >>> If user sets panic_on_warn, he wants kernel to panic if there is >>> anything barely wrong with the kernel. KASAN-detected errors >>> are definitely not less benign than an arbitrary kernel WARNING. >>> >>> Panic after KASAN errors if panic_on_warn is set. >>> >>> We use this for continuous fuzzing where we want kernel to stop >>> and reboot on any error. >>> >>> Signed-off-by: Dmitry Vyukov <dvyukov@google.com> >>> Cc: kasan-dev@googlegroups.com >>> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> >>> Cc: Alexander Potapenko <glider@google.com> >>> Cc: Andrew Morton <akpm@linux-foundation.org> >>> Cc: linux-mm@kvack.org >>> Cc: linux-kernel@vger.kernel.org >>> --- >>> mm/kasan/report.c | 4 ++++ >>> 1 file changed, 4 insertions(+) >>> >>> diff --git a/mm/kasan/report.c b/mm/kasan/report.c >>> index 24c1211..ca0bd48 100644 >>> --- a/mm/kasan/report.c >>> +++ b/mm/kasan/report.c >>> @@ -133,6 +133,10 @@ static void kasan_end_report(unsigned long *flags) >>> pr_err("==================================================================\n"); >>> add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); >>> spin_unlock_irqrestore(&report_lock, *flags); >>> + if (panic_on_warn) { >>> + panic_on_warn = 0; >> >> Why we need to reset panic_on_warn? >> I assume this was copied from __warn(). AFAIU in __warn() this protects from recursion: >> __warn() -> painc() ->__warn() -> panic() -> ... >> which is possible if WARN_ON() triggered in panic(). >> But KASAN is protected from such recursion via kasan_disable_current(). > > But we have recursion into panic via kasan->panic->warning->panic.
We do, like almost every other panic() call in the kernel. But at least it's finite. So, if finite recursion is a problem for panic() it should be fixed in panic(), rather then on every panic() call site.
> >>> + panic("panic_on_warn set ...\n"); >>> + } >>> kasan_enable_current(); >>> }
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