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R. Silva" , Arnd Bergmann , Ard Biesheuvel , kasan-dev , Linux-MM , LKML , kernel-hardening@lists.openwall.com, syzkaller Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jan 16, 2020 at 2:24 AM Kees Cook wrote: > > As done in the full WARN() handler, panic_on_warn needs to be cleared > before calling panic() to avoid recursive panics. > > Signed-off-by: Kees Cook > --- > mm/kasan/report.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/mm/kasan/report.c b/mm/kasan/report.c > index 621782100eaa..844554e78893 100644 > --- a/mm/kasan/report.c > +++ b/mm/kasan/report.c > @@ -92,8 +92,16 @@ static void 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) > + if (panic_on_warn) { > + /* > + * This thread may hit another WARN() in the panic path. > + * Resetting this prevents additional WARN() from panicking the > + * system on this thread. Other threads are blocked by the > + * panic_mutex in panic(). I don't understand part about other threads. Other threads are not necessary inside of panic(). And in fact since we reset panic_on_warn, they will not get there even if they should. If I am reading this correctly, once one thread prints a warning and is going to panic, other threads may now print infinite amounts of warning and proceed past them freely. Why is this the behavior we want? > + */ > + panic_on_warn = 0; > panic("panic_on_warn set ...\n"); > + } > kasan_enable_current(); > }