On 29.09.2021 23:06, Kees Cook wrote: > On Wed, Sep 29, 2021 at 12:03:36PM -0700, Dave Hansen wrote: >> On 9/29/21 11:58 AM, Alexander Popov wrote: >>> --- a/kernel/panic.c >>> +++ b/kernel/panic.c >>> @@ -53,6 +53,7 @@ static int pause_on_oops_flag; >>> static DEFINE_SPINLOCK(pause_on_oops_lock); >>> bool crash_kexec_post_notifiers; >>> int panic_on_warn __read_mostly; >>> +int pkill_on_warn __read_mostly; > > I like this idea. I can't tell if Linus would tolerate it, though. But I > really have wanted a middle ground like BUG(). Having only WARN() and > panic() is not very friendly. :( Ok, let's see. Kees, could you also share your thoughts on the good questions by Petr Mladek in this thread? >>> unsigned long panic_on_taint; >>> bool panic_on_taint_nousertaint = false; >>> >>> @@ -610,6 +611,9 @@ void __warn(const char *file, int line, void *caller, unsigned taint, >>> >>> print_oops_end_marker(); >>> >>> + if (pkill_on_warn && system_state >= SYSTEM_RUNNING) >>> + do_group_exit(SIGKILL); >>> + >>> /* Just a warning, don't kill lockdep. */ >>> add_taint(taint, LOCKDEP_STILL_OK); >>> } >> >> Doesn't this tie into the warning *printing* code? That's better than >> nothing, for sure. But, if we're doing this for hardening, I think we >> would want to kill anyone provoking a warning, not just the first one >> that triggered *printing* the warning. > > Right, this needs to be moved into the callers of __warn() (i.e. > report_bug(), and warn_slowpath_fmt()), likely with some small > refactoring in report_bug(). Yes, I see now. Thanks, Dave, Peter and Kees. The kernel can hit warning and omit calling __warn() that prints the message. But pkill_on_warn action should be taken each time. As I can understand now, include/asm-generic/bug.h defines three warning implementations: 1. CONFIG_BUG=y and the arch provides __WARN_FLAGS. In that case pkill_on_warn should be checked in report_bug() that you mention. 2. CONFIG_BUG=y and the arch doesn't have __WARN_FLAGS. In that case pkill_on_warn should be checked in warn_slowpath_fmt(). 3. CONFIG_BUG is not set. In that case pkill_on_warn should not be considered. Please, correct me if needed. Best regards, Alexander
