On Tue, Mar 09, 2021 at 07:18:32PM +0100, Vlastimil Babka wrote: > On 3/9/21 7:14 PM, Georgi Djakov wrote: > > Hi Vlastimil, > > > > Thanks for the comment! > > > > On 3/9/21 17:09, Vlastimil Babka wrote: > >> On 3/9/21 2:47 PM, Georgi Djakov wrote: > >>> Being able to stop the system immediately when a memory corruption > >>> is detected is crucial to finding the source of it. This is very > >>> useful when the memory can be inspected with kdump or other tools. > >> > >> Is this in some testing scenarios where you would also use e.g. panic_on_warn? > >> We could hook to that. If not, we could introduce a new > >> panic_on_memory_corruption that would apply also for debug_pagealloc and whatnot? > > > > I would prefer that we not tie it with panic_on_warn - there might be lots of > > new code in multiple subsystems, so hitting some WARNing while testing is not > > something unexpected. > > > > Introducing an additional panic_on_memory_corruption would work, but i noticed > > that we already have slub_debug and thought to re-use that. But indeed, аdding > > an option to panic in for example bad_page() sounds also useful, if that's what > > you suggest. > > Yes, that would be another example. > Also CCing Kees for input, as besides the "kdump ASAP for debugging" case, I can > imagine security hardening folks could be interested in the "somebody might have > just failed to pwn the kernel, better panic than let them continue" angle. But > I'm naive wrt security, so it might be a stupid idea :) I've really wanted such things, but Linus has been pretty adamant about not wanting to provide new "panic" paths (or even BUG usage[1]). It seems that panic_on_warn remains the way to get this behavior, with the understanding that WARN should only be produced on expected-to-be-impossible situations[1]. Hitting a WARN while testing should result in either finding and fixing a real bug, or removing the WARN in favor of pr_warn(). :) -Kees [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#bug-and-bug-on -- Kees Cook
