On Thu, Nov 05, 2020 at 10:21:33AM +0100, Marco Elver wrote: > Instead of removing the fault handling portion of the stack trace based > on the fault handler's name, just use struct pt_regs directly. > > Change kfence_handle_page_fault() to take a struct pt_regs, and plumb it > through to kfence_report_error() for out-of-bounds, use-after-free, or > invalid access errors, where pt_regs is used to generate the stack > trace. > > If the kernel is a DEBUG_KERNEL, also show registers for more > information. > > Suggested-by: Mark Rutland <mark.rutland@xxxxxxx> > Signed-off-by: Marco Elver <elver@xxxxxxxxxx> Wow; I wasn't expecting this to be put together so quickly, thanks for doing this! >From a scan, this looks good to me -- just one question below. > diff --git a/include/linux/kfence.h b/include/linux/kfence.h > index ed2d48acdafe..98a97f9d43cd 100644 > --- a/include/linux/kfence.h > +++ b/include/linux/kfence.h > @@ -171,6 +171,7 @@ static __always_inline __must_check bool kfence_free(void *addr) > /** > * kfence_handle_page_fault() - perform page fault handling for KFENCE pages > * @addr: faulting address > + * @regs: current struct pt_regs (can be NULL, but shows full stack trace) > * > * Return: > * * false - address outside KFENCE pool, > @@ -44,8 +44,12 @@ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries > case KFENCE_ERROR_UAF: > case KFENCE_ERROR_OOB: > case KFENCE_ERROR_INVALID: > - is_access_fault = true; > - break; > + /* > + * kfence_handle_page_fault() may be called with pt_regs > + * set to NULL; in that case we'll simply show the full > + * stack trace. > + */ > + return 0; For both the above comments, when/where is kfence_handle_page_fault() called with regs set to NULL? I couldn't spot that in this patch, so unless I mised it I'm guessing that's somewhere outside of the patch context? If this is a case we don't expect to happen, maybe add a WARN_ON_ONCE()? Thanks, Mark.
