lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Thu, 21 Jul 2016 23:08:40 -0400 From: Brian Gerst <brgerst@...il.com> To: Josh Poimboeuf <jpoimboe@...hat.com> Cc: Andy Lutomirski <luto@...capital.net>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>, "H . Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Steven Rostedt <rostedt@...dmis.org>, Kees Cook <keescook@...omium.org>, Peter Zijlstra <peterz@...radead.org>, Frederic Weisbecker <fweisbec@...il.com>, Byungchul Park <byungchul.park@....com> Subject: Re: [PATCH 03/19] x86/dumpstack: remove unnecessary stack pointer arguments On Thu, Jul 21, 2016 at 9:41 PM, Josh Poimboeuf <jpoimboe@...hat.com> wrote: > On Thu, Jul 21, 2016 at 02:56:52PM -0700, Andy Lutomirski wrote: >> On Thu, Jul 21, 2016 at 2:21 PM, Josh Poimboeuf <jpoimboe@...hat.com> wrote: >> > When calling show_stack_log_lvl() or dump_trace() with a regs argument, >> > providing a stack pointer or frame pointer is redundant. >> > >> >> > diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c >> > index 358fe1c..c533b8b 100644 >> > --- a/arch/x86/kernel/dumpstack_32.c >> > +++ b/arch/x86/kernel/dumpstack_32.c >> > @@ -122,7 +122,7 @@ void show_regs(struct pt_regs *regs) >> > u8 *ip; >> > >> > pr_emerg("Stack:\n"); >> > - show_stack_log_lvl(NULL, regs, ®s->sp, 0, KERN_EMERG); >> > + show_stack_log_lvl(NULL, regs, NULL, 0, KERN_EMERG); >> >> This is weird -- note the &. You're at some risk of exposing a bug in >> x86_32's kernel_stack_pointer() function, which is a mess. (I don't >> see why it's written the way it is -- the actual return stack pointer >> given a pt_regs is quite well defined -- if regs->cs & 3 != 0, then >> it's regs->sp, else it's ®s->sp.) >> >> That being said, this isn't a big deal, so: >> >> Reviewed-by: Andy Lutomirski <luto@...nel.org> >> >> If you want to make this all a bit more reliably on x86_32, you could >> fix kernel_stack_pointer(). > > Ok. The whole '®s->sp' thing threw me for a loop. I have no idea > what kernel_stack_pointer() is trying to do. I just assumed it was > correct. I'll take a look at it and try to fix it in another patch. On 32-bit, when an interrupt doesn't change CPL, SS:ESP is not pushed. So, effectively, the old stack pointer is ®s->sp. -- Brian Gerst
Powered by blists - more mailing lists