From: Andy Lutomirski <luto@amacapital.net> To: "Mika Penttilä" <mika.penttila@nextfour.com> Cc: Nadav Amit <nadav.amit@gmail.com>, Kees Cook <keescook@chromium.org>, Josh Poimboeuf <jpoimboe@redhat.com>, Borislav Petkov <bp@alien8.de>, "kernel-hardening@lists.openwall.com" <kernel-hardening@lists.openwall.com>, Brian Gerst <brgerst@gmail.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>, Linus Torvalds <torvalds@linux-foundation.org> Subject: Re: [PATCH 12/13] x86/mm/64: Enable vmapped stacks Date: Wed, 15 Jun 2016 22:33:52 -0700 [thread overview] Message-ID: <CALCETrVPMD5KYwqL-1j8hyezJ+GvskeFizfOEh4cUXw0dT3CHg@mail.gmail.com> (raw) In-Reply-To: <57622865.2070701@nextfour.com> On Jun 15, 2016 9:32 PM, "Mika Penttilä" <mika.penttila@nextfour.com> wrote: > > Hi, > > > diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c > > index 5643fd0b1a7d..fbf036ae72ac 100644 > > --- a/arch/x86/mm/tlb.c > > +++ b/arch/x86/mm/tlb.c > > @@ -77,10 +77,25 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, > > unsigned cpu = smp_processor_id(); > > > > if (likely(prev != next)) { > > + if (IS_ENABLED(CONFIG_VMAP_STACK)) { > > + /* > > + * If our current stack is in vmalloc space and isn't > > + * mapped in the new pgd, we'll double-fault. Forcibly > > + * map it. > > + */ > > + unsigned int stack_pgd_index = > > + pgd_index(current_stack_pointer()); > > > stack pointer is still the previous task's, current_stack_pointer() returns that, not > next task's which was intention I guess. Things may happen to work if on same pgd, but at least the > boot cpu init_task_struct is special. This is intentional. When switching processes, we first switch the mm and then switch the task. We need to make sure that the prev stack is mapped in the new mm or we'll double-fault and die after switching the mm which still trying to execute on the old stack. The change to switch_to makes sure that the new stack is mapped. --Andy
WARNING: multiple messages have this Message-ID (diff)
From: Andy Lutomirski <luto@amacapital.net> To: "Mika Penttilä" <mika.penttila@nextfour.com> Cc: Nadav Amit <nadav.amit@gmail.com>, Kees Cook <keescook@chromium.org>, Josh Poimboeuf <jpoimboe@redhat.com>, Borislav Petkov <bp@alien8.de>, "kernel-hardening@lists.openwall.com" <kernel-hardening@lists.openwall.com>, Brian Gerst <brgerst@gmail.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>, Linus Torvalds <torvalds@linux-foundation.org> Subject: [kernel-hardening] Re: [PATCH 12/13] x86/mm/64: Enable vmapped stacks Date: Wed, 15 Jun 2016 22:33:52 -0700 [thread overview] Message-ID: <CALCETrVPMD5KYwqL-1j8hyezJ+GvskeFizfOEh4cUXw0dT3CHg@mail.gmail.com> (raw) In-Reply-To: <57622865.2070701@nextfour.com> On Jun 15, 2016 9:32 PM, "Mika Penttilä" <mika.penttila@nextfour.com> wrote: > > Hi, > > > diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c > > index 5643fd0b1a7d..fbf036ae72ac 100644 > > --- a/arch/x86/mm/tlb.c > > +++ b/arch/x86/mm/tlb.c > > @@ -77,10 +77,25 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, > > unsigned cpu = smp_processor_id(); > > > > if (likely(prev != next)) { > > + if (IS_ENABLED(CONFIG_VMAP_STACK)) { > > + /* > > + * If our current stack is in vmalloc space and isn't > > + * mapped in the new pgd, we'll double-fault. Forcibly > > + * map it. > > + */ > > + unsigned int stack_pgd_index = > > + pgd_index(current_stack_pointer()); > > > stack pointer is still the previous task's, current_stack_pointer() returns that, not > next task's which was intention I guess. Things may happen to work if on same pgd, but at least the > boot cpu init_task_struct is special. This is intentional. When switching processes, we first switch the mm and then switch the task. We need to make sure that the prev stack is mapped in the new mm or we'll double-fault and die after switching the mm which still trying to execute on the old stack. The change to switch_to makes sure that the new stack is mapped. --Andy
next prev parent reply other threads:[~2016-06-16 5:34 UTC|newest] Thread overview: 112+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-06-16 0:28 [PATCH 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski 2016-06-16 0:28 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 0:28 ` [PATCH 01/13] x86/mm/hotplug: Don't remove PGD entries in remove_pagetable() Andy Lutomirski 2016-06-16 0:28 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 0:28 ` Andy Lutomirski 2016-06-16 0:28 ` [PATCH 02/13] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated Andy Lutomirski 2016-06-16 0:28 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 0:28 ` [PATCH 03/13] x86/cpa: Warn if kernel_unmap_pages_in_pgd is used inappropriately Andy Lutomirski 2016-06-16 0:28 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 0:28 ` [PATCH 04/13] mm: Track NR_KERNEL_STACK in pages instead of number of stacks Andy Lutomirski 2016-06-16 0:28 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 0:28 ` Andy Lutomirski 2016-06-16 11:10 ` Vladimir Davydov 2016-06-16 11:10 ` [kernel-hardening] " Vladimir Davydov 2016-06-16 11:10 ` Vladimir Davydov 2016-06-16 17:21 ` Andy Lutomirski 2016-06-16 17:21 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 17:21 ` Andy Lutomirski 2016-06-16 19:20 ` Andy Lutomirski 2016-06-16 19:20 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 19:20 ` Andy Lutomirski 2016-06-16 15:33 ` Josh Poimboeuf 2016-06-16 15:33 ` [kernel-hardening] " Josh Poimboeuf 2016-06-16 15:33 ` Josh Poimboeuf 2016-06-16 17:39 ` Andy Lutomirski 2016-06-16 17:39 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 17:39 ` Andy Lutomirski 2016-06-16 19:39 ` Josh Poimboeuf 2016-06-16 19:39 ` [kernel-hardening] " Josh Poimboeuf 2016-06-16 19:39 ` Josh Poimboeuf 2016-06-16 0:28 ` [PATCH 05/13] mm: Move memcg stack accounting to account_kernel_stack Andy Lutomirski 2016-06-16 0:28 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 0:28 ` Andy Lutomirski 2016-06-16 0:28 ` [PATCH 06/13] fork: Add generic vmalloced stack support Andy Lutomirski 2016-06-16 0:28 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 17:25 ` Kees Cook 2016-06-16 17:25 ` [kernel-hardening] " Kees Cook 2016-06-16 17:37 ` Andy Lutomirski 2016-06-16 17:37 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 0:28 ` [PATCH 07/13] x86/die: Don't try to recover from an OOPS on a non-default stack Andy Lutomirski 2016-06-16 0:28 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 0:28 ` [PATCH 08/13] x86/dumpstack: When OOPSing, rewind the stack before do_exit Andy Lutomirski 2016-06-16 0:28 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 17:50 ` Josh Poimboeuf 2016-06-16 17:50 ` [kernel-hardening] " Josh Poimboeuf 2016-06-16 17:57 ` Andy Lutomirski 2016-06-16 17:57 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 0:28 ` [PATCH 09/13] x86/dumpstack: When dumping stack bytes due to OOPS, start with regs->sp Andy Lutomirski 2016-06-16 0:28 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 11:56 ` Borislav Petkov 2016-06-16 11:56 ` [kernel-hardening] " Borislav Petkov 2016-07-08 12:07 ` [tip:x86/debug] x86/dumpstack: Honor supplied @regs arg tip-bot for Andy Lutomirski 2016-06-16 0:28 ` [PATCH 10/13] x86/dumpstack: Try harder to get a call trace on stack overflow Andy Lutomirski 2016-06-16 0:28 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 18:16 ` Josh Poimboeuf 2016-06-16 18:16 ` [kernel-hardening] " Josh Poimboeuf 2016-06-16 18:22 ` Andy Lutomirski 2016-06-16 18:22 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 18:33 ` Josh Poimboeuf 2016-06-16 18:33 ` [kernel-hardening] " Josh Poimboeuf 2016-06-16 18:37 ` Andy Lutomirski 2016-06-16 18:37 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 18:54 ` Josh Poimboeuf 2016-06-16 18:54 ` [kernel-hardening] " Josh Poimboeuf 2016-06-16 0:28 ` [PATCH 11/13] x86/dumpstack/64: Handle faults when printing the "Stack:" part of an OOPS Andy Lutomirski 2016-06-16 0:28 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 0:28 ` [PATCH 12/13] x86/mm/64: Enable vmapped stacks Andy Lutomirski 2016-06-16 0:28 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 4:17 ` Mika Penttilä 2016-06-16 4:17 ` [kernel-hardening] " Mika Penttilä 2016-06-16 5:33 ` Andy Lutomirski [this message] 2016-06-16 5:33 ` Andy Lutomirski 2016-06-16 13:11 ` Rik van Riel 2016-06-16 0:28 ` [PATCH 13/13] x86/mm: Improve stack-overflow #PF handling Andy Lutomirski 2016-06-16 0:28 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 6:05 ` [PATCH 00/13] Virtually mapped stacks with guard pages (x86, core) Heiko Carstens 2016-06-16 6:05 ` [kernel-hardening] " Heiko Carstens 2016-06-16 17:50 ` Andy Lutomirski 2016-06-16 17:50 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 18:14 ` Andy Lutomirski 2016-06-16 18:14 ` [kernel-hardening] " Andy Lutomirski 2016-06-16 21:27 ` Andy Lutomirski 2016-06-16 21:27 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 3:58 ` Andy Lutomirski 2016-06-17 3:58 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 7:27 ` Heiko Carstens 2016-06-17 7:27 ` [kernel-hardening] " Heiko Carstens 2016-06-17 17:38 ` Andy Lutomirski 2016-06-17 17:38 ` [kernel-hardening] " Andy Lutomirski 2016-06-20 5:58 ` Heiko Carstens 2016-06-20 5:58 ` [kernel-hardening] " Heiko Carstens 2016-06-20 6:01 ` Andy Lutomirski 2016-06-20 6:01 ` [kernel-hardening] " Andy Lutomirski 2016-06-20 7:07 ` Heiko Carstens 2016-06-20 7:07 ` [kernel-hardening] " Heiko Carstens 2016-06-16 17:24 ` Kees Cook 2016-06-16 17:24 ` [kernel-hardening] " Kees Cook 2016-07-04 22:31 [PATCH -v2 0/3] x86/MSR: Improve unhandled MSR access error message Borislav Petkov 2016-07-04 22:31 ` [PATCH -v2 1/3] x86/dumpstack: Honor supplied @regs arg Borislav Petkov 2016-07-04 22:31 ` [PATCH -v2 2/3] printk: Make the printk*once() variants return a value Borislav Petkov 2016-07-08 12:08 ` [tip:x86/debug] " tip-bot for Borislav Petkov 2016-07-09 2:40 ` Joe Perches 2016-07-09 7:50 ` Borislav Petkov 2016-07-09 17:56 ` Joe Perches 2016-07-10 6:49 ` Borislav Petkov 2016-07-10 8:23 ` Joe Perches 2016-07-10 12:06 ` Borislav Petkov 2016-07-10 12:33 ` Joe Perches 2016-07-04 22:31 ` [PATCH -v2 3/3] x86/dumpstack: Add show_stack_regs() and use it Borislav Petkov 2016-07-08 12:08 ` [tip:x86/debug] " tip-bot for Borislav Petkov 2016-07-06 12:58 ` [PATCH -v2 0/3] x86/MSR: Improve unhandled MSR access error message Andy Lutomirski 2016-07-06 13:11 ` Borislav Petkov
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