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From: Andy Lutomirski <luto@amacapital.net>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>
Subject: Re: [patch V2 28/29] x86/irq/64: Remap the IRQ stack with guard pages
Date: Sun, 7 Apr 2019 02:28:07 -0700	[thread overview]
Message-ID: <50F7A079-11F5-45EA-B378-7527B5920A7C@amacapital.net> (raw)
In-Reply-To: <alpine.DEB.2.21.1904070803200.1840@nanos.tec.linutronix.de>



> On Apr 6, 2019, at 11:08 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> 
>> On Sat, 6 Apr 2019, Andy Lutomirski wrote:
>>> On Fri, Apr 5, 2019 at 8:11 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>>> 
>>> From: Andy Lutomirski <luto@kernel.org>
>>> 
>>> The IRQ stack lives in percpu space, so an IRQ handler that overflows it
>>> will overwrite other data structures.
>>> 
>>> Use vmap() to remap the IRQ stack so that it will have the usual guard
>>> pages that vmap/vmalloc allocations have. With this the kernel will panic
>>> immediately on an IRQ stack overflow.
>> 
>> The 0day bot noticed that this dies with DEBUG_PAGEALLOC on.  This is
>> because the store_stackinfo() function is utter garbage and this patch
>> correctly detects just how broken it is.  The attached patch "fixes"
>> it.  (It also contains a reliability improvement that should probably
>> get folded in, but is otherwise unrelated.)
>> 
>> A real fix would remove the generic kstack_end() function entirely
>> along with __HAVE_ARCH_KSTACK_END and would optionally replace
>> store_stackinfo() with something useful.  Josh, do we have a generic
>> API to do a little stack walk like this?  Otherwise, I don't think it
>> would be the end of the world to just remove the offending code.
> 
> Yes, I found the same yesterday before heading out. It's already broken
> with the percpu stack because there is no guarantee that the per cpu stack
> is thread size aligned. It's guaranteed to be page aligned not more.
> 
> I'm all for removing that nonsense, but the real question is whether there
> is more code which assumes THREAD_SIZE aligned stacks aside of the thread
> stack itself.
> 
> 

Well, any code like this is already busted, since the stacks alignment doesn’t really change with these patches applied.

  reply	other threads:[~2019-04-07  9:28 UTC|newest]

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-05 15:06 [patch V2 00/29] x86: Add guard pages to exception and interrupt stacks Thomas Gleixner
2019-04-05 15:06 ` [patch V2 01/29] x86/irq/64: Limit IST stack overflow check to #DB stack Thomas Gleixner
2019-04-05 15:07 ` [patch V2 02/29] x86/dumpstack: Fix off-by-one errors in stack identification Thomas Gleixner
2019-04-05 15:44   ` Sean Christopherson
2019-04-05 15:07 ` [patch V2 03/29] x86/irq/64: Remove a hardcoded irq_stack_union access Thomas Gleixner
2019-04-05 16:37   ` Sean Christopherson
2019-04-05 16:38     ` Sean Christopherson
2019-04-05 17:18     ` Josh Poimboeuf
2019-04-05 17:47       ` Thomas Gleixner
2019-04-05 15:07 ` [patch V2 04/29] x86/irq/64: Sanitize the top/bottom confusion Thomas Gleixner
2019-04-05 16:54   ` Sean Christopherson
2019-04-05 15:07 ` [patch V2 05/29] x86/idt: Remove unused macro SISTG Thomas Gleixner
2019-04-05 15:07 ` [patch V2 06/29] x86/exceptions: Remove unused stack defines on 32bit Thomas Gleixner
2019-04-05 15:07 ` [patch V2 07/29] x86/exceptions: Make IST index zero based Thomas Gleixner
2019-04-05 18:59   ` Sean Christopherson
2019-04-05 15:07 ` [patch V2 08/29] x86/cpu_entry_area: Cleanup setup functions Thomas Gleixner
2019-04-05 19:25   ` Sean Christopherson
2019-04-05 15:07 ` [patch V2 09/29] x86/exceptions: Add structs for exception stacks Thomas Gleixner
2019-04-05 20:48   ` Sean Christopherson
2019-04-05 20:50     ` Sean Christopherson
2019-04-05 21:00     ` Thomas Gleixner
2019-04-05 15:07 ` [patch V2 10/29] x86/cpu_entry_area: Prepare for IST guard pages Thomas Gleixner
2019-04-05 15:07 ` [patch V2 11/29] x86/cpu_entry_area: Provide exception stack accessor Thomas Gleixner
2019-04-05 15:07 ` [patch V2 12/29] x86/traps: Use cpu_entry_area instead of orig_ist Thomas Gleixner
2019-04-05 15:07 ` [patch V2 13/29] x86/irq/64: Use cpu entry area " Thomas Gleixner
2019-04-05 15:07 ` [patch V2 14/29] x86/dumpstack/64: Use cpu_entry_area " Thomas Gleixner
2019-04-05 15:07 ` [patch V2 15/29] x86/cpu: Prepare TSS.IST setup for guard pages Thomas Gleixner
2019-04-05 15:07 ` [patch V2 16/29] x86/cpu: Remove orig_ist array Thomas Gleixner
2019-04-05 15:07 ` [patch V2 17/29] x86/exceptions: Disconnect IST index and stack order Thomas Gleixner
2019-04-05 21:57   ` Josh Poimboeuf
2019-04-05 22:00     ` Thomas Gleixner
2019-04-05 15:07 ` [patch V2 18/29] x86/exceptions: Enable IST guard pages Thomas Gleixner
2019-04-05 15:07 ` [patch V2 19/29] x86/exceptions: Split debug IST stack Thomas Gleixner
2019-04-05 20:55   ` Sean Christopherson
2019-04-05 21:01     ` Thomas Gleixner
2019-04-05 15:07 ` [patch V2 20/29] x86/dumpstack/64: Speedup in_exception_stack() Thomas Gleixner
2019-04-05 21:55   ` Josh Poimboeuf
2019-04-05 21:56     ` Thomas Gleixner
2019-04-05 15:07 ` [patch V2 21/29] x86/irq/32: Define IRQ_STACK_SIZE Thomas Gleixner
2019-04-05 15:07 ` [patch V2 22/29] x86/irq/32: Make irq stack a character array Thomas Gleixner
2019-04-05 15:07 ` [patch V2 23/29] x86/irq/32: Rename hard/softirq_stack to hard/softirq_stack_ptr Thomas Gleixner
2019-04-05 15:07 ` [patch V2 24/29] x86/irq/64: Rename irq_stack_ptr to hardirq_stack_ptr Thomas Gleixner
2019-04-05 15:07 ` [patch V2 25/29] x86/irq/32: Invoke irq_ctx_init() from init_IRQ() Thomas Gleixner
2019-04-05 15:27   ` Juergen Gross
2019-04-05 15:07 ` [patch V2 26/29] x86/irq/32: Handle irq stack allocation failure proper Thomas Gleixner
2019-04-05 15:07 ` [patch V2 27/29] x86/irq/64: Split the IRQ stack into its own pages Thomas Gleixner
2019-04-05 15:07 ` [patch V2 28/29] x86/irq/64: Remap the IRQ stack with guard pages Thomas Gleixner
2019-04-07  4:56   ` Andy Lutomirski
2019-04-07  6:08     ` Thomas Gleixner
2019-04-07  9:28       ` Andy Lutomirski [this message]
2019-04-07  9:34         ` Thomas Gleixner
2019-04-07 14:03           ` Andy Lutomirski
2019-04-07 22:44     ` Thomas Gleixner
2019-04-08  2:23       ` Andy Lutomirski
2019-04-08  6:46         ` Thomas Gleixner
2019-04-08 16:18           ` Andy Lutomirski
2019-04-08 16:36             ` Josh Poimboeuf
2019-04-08 16:44             ` Thomas Gleixner
2019-04-08 18:19               ` Thomas Gleixner
2019-04-05 15:07 ` [patch V2 29/29] x86/irq/64: Remove stack overflow debug code Thomas Gleixner

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