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From: Dave Hansen <dave.hansen@intel.com>
To: Dave Martin <Dave.Martin@arm.com>
Cc: "H.J. Lu" <hjl.tools@gmail.com>,
	"Chang S. Bae" <chang.seok.bae@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@suse.de>,
	Andy Lutomirski <luto@kernel.org>,
	the arch/x86 maintainers <x86@kernel.org>,
	Len Brown <len.brown@intel.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Tony Luck <tony.luck@intel.com>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	GNU C Library <libc-alpha@sourceware.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 0/4] x86: Improve Minimum Alternate Stack Size
Date: Tue, 6 Oct 2020 11:30:42 -0700	[thread overview]
Message-ID: <3545e3f3-a716-5e82-bd24-450eb74b4563@intel.com> (raw)
In-Reply-To: <20201006170020.GB6642@arm.com>

On 10/6/20 10:00 AM, Dave Martin wrote:
> On Tue, Oct 06, 2020 at 08:33:47AM -0700, Dave Hansen wrote:
>> On 10/6/20 8:25 AM, Dave Martin wrote:
>>> Or are people reporting real stack overruns on x86 today?
>> We have real overruns.  We have ~2800 bytes of XSAVE (regisiter) state
>> mostly from AVX-512, and a 2048 byte MINSIGSTKSZ.
> Right.  Out of interest, do you believe that's a direct consequence of
> the larger kernel-generated signal frame, or does the expansion of
> userspace stack frames play a role too?

The kernel-generated signal frame is entirely responsible for the ~2800
bytes that I'm talking about.

I'm sure there are some systems where userspace plays a role, but those
are much less of a worry at the moment, since the kernel-induced
overflows mean an instant crash that userspace has no recourse for.

  parent reply	other threads:[~2020-10-06 18:31 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-29 20:57 [RFC PATCH 0/4] x86: Improve Minimum Alternate Stack Size Chang S. Bae
2020-09-29 20:57 ` [RFC PATCH 1/4] x86/signal: Introduce helpers to get the maximum signal frame size Chang S. Bae
2020-10-05 13:42   ` Dave Martin
2020-10-06 17:45     ` Bae, Chang Seok
2020-10-07 10:05       ` Dave Martin
2020-10-08 22:43         ` Bae, Chang Seok
2020-10-12 13:26           ` Dave Martin
2020-09-29 20:57 ` [RFC PATCH 2/4] x86/elf: Support a new ELF aux vector AT_MINSIGSTKSZ Chang S. Bae
2020-09-29 20:57 ` [RFC PATCH 3/4] x86/signal: Prevent an alternate stack overflow before a signal delivery Chang S. Bae
2020-09-29 20:57 ` [RFC PATCH 4/4] selftest/x86/signal: Include test cases for validating sigaltstack Chang S. Bae
2020-10-05 13:45 ` [RFC PATCH 0/4] x86: Improve Minimum Alternate Stack Size Dave Martin
2020-10-05 21:17   ` H.J. Lu
2020-10-06  9:25     ` Dave Martin
2020-10-06 12:12       ` H.J. Lu
2020-10-06 15:18         ` H.J. Lu
2020-10-06 15:43           ` Dave Martin
2020-10-06 16:52             ` H.J. Lu
2020-10-06 15:25         ` Dave Martin
2020-10-06 15:33           ` Dave Hansen
2020-10-06 17:00             ` Dave Martin
2020-10-06 18:21               ` Florian Weimer
2020-10-07 10:19                 ` Dave Martin
2020-10-06 18:30               ` Dave Hansen [this message]
2020-10-07 10:20                 ` Dave Martin
2020-10-06 15:34           ` H.J. Lu
2020-10-06 16:55             ` Dave Martin
2020-10-06 17:44               ` H.J. Lu
2020-10-07 10:47                 ` Dave Martin
2020-10-07 13:30                   ` H.J. Lu
2020-10-07 15:45                     ` Dave Martin
2020-10-07 17:43                       ` H.J. Lu

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