From: "Bae, Chang Seok" <chang.seok.bae@intel.com>
To: Borislav Petkov <bp@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
"mingo@kernel.org" <mingo@kernel.org>,
"luto@kernel.org" <luto@kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"Brown, Len" <len.brown@intel.com>,
"Hansen, Dave" <dave.hansen@intel.com>,
"hjl.tools@gmail.com" <hjl.tools@gmail.com>,
"Dave.Martin@arm.com" <Dave.Martin@arm.com>,
"jannh@google.com" <jannh@google.com>,
"mpe@ellerman.id.au" <mpe@ellerman.id.au>,
"carlos@redhat.com" <carlos@redhat.com>,
"Luck, Tony" <tony.luck@intel.com>,
"Shankar, Ravi V" <ravi.v.shankar@intel.com>,
"libc-alpha@sourceware.org" <libc-alpha@sourceware.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v7 5/6] x86/signal: Detect and prevent an alternate signal stack overflow
Date: Tue, 16 Mar 2021 18:26:46 +0000 [thread overview]
Message-ID: <16A53D65-2460-49B3-892B-81EF8D7B12B9@intel.com> (raw)
In-Reply-To: <20210316115248.GB18822@zn.tnic>
On Mar 16, 2021, at 04:52, Borislav Petkov <bp@suse.de> wrote:
> On Mon, Mar 15, 2021 at 11:52:14PM -0700, Chang S. Bae wrote:
>> @@ -272,7 +275,8 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
>> * If we are on the alternate signal stack and would overflow it, don't.
>> * Return an always-bogus address instead so we will die with SIGSEGV.
>> */
>> - if (onsigstack && !likely(on_sig_stack(sp)))
>> + if (onsigstack && unlikely(sp <= current->sas_ss_sp ||
>> + sp - current->sas_ss_sp > current->sas_ss_size))
>> return (void __user *)-1L;
>
> So clearly I'm missing something because trying to trigger the test case
> in the bugzilla:
>
> https://bugzilla.kernel.org/show_bug.cgi?id=153531
>
> on current tip/master doesn't work. Runs with MY_MINSIGSTKSZ under 2048
> fail with:
>
> tst-minsigstksz-2: sigaltstack: Cannot allocate memory
>
> and above 2048 don't overwrite bytes below the stack.
>
> So something else is missing. How did you test this patch?
I suspect the AVX-512 states not enabled there.
When I ran it under a machine without AVX-512 like this, it didn’t show the
overwrite message:
$ cat /proc/cpuinfo | grep -m1 "model name”
model name : Intel(R) Core(TM) i9-10900K CPU @ 3.70GHz
$ sudo dmesg | grep "Enabled xstate”
[ 0.000000] x86/fpu: Enabled xstate features 0x1f, context size is 960
bytes, using ‘compacted’ format.
$ gcc tst-minsigstksz-2.c -DMY_MINSIGSTKSZ=2047
$ ./a.out
a.out: sigaltstack: Cannot allocate memory
$ gcc tst-minsigstksz-2.c -DMY_MINSIGSTKSZ=2048
$ ./a.out
When do it again with AVX-512, it did show the message:
$ cat /proc/cpuinfo | grep -m1 "model name”
model name : Intel(R) Core(TM) i9-7940X CPU @ 3.10GHz
$ sudo dmesg | grep "Enabled xstate”
[ 0.000000] x86/fpu: Enabled xstate features 0xff, context size is 2560
bytes, using 'compacted' format.
$ gcc tst-minsigstksz-2.c -DMY_MINSIGSTKSZ=2048
$ ./a.out
a.out: changed byte 1412 bytes below configured stack
$ gcc tst-minsigstksz-2.c -DMY_MINSIGSTKSZ=3490
$ ./a.out
a.out: changed byte 21 bytes below configured stack
$ gcc tst-minsigstksz-2.c -DMY_MINSIGSTKSZ=3491
$ ./a.out
Also, on the second machine, without this patch:
$ gcc tst-minsigstksz-2.c -DMY_MINSIGSTKSZ=3191
$ ./a.out
a.out: changed byte 319 bytes below configured stack
But with this patch, it gave segfault with a too-small size:
$ gcc tst-minsigstksz-2.c -DMY_MINSIGSTKSZ=3191
$ ./a.out
Segmentation fault (core dumped)
Thanks,
Chang
next prev parent reply other threads:[~2021-03-16 18:28 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-16 6:52 [PATCH v7 0/6] x86: Improve Minimum Alternate Stack Size Chang S. Bae
2021-03-16 6:52 ` [PATCH v7 1/6] uapi: Define the aux vector AT_MINSIGSTKSZ Chang S. Bae
2021-03-16 6:52 ` [PATCH v7 2/6] x86/signal: Introduce helpers to get the maximum signal frame size Chang S. Bae
2021-03-16 6:52 ` [PATCH v7 3/6] x86/elf: Support a new ELF aux vector AT_MINSIGSTKSZ Chang S. Bae
2021-03-16 6:52 ` [PATCH v7 4/6] selftest/sigaltstack: Use the AT_MINSIGSTKSZ aux vector if available Chang S. Bae
2021-03-16 6:52 ` [PATCH v7 5/6] x86/signal: Detect and prevent an alternate signal stack overflow Chang S. Bae
2021-03-16 11:52 ` Borislav Petkov
2021-03-16 18:26 ` Bae, Chang Seok [this message]
2021-03-25 16:20 ` Borislav Petkov
2021-03-25 17:21 ` Bae, Chang Seok
2021-03-25 20:14 ` Florian Weimer
2021-03-25 18:13 ` Andy Lutomirski
2021-03-25 18:54 ` Borislav Petkov
2021-03-25 21:11 ` Bae, Chang Seok
2021-03-25 21:27 ` Borislav Petkov
2021-03-26 4:56 ` Andy Lutomirski
2021-03-26 10:30 ` Borislav Petkov
2021-04-12 22:30 ` Bae, Chang Seok
2021-04-14 10:12 ` Borislav Petkov
2021-04-14 11:30 ` Florian Weimer
2021-04-14 12:06 ` Borislav Petkov
2021-05-03 5:30 ` Florian Weimer
2021-05-03 11:17 ` Borislav Petkov
2021-03-26 4:58 ` Andy Lutomirski
2021-03-16 6:52 ` [PATCH v7 6/6] selftest/x86/signal: Include test cases for validating sigaltstack Chang S. Bae
2021-03-17 10:06 ` [PATCH v7 0/6] x86: Improve Minimum Alternate Stack Size Ingo Molnar
2021-03-17 10:44 ` Ingo Molnar
2021-03-19 18:12 ` Len Brown
2021-03-20 17:32 ` Ingo Molnar
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