From: Borislav Petkov <bp@suse.de>
To: "Bae, Chang Seok" <chang.seok.bae@intel.com>
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: Thu, 25 Mar 2021 17:20:47 +0100 [thread overview]
Message-ID: <20210325162047.GA32296@zn.tnic> (raw)
In-Reply-To: <16A53D65-2460-49B3-892B-81EF8D7B12B9@intel.com>
On Tue, Mar 16, 2021 at 06:26:46PM +0000, Bae, Chang Seok wrote:
> I suspect the AVX-512 states not enabled there.
Ok, I found a machine which has AVX-512:
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x020: 'AVX-512 opmask'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x040: 'AVX-512 Hi256'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x080: 'AVX-512 ZMM_Hi256'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x200: 'Protection Keys User registers'
[ 0.000000] x86/fpu: xstate_offset[2]: 576, xstate_sizes[2]: 256
[ 0.000000] x86/fpu: xstate_offset[5]: 832, xstate_sizes[5]: 64
[ 0.000000] x86/fpu: xstate_offset[6]: 896, xstate_sizes[6]: 512
[ 0.000000] x86/fpu: xstate_offset[7]: 1408, xstate_sizes[7]: 1024
[ 0.000000] x86/fpu: xstate_offset[9]: 2432, xstate_sizes[9]: 8
[ 0.000000] x86/fpu: Enabled xstate features 0x2e7, context size is 2440 bytes, using 'compacted' format.
and applied your patch and added a debug printk, see end of mail.
Then, I ran the test case:
$ gcc tst-minsigstksz-2.c -DMY_MINSIGSTKSZ=3453 -o tst-minsigstksz-2
$ ./tst-minsigstksz-2
tst-minsigstksz-2: changed byte 50 bytes below configured stack
Whoops.
And the debug print said:
[ 5395.252884] signal: get_sigframe: sp: 0x7f54ec39e7b8, sas_ss_sp: 0x7f54ec39e6ce, sas_ss_size 0xd7d
which tells me that, AFAICT, your check whether we have enough alt stack
doesn't seem to work in this case.
Thx.
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index a06cb107c0e8..a7396f7c3832 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -237,7 +237,7 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
unsigned long math_size = 0;
unsigned long sp = regs->sp;
unsigned long buf_fx = 0;
- int onsigstack = on_sig_stack(sp);
+ bool onsigstack = on_sig_stack(sp);
int ret;
/* redzone */
@@ -246,8 +246,11 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
/* This is the X/Open sanctioned signal stack switching. */
if (ka->sa.sa_flags & SA_ONSTACK) {
- if (sas_ss_flags(sp) == 0)
+ if (sas_ss_flags(sp) == 0) {
sp = current->sas_ss_sp + current->sas_ss_size;
+ /* On the alternate signal stack */
+ onsigstack = true;
+ }
} else if (IS_ENABLED(CONFIG_X86_32) &&
!onsigstack &&
regs->ss != __USER_DS &&
@@ -263,11 +266,16 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
sp = align_sigframe(sp - frame_size);
+ if (onsigstack)
+ pr_info("%s: sp: 0x%lx, sas_ss_sp: 0x%lx, sas_ss_size 0x%lx\n",
+ __func__, sp, current->sas_ss_sp, current->sas_ss_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;
/* save i387 and extended state */
--
Regards/Gruss,
Boris.
SUSE Software Solutions Germany GmbH, GF: Felix Imendörffer, HRB 36809, AG Nürnberg
next prev parent reply other threads:[~2021-03-25 16:21 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
2021-03-25 16:20 ` Borislav Petkov [this message]
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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