[PATCH] x86/mpx, selftests: Only check bounds-vs-shadow when we keep shadow

[PATCH] x86/mpx, selftests: Only check bounds-vs-shadow when we keep shadow

[Joerg Roedel]

From: Joerg Roedel <jroedel@suse.de>

The check between the hardware state and our shadow of it is
checked in the signal handler for all bounds exceptions,
even for the ones where we don't keep the shadow up2date.
This is a problem because when no shadow is kept the handler
fails at this point and hides the real reason of the
exception.

Move the check into the code-path evaluating normal bounds
exceptions to prevent this.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 tools/testing/selftests/x86/mpx-mini-test.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/x86/mpx-mini-test.c b/tools/testing/selftests/x86/mpx-mini-test.c
index 616ee96..a8df159 100644
--- a/tools/testing/selftests/x86/mpx-mini-test.c
+++ b/tools/testing/selftests/x86/mpx-mini-test.c
@@ -404,8 +404,6 @@ void handler(int signum, siginfo_t *si, void *vucontext)
 		dprintf2("info->si_lower: %p\n", __si_bounds_lower(si));
 		dprintf2("info->si_upper: %p\n", __si_bounds_upper(si));
 
-		check_siginfo_vs_shadow(si);
-
 		for (i = 0; i < 8; i++)
 			dprintf3("[%d]: %p\n", i, si_addr_ptr[i]);
 		switch (br_reason) {
@@ -416,6 +414,9 @@ void handler(int signum, siginfo_t *si, void *vucontext)
 			exit(5);
 		case 1: /* #BR MPX bounds exception */
 			/* these are normal and we expect to see them */
+
+			check_siginfo_vs_shadow(si);
+
 			dprintf1("bounds exception (normal): status 0x%jx at %p si_addr: %p\n",
 				status, (void *)ip, si->si_addr);
 			num_bnd_chk++;
-- 
1.9.1

[tip:x86/mm] x86/mpx, selftests: Only check bounds-vs-shadow when we keep shadow

[tip-bot for Joerg Roedel]

Commit-ID:  5f2173e056b2a5c215b862f136192744c447844e
Gitweb:     http://git.kernel.org/tip/5f2173e056b2a5c215b862f136192744c447844e
Author:     Joerg Roedel <jroedel@suse.de>
AuthorDate: Thu, 6 Apr 2017 16:23:18 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 12 Apr 2017 08:40:59 +0200

x86/mpx, selftests: Only check bounds-vs-shadow when we keep shadow

The check between the hardware state and our shadow of it is
checked in the signal handler for all bounds exceptions,
even for the ones where we don't keep the shadow up2date.
This is a problem because when no shadow is kept the handler
fails at this point and hides the real reason of the
exception.

Move the check into the code-path evaluating normal bounds
exceptions to prevent this.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kselftest@vger.kernel.org
Link: http://lkml.kernel.org/r/1491488598-27346-1-git-send-email-joro@8bytes.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 tools/testing/selftests/x86/mpx-mini-test.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/x86/mpx-mini-test.c b/tools/testing/selftests/x86/mpx-mini-test.c
index 616ee96..a8df159 100644
--- a/tools/testing/selftests/x86/mpx-mini-test.c
+++ b/tools/testing/selftests/x86/mpx-mini-test.c
@@ -404,8 +404,6 @@ void handler(int signum, siginfo_t *si, void *vucontext)
 		dprintf2("info->si_lower: %p\n", __si_bounds_lower(si));
 		dprintf2("info->si_upper: %p\n", __si_bounds_upper(si));
 
-		check_siginfo_vs_shadow(si);
-
 		for (i = 0; i < 8; i++)
 			dprintf3("[%d]: %p\n", i, si_addr_ptr[i]);
 		switch (br_reason) {
@@ -416,6 +414,9 @@ void handler(int signum, siginfo_t *si, void *vucontext)
 			exit(5);
 		case 1: /* #BR MPX bounds exception */
 			/* these are normal and we expect to see them */
+
+			check_siginfo_vs_shadow(si);
+
 			dprintf1("bounds exception (normal): status 0x%jx at %p si_addr: %p\n",
 				status, (void *)ip, si->si_addr);
 			num_bnd_chk++;

Re: [PATCH] x86/mpx, selftests: Only check bounds-vs-shadow when we keep shadow

[Dave Hansen]

On 04/06/2017 07:23 AM, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@suse.de>
> 
> The check between the hardware state and our shadow of it is
> checked in the signal handler for all bounds exceptions,
> even for the ones where we don't keep the shadow up2date.
> This is a problem because when no shadow is kept the handler
> fails at this point and hides the real reason of the
> exception.
> 
> Move the check into the code-path evaluating normal bounds
> exceptions to prevent this.

Looks good to me.

Acked-by: Dave Hansen <dave.hansen@linux.intel.com>