linux-kernel - [PATCH 5/9] x86, pkeys, selftests: fix pointer math

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Message-Id: <20180323180913.7CA6F44E@viggo.jf.intel.com>
Date:   Fri, 23 Mar 2018 11:09:13 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, Dave Hansen <dave.hansen@...ux.intel.com>,
        linuxram@...ibm.com, tglx@...utronix.de, dave.hansen@...el.com,
        mpe@...erman.id.au, mingo@...nel.org, akpm@...ux-foundation.org,
        shuah@...nel.org
Subject: [PATCH 5/9] x86, pkeys, selftests: fix pointer math


From: Dave Hansen <dave.hansen@...ux.intel.com>

We dump out the entire area of the siginfo where the
si_pkey_ptr is supposed to be.  But, we do some math
on the poitner, which is a u32.  We intended to do
byte math, not u32 math on the pointer.

Cast it over to a u8* so it works.

Also, move this block of code to below th si_code
check.  It doesn't hurt anything, but the si_pkey
field is gibberish for other signal types.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Ram Pai <linuxram@...ibm.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Michael Ellermen <mpe@...erman.id.au>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Shuah Khan <shuah@...nel.org>
---

 b/tools/testing/selftests/x86/protection_keys.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff -puN tools/testing/selftests/x86/protection_keys.c~pkeys-selftests-fix-pointer-math tools/testing/selftests/x86/protection_keys.c
--- a/tools/testing/selftests/x86/protection_keys.c~pkeys-selftests-fix-pointer-math	2018-03-21 15:47:50.374198921 -0700
+++ b/tools/testing/selftests/x86/protection_keys.c	2018-03-21 15:47:50.377198921 -0700
@@ -289,13 +289,6 @@ void signal_handler(int signum, siginfo_
 		dump_mem(pkru_ptr - 128, 256);
 	pkey_assert(*pkru_ptr);
 
-	si_pkey_ptr = (u32 *)(((u8 *)si) + si_pkey_offset);
-	dprintf1("si_pkey_ptr: %p\n", si_pkey_ptr);
-	dump_mem(si_pkey_ptr - 8, 24);
-	siginfo_pkey = *si_pkey_ptr;
-	pkey_assert(siginfo_pkey < NR_PKEYS);
-	last_si_pkey = siginfo_pkey;
-
 	if ((si->si_code == SEGV_MAPERR) ||
 	    (si->si_code == SEGV_ACCERR) ||
 	    (si->si_code == SEGV_BNDERR)) {
@@ -303,6 +296,13 @@ void signal_handler(int signum, siginfo_
 		exit(4);
 	}
 
+	si_pkey_ptr = (u32 *)(((u8 *)si) + si_pkey_offset);
+	dprintf1("si_pkey_ptr: %p\n", si_pkey_ptr);
+	dump_mem((u8 *)si_pkey_ptr - 8, 24);
+	siginfo_pkey = *si_pkey_ptr;
+	pkey_assert(siginfo_pkey < NR_PKEYS);
+	last_si_pkey = siginfo_pkey;
+
 	dprintf1("signal pkru from xsave: %08x\n", *pkru_ptr);
 	/* need __rdpkru() version so we do not do shadow_pkru checking */
 	dprintf1("signal pkru from  pkru: %08x\n", __rdpkru());
_