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Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kDWFs-0007SN-DN; Wed, 02 Sep 2020 17:09:04 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kDWFn-0007RP-L3 for linux-arm-kernel@lists.infradead.org; Wed, 02 Sep 2020 17:09:02 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4D1BE1045; Wed, 2 Sep 2020 10:08:58 -0700 (PDT) Received: from arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F0CDB3F66F; Wed, 2 Sep 2020 10:08:56 -0700 (PDT) Date: Wed, 2 Sep 2020 18:08:54 +0100 From: Dave Martin To: Boyan Karatotev Subject: Re: [PATCH v2 3/4] kselftests/arm64: add PAuth test for whether exec() changes keys Message-ID: <20200902170854.GK6642@arm.com> References: <20200831110450.30188-1-boyan.karatotev@arm.com> <20200831110450.30188-4-boyan.karatotev@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200831110450.30188-4-boyan.karatotev@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200902_130900_218990_C5E2B820 X-CRM114-Status: GOOD ( 28.56 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Shuah Khan , boian4o1@gmail.com, Catalin Marinas , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, amit.kachhap@arm.com, vincenzo.frascino@arm.com, Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Aug 31, 2020 at 12:04:49PM +0100, Boyan Karatotev wrote: > Kernel documentation states that it will change PAuth keys on exec() calls. > > Verify that all keys are correctly switched to new ones. > > Cc: Shuah Khan > Cc: Catalin Marinas > Cc: Will Deacon > Reviewed-by: Vincenzo Frascino > Reviewed-by: Amit Daniel Kachhap > Signed-off-by: Boyan Karatotev > --- > tools/testing/selftests/arm64/pauth/Makefile | 4 + > .../selftests/arm64/pauth/exec_target.c | 35 +++++ > tools/testing/selftests/arm64/pauth/helper.h | 10 ++ > tools/testing/selftests/arm64/pauth/pac.c | 148 ++++++++++++++++++ > 4 files changed, 197 insertions(+) > create mode 100644 tools/testing/selftests/arm64/pauth/exec_target.c > > diff --git a/tools/testing/selftests/arm64/pauth/Makefile b/tools/testing/selftests/arm64/pauth/Makefile > index 5c0dd129562f..72e290b0b10c 100644 > --- a/tools/testing/selftests/arm64/pauth/Makefile > +++ b/tools/testing/selftests/arm64/pauth/Makefile > @@ -13,6 +13,7 @@ pauth_cc_support := $(shell if ($(CC) $(CFLAGS) -march=armv8.3-a -E -x c /dev/nu > ifeq ($(pauth_cc_support),1) > TEST_GEN_PROGS := pac > TEST_GEN_FILES := pac_corruptor.o helper.o > +TEST_GEN_PROGS_EXTENDED := exec_target > endif > > include ../../lib.mk > @@ -30,6 +31,9 @@ $(OUTPUT)/helper.o: helper.c > # greater, gcc emits pac* instructions which are not in HINT NOP space, > # preventing the tests from occurring at all. Compile for ARMv8.2 so tests can > # run on earlier targets and print a meaningful error messages > +$(OUTPUT)/exec_target: exec_target.c $(OUTPUT)/helper.o > + $(CC) $^ -o $@ $(CFLAGS) -march=armv8.2-a > + > $(OUTPUT)/pac: pac.c $(OUTPUT)/pac_corruptor.o $(OUTPUT)/helper.o > $(CC) $^ -o $@ $(CFLAGS) -march=armv8.2-a > endif > diff --git a/tools/testing/selftests/arm64/pauth/exec_target.c b/tools/testing/selftests/arm64/pauth/exec_target.c > new file mode 100644 > index 000000000000..07addef5a1d7 > --- /dev/null > +++ b/tools/testing/selftests/arm64/pauth/exec_target.c > @@ -0,0 +1,35 @@ > +// SPDX-License-Identifier: GPL-2.0 > +// Copyright (C) 2020 ARM Limited > + > +#include > +#include > +#include > + > +#include "helper.h" > + > + > +int main(void) > +{ > + struct signatures signed_vals; > + unsigned long hwcaps; > + size_t val; > + > + fread(&val, sizeof(size_t), 1, stdin); > + > + /* don't try to execute illegal (unimplemented) instructions) caller > + * should have checked this and keep worker simple > + */ > + hwcaps = getauxval(AT_HWCAP); > + > + if (hwcaps & HWCAP_PACA) { > + signed_vals.keyia = keyia_sign(val); > + signed_vals.keyib = keyib_sign(val); > + signed_vals.keyda = keyda_sign(val); > + signed_vals.keydb = keydb_sign(val); > + } > + signed_vals.keyg = (hwcaps & HWCAP_PACG) ? keyg_sign(val) : 0; > + > + fwrite(&signed_vals, sizeof(struct signatures), 1, stdout); > + > + return 0; > +} > diff --git a/tools/testing/selftests/arm64/pauth/helper.h b/tools/testing/selftests/arm64/pauth/helper.h > index e2ed910c9863..da6457177727 100644 > --- a/tools/testing/selftests/arm64/pauth/helper.h > +++ b/tools/testing/selftests/arm64/pauth/helper.h > @@ -6,6 +6,16 @@ > > #include > > +#define NKEYS 5 > + > + > +struct signatures { > + size_t keyia; > + size_t keyib; > + size_t keyda; > + size_t keydb; > + size_t keyg; > +}; > > void pac_corruptor(void); > > diff --git a/tools/testing/selftests/arm64/pauth/pac.c b/tools/testing/selftests/arm64/pauth/pac.c > index 035fdd6aae9b..1b9e3acfeb61 100644 > --- a/tools/testing/selftests/arm64/pauth/pac.c > +++ b/tools/testing/selftests/arm64/pauth/pac.c > @@ -2,6 +2,8 @@ > // Copyright (C) 2020 ARM Limited > > #include > +#include > +#include > #include > > #include "../../kselftest_harness.h" > @@ -33,6 +35,117 @@ do { \ > } while (0) > > > +void sign_specific(struct signatures *sign, size_t val) > +{ > + sign->keyia = keyia_sign(val); > + sign->keyib = keyib_sign(val); > + sign->keyda = keyda_sign(val); > + sign->keydb = keydb_sign(val); > +} > + > +void sign_all(struct signatures *sign, size_t val) > +{ > + sign->keyia = keyia_sign(val); > + sign->keyib = keyib_sign(val); > + sign->keyda = keyda_sign(val); > + sign->keydb = keydb_sign(val); > + sign->keyg = keyg_sign(val); > +} > + > +int are_same(struct signatures *old, struct signatures *new, int nkeys) > +{ > + int res = 0; > + > + res |= old->keyia == new->keyia; > + res |= old->keyib == new->keyib; > + res |= old->keyda == new->keyda; > + res |= old->keydb == new->keydb; > + if (nkeys == NKEYS) > + res |= old->keyg == new->keyg; > + > + return res; > +} > + > +int exec_sign_all(struct signatures *signed_vals, size_t val) > +{ > + int new_stdin[2]; > + int new_stdout[2]; > + int status; > + ssize_t ret; > + pid_t pid; Can we simplify this with popen(3)? Fork-and-exec is notoriously fiddly... [...] > +/* > + * fork() does not change keys. Only exec() does so call a worker program. > + * Its only job is to sign a value and report back the resutls > + */ > +TEST(exec_unique_keys) > +{ The kernel doesn't guarantee that keys are unique. Can we present all the "unique keys" wording differently, say exec_key_collision_likely() Otherwise people might infer from this test code that the keys are supposed to be truly unique and start reporting bugs on the kernel. I can't see an obvious security argument for unique keys (rather, the keys just need to be "unique enough". That's the job of get_random_bytes().) [...] Cheers ---Dave _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel