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From: Peter Collingbourne <pcc@google.com>
To: Kristina Martsenko <kristina.martsenko@arm.com>,
	 Vincenzo Frascino <Vincenzo.Frascino@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	 Will Deacon <will@kernel.org>, Dave Martin <Dave.Martin@arm.com>
Cc: Peter Collingbourne <pcc@google.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: [PATCH] arm64: reject prctl(PR_PAC_RESET_KEYS) on compat tasks
Date: Tue, 13 Oct 2020 22:24:30 -0700	[thread overview]
Message-ID: <20201014052430.11630-1-pcc@google.com> (raw)

It doesn't make sense to issue prctl(PR_PAC_RESET_KEYS) on a
compat task because the 32-bit instruction set does not offer PAuth
instructions. For consistency with other 64-bit only prctls such as
{SET,GET}_TAGGED_ADDR_CTRL, reject the prctl on compat tasks.

Although this is a userspace-visible change, maybe it isn't too late
to make this change given that the hardware isn't available yet and
it's very unlikely that anyone has 32-bit software that actually
depends on this succeeding.

Link: https://linux-review.googlesource.com/id/Ie885a1ff84ab498cc9f62d6451e9f2cfd4b1d06a
Signed-off-by: Peter Collingbourne <pcc@google.com>
---
 arch/arm64/kernel/pointer_auth.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kernel/pointer_auth.c b/arch/arm64/kernel/pointer_auth.c
index 1e77736a4f66..245c3ee97ed8 100644
--- a/arch/arm64/kernel/pointer_auth.c
+++ b/arch/arm64/kernel/pointer_auth.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 
+#include <linux/compat.h>
 #include <linux/errno.h>
 #include <linux/prctl.h>
 #include <linux/random.h>
@@ -17,6 +18,9 @@ int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg)
 	if (!system_supports_address_auth() && !system_supports_generic_auth())
 		return -EINVAL;
 
+	if (is_compat_task())
+		return -EINVAL;
+
 	if (!arg) {
 		ptrauth_keys_init_user(keys);
 		return 0;
-- 
2.28.0.1011.ga647a8990f-goog


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             reply	other threads:[~2020-10-14  5:26 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-14  5:24 Peter Collingbourne [this message]
2020-10-14  9:53 ` [PATCH] arm64: reject prctl(PR_PAC_RESET_KEYS) on compat tasks Dave Martin
2020-10-14 17:45   ` Peter Collingbourne
2020-10-14 18:00     ` Dave Martin
2020-10-15 10:46 ` Will Deacon
2020-10-15 20:40 ` Will Deacon

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