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From: Thomas Garnier <thgarnie@google.com>
To: "Martin Schwidefsky" <schwidefsky@de.ibm.com>,
	"Heiko Carstens" <heiko.carstens@de.ibm.com>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Dave Hansen" <dave.hansen@intel.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Thomas Garnier" <thgarnie@google.com>,
	"David Howells" <dhowells@redhat.com>,
	"René Nyffenegger" <mail@renenyffenegger.ch>,
	"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
	"Ingo Molnar" <mingo@kernel.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Oleg Nesterov" <oleg@redhat.com>,
	"Stephen Smalley" <sds@tycho.nsa.gov>,
	"Pavel Tikhomirov" <ptikhomirov@virtuozzo.com>,
	"Ingo Molnar" <mingo@redhat.com>,
	"H . Peter Anvin" <hpa@zytor.com>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Rik van Riel" <riel@redhat.com>,
	"Josh Poimboeuf" <jpoimboe@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>, "Brian Gerst" <brgerst@gma>
Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-api@vger.kernel.org, x86@kernel.org,
	linux-arm-kernel@lists.infradead.org,
	kernel-hardening@lists.openwall.com
Subject: [PATCH v7 4/4] arm64/syscalls: Architecture specific pre-usermode check
Date: Mon, 10 Apr 2017 09:44:20 -0700	[thread overview]
Message-ID: <20170410164420.64003-4-thgarnie@google.com> (raw)
In-Reply-To: <20170410164420.64003-1-thgarnie@google.com>

Disable the generic pre-usermode check in favor of an optimized
implementation. This patch adds specific checks on user-mode return path
to make it faster and smaller.

The address limit is checked on each syscall return path to user-mode.
If it was changed, a generic handler is called to stop the kernel on an
explicit check.

Signed-off-by: Thomas Garnier <thgarnie@google.com>
---
Based on next-20170410
---
 arch/arm64/Kconfig        |  1 +
 arch/arm64/kernel/entry.S | 13 +++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 9b8fcab7da56..3f9e8e7d9376 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -24,6 +24,7 @@ config ARM64
 	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
+	select ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE
 	select ARM_AMBA
 	select ARM_ARCH_TIMER
 	select ARM_GIC
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 43512d4d7df2..bdd094c7837a 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -744,6 +744,8 @@ ENDPROC(cpu_switch_to)
 ret_fast_syscall:
 	disable_irq				// disable interrupts
 	str	x0, [sp, #S_X0]			// returned x0
+	ldr	x2, [tsk, #TSK_TI_ADDR_LIMIT]	// check addr limit change
+	tbnz	x2, #63, addr_limit_fail
 	ldr	x1, [tsk, #TSK_TI_FLAGS]	// re-check for syscall tracing
 	and	x2, x1, #_TIF_SYSCALL_WORK
 	cbnz	x2, ret_fast_syscall_trace
@@ -771,6 +773,9 @@ work_pending:
  */
 ret_to_user:
 	disable_irq				// disable interrupts
+	ldr	x2, [tsk, #TSK_TI_ADDR_LIMIT]	// check addr limit change
+	tbnz	x2, #63, addr_limit_fail
+
 	ldr	x1, [tsk, #TSK_TI_FLAGS]
 	and	x2, x1, #_TIF_WORK_MASK
 	cbnz	x2, work_pending
@@ -780,6 +785,14 @@ finish_ret_to_user:
 ENDPROC(ret_to_user)
 
 /*
+ * Address limit was incorrect before returning in user-mode which could be
+ * used to elevate privileges. Call the generic handler to stop the kernel on
+ * the appropriate check. This function does not return.
+ */
+addr_limit_fail:
+	bl address_limit_check_failed
+
+/*
  * This is how we return from a fork.
  */
 ENTRY(ret_from_fork)
-- 
2.12.2.715.g7642488e1d-goog

  parent reply	other threads:[~2017-04-10 16:44 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-10 16:44 [PATCH v7 1/4] syscalls: Restore address limit after a syscall Thomas Garnier
2017-04-10 16:44 ` [PATCH v7 3/4] arm/syscalls: Architecture specific pre-usermode check Thomas Garnier
2017-04-10 16:44 ` Thomas Garnier [this message]
2017-04-10 17:12   ` [PATCH v7 4/4] arm64/syscalls: " Catalin Marinas
     [not found]     ` <20170410171240.GE30647-M2fw3Uu6cmfZROr8t4l/smS4ubULX0JqMm0uRHvK7Nw@public.gmane.org>
2017-04-10 20:06       ` Thomas Garnier
     [not found]         ` <20170410200622.8654-1-thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2017-04-10 20:09           ` Thomas Garnier
2017-04-10 20:07       ` Thomas Garnier
     [not found] ` <20170410164420.64003-1-thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2017-04-10 16:44   ` [PATCH v7 2/4] x86/syscalls: " Thomas Garnier
2017-04-24 23:57   ` [PATCH v7 1/4] syscalls: Restore address limit after a syscall Kees Cook
     [not found]     ` <CAGXu5j+J67zC9tcncacHTDvXKMF3HZuPCivk-Uz4J6h-cEv-qQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-04-25  6:23       ` Ingo Molnar
     [not found]         ` <20170425062324.pdpi5v7ypobw74ki-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-04-25 14:12           ` Thomas Garnier
2017-04-25  6:33   ` Ingo Molnar
     [not found]     ` <20170425063305.hwjuxupa37rwe6zj-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-04-25 14:18       ` Thomas Garnier
2017-04-26  8:12         ` Ingo Molnar
     [not found]           ` <20170426081229.6wnugrs7w3at4xry-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-04-26 14:09             ` Thomas Garnier

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