[PATCH v4.4 21/45] arm64: entry: Apply BP hardening for high-priority synchronous exceptions

From: Viresh Kumar <viresh.kumar@linaro.org>
To: linux-arm-kernel@lists.infradead.org,
	Julien Thierry <Julien.Thierry@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Will Deacon <will.deacon@arm.com>,
	stable@vger.kernel.org, mark.brown@arm.com,
	Catalin Marinas <catalin.marinas@arm.com>,
	Russell King <rmk+kernel@arm.linux.org.uk>
Subject: [PATCH v4.4 21/45] arm64: entry: Apply BP hardening for high-priority synchronous exceptions
Date: Fri, 14 Jun 2019 08:38:04 +0530	[thread overview]
Message-ID: <342eec766d9748b0c9fb4a5da48220052a5426e6.1560480942.git.viresh.kumar@linaro.org> (raw)
In-Reply-To: <cover.1560480942.git.viresh.kumar@linaro.org>

From: Will Deacon <will.deacon@arm.com>

commit 5dfc6ed27710c42cbc15db5c0d4475699991da0a upstream.

Software-step and PC alignment fault exceptions have higher priority than
instruction abort exceptions, so apply the BP hardening hooks there too
if the user PC appears to reside in kernel space.

Reported-by: Dan Hettena <dhettena@nvidia.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
[ v4.4: Resolved rebase conflicts ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 arch/arm64/kernel/entry.S | 6 ++++--
 arch/arm64/mm/fault.c     | 9 +++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 05bfc71639fc..42a141f01f3b 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -530,8 +530,10 @@ ENDPROC(el1_irq)
 	 * Stack or PC alignment exception handling
 	 */
 	mrs	x26, far_el1
-	// enable interrupts before calling the main handler
-	enable_dbg_and_irq
+	enable_dbg
+#ifdef CONFIG_TRACE_IRQFLAGS
+	bl	trace_hardirqs_off
+#endif
 	ct_user_exit
 	mov	x0, x26
 	mov	x1, x25
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 1878c881a247..082f385b6592 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -561,6 +561,12 @@ asmlinkage void __exception do_sp_pc_abort(unsigned long addr,
 	struct siginfo info;
 	struct task_struct *tsk = current;
 
+	if (user_mode(regs)) {
+		if (instruction_pointer(regs) > TASK_SIZE)
+			arm64_apply_bp_hardening();
+		local_irq_enable();
+	}
+
 	if (show_unhandled_signals && unhandled_signal(tsk, SIGBUS))
 		pr_info_ratelimited("%s[%d]: %s exception: pc=%p sp=%p\n",
 				    tsk->comm, task_pid_nr(tsk),
@@ -621,6 +627,9 @@ asmlinkage int __exception do_debug_exception(unsigned long addr_if_watchpoint,
 	if (interrupts_enabled(regs))
 		trace_hardirqs_off();
 
+	if (user_mode(regs) && instruction_pointer(regs) > TASK_SIZE)
+		arm64_apply_bp_hardening();
+
 	if (!inf->fn(addr_if_watchpoint, esr, regs)) {
 		rv = 1;
 	} else {
-- 
2.21.0.rc0.269.g1a574e7a288b


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