arm64: entry: Apply BP hardening for high-priority synchronous exceptions

Web:        https://git.kernel.org/torvalds/c/5dfc6ed27710c42cbc15db5c0d4475699991da0a
Commit:     5dfc6ed27710c42cbc15db5c0d4475699991da0a
Parent:     91b2d3442f6a44dce875670d702af22737ad5eff
Refname:    refs/heads/master
Author:     Will Deacon <[email protected]>
AuthorDate: Fri Feb 2 17:31:39 2018 +0000
Committer:  Catalin Marinas <[email protected]>
CommitDate: Tue Feb 6 22:53:44 2018 +0000

    arm64: entry: Apply BP hardening for high-priority synchronous exceptions
    
    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 <[email protected]>
    Reviewed-by: Marc Zyngier <[email protected]>
    Signed-off-by: Will Deacon <[email protected]>
    Signed-off-by: Catalin Marinas <[email protected]>
---
 arch/arm64/kernel/entry.S | 5 ++++-
 arch/arm64/mm/fault.c     | 9 +++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 4dd1b5a46642..af22793103af 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -767,7 +767,10 @@ el0_sp_pc:
 	 * Stack or PC alignment exception handling
 	 */
 	mrs	x26, far_el1
-	enable_daif
+	enable_da_f
+#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 af530eb9f2ed..43b28a782ed4 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -732,6 +732,12 @@ 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),
@@ -791,6 +797,9 @@ asmlinkage int __exception do_debug_exception(unsigned long addr,
 	if (interrupts_enabled(regs))
 		trace_hardirqs_off();
 
+	if (user_mode(regs) && instruction_pointer(regs) > TASK_SIZE)
+		arm64_apply_bp_hardening();
+
 	if (!inf->fn(addr, esr, regs)) {
 		rv = 1;
 	} else {
--
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