Subject: [PATCH AUTOSEL 5.10 12/21] arm64: kprobes: Restore local irqflag if kprobes is cancelled

From: Sasha Levin <[email-masked]>
Date: Mon, 19 Apr 2021 16:44:10 -0400

From: Jisheng Zhang <[email-masked]>

[ Upstream commit 738fa58ee1328481d1d7889e7c430b3401c571b9 ]

If instruction being single stepped caused a page fault, the kprobes
is cancelled to let the page fault handler continue as a normal page
fault. But the local irqflags are disabled so cpu will restore pstate
with DAIF masked. After pagefault is serviced, the kprobes is
triggerred again, we overwrite the saved_irqflag by calling
kprobes_save_local_irqflag(). NOTE, DAIF is masked in this new saved
irqflag. After kprobes is serviced, the cpu pstate is retored with
DAIF masked.

This patch is inspired by one patch for riscv from Liao Chang.

Signed-off-by: Jisheng Zhang <[email-masked]>
Acked-by: Masami Hiramatsu <[email-masked]>
Link: https://lore.kernel.org/r/[email-masked]
Signed-off-by: Will Deacon <[email-masked]>
Signed-off-by: Sasha Levin <[email-masked]>
---
 arch/arm64/kernel/probes/kprobes.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index f11a1a1f7026..798c3e78b84b 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -286,10 +286,12 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 		if (!instruction_pointer(regs))
 			BUG();
 
-		if (kcb->kprobe_status == KPROBE_REENTER)
+		if (kcb->kprobe_status == KPROBE_REENTER) {
 			restore_previous_kprobe(kcb);
-		else
+		} else {
+			kprobes_restore_local_irqflag(kcb, regs);
 			reset_current_kprobe();
+		}
 
 		break;
 	case KPROBE_HIT_ACTIVE:
-- 
2.30.2

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