linux-kernel - [PATCH 2/5] riscv: misaligned: enable IRQs while handling misaligned accesses

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Message-ID: <20250414123543.1615478-3-cleger@rivosinc.com>
Date: Mon, 14 Apr 2025 14:34:42 +0200
From: Clément Léger <cleger@...osinc.com>
To: linux-doc@...r.kernel.org (open list:DOCUMENTATION),
	linux-kernel@...r.kernel.org (open list),
	linux-riscv@...ts.infradead.org (open list:RISC-V ARCHITECTURE),
	linux-kselftest@...r.kernel.org (open list:KERNEL SELFTEST FRAMEWORK)
Cc: Clément Léger <cleger@...osinc.com>,
	Jonathan Corbet <corbet@....net>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Alexandre Ghiti <alex@...ti.fr>,
	Shuah Khan <shuah@...nel.org>,
	Andrew Jones <ajones@...tanamicro.com>,
	Samuel Holland <samuel.holland@...ive.com>
Subject: [PATCH 2/5] riscv: misaligned: enable IRQs while handling misaligned accesses

We can safely reenable IRQs if they were enabled in the previous
context. This allows to access user memory that could potentially
trigger a page fault.

Fixes: b686ecdeacf6 ("riscv: misaligned: Restrict user access to kernel memory")
Signed-off-by: Clément Léger <cleger@...osinc.com>
---
 arch/riscv/kernel/traps.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 55d9f3450398..3eecc2addc41 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -206,6 +206,11 @@ enum misaligned_access_type {
 static void do_trap_misaligned(struct pt_regs *regs, enum misaligned_access_type type)
 {
 	irqentry_state_t state = irqentry_enter(regs);
+	bool enable_irqs = !regs_irqs_disabled(regs);
+
+	/* Enable interrupts if they were enabled in the interrupted context. */
+	if (enable_irqs)
+		local_irq_enable();
 
 	if (type ==  MISALIGNED_LOAD) {
 		if (handle_misaligned_load(regs))
@@ -217,6 +222,9 @@ static void do_trap_misaligned(struct pt_regs *regs, enum misaligned_access_type
 				      "Oops - store (or AMO) address misaligned");
 	}
 
+	if (enable_irqs)
+		local_irq_disable();
+
 	irqentry_exit(regs, state);
 }
 
-- 
2.49.0