[PATCH] powerpc/irq: fix stack overflow verification

[PATCH] powerpc/irq: fix stack overflow verification

[Christophe Leroy]

Before commit 0366a1c70b89 ("powerpc/irq: Run softirqs off the top of
the irq stack"), check_stack_overflow() was called by do_IRQ(), before
switching to the irq stack.
In that commit, do_IRQ() was renamed __do_irq(), and is now executing
on the irq stack, so check_stack_overflow() has just become almost
useless.

Move check_stack_overflow() call in do_IRQ() to do the check while
still on the current stack.

Fixes: 0366a1c70b89 ("powerpc/irq: Run softirqs off the top of the irq stack")
Cc: stable@vger.kernel.org
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/kernel/irq.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 0aebd7843c73..e2bce937d51f 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -667,8 +667,6 @@ void __do_irq(struct pt_regs *regs)
 
 	trace_irq_entry(regs);
 
-	check_stack_overflow();
-
 	/*
 	 * Query the platform PIC for the interrupt & ack it.
 	 *
@@ -701,6 +699,8 @@ void do_IRQ(struct pt_regs *regs)
 	irqsp = hardirq_ctx[raw_smp_processor_id()];
 	sirqsp = softirq_ctx[raw_smp_processor_id()];
 
+	check_stack_overflow();
+
 	/* Already there ? */
 	if (unlikely(cursp == irqsp || cursp == sirqsp)) {
 		__do_irq(regs);
-- 
2.13.3

Re: [PATCH] powerpc/irq: fix stack overflow verification

[Michael Ellerman]

On Mon, 2019-12-09 at 06:19:08 UTC, Christophe Leroy wrote:
> Before commit 0366a1c70b89 ("powerpc/irq: Run softirqs off the top of
> the irq stack"), check_stack_overflow() was called by do_IRQ(), before
> switching to the irq stack.
> In that commit, do_IRQ() was renamed __do_irq(), and is now executing
> on the irq stack, so check_stack_overflow() has just become almost
> useless.
> 
> Move check_stack_overflow() call in do_IRQ() to do the check while
> still on the current stack.
> 
> Fixes: 0366a1c70b89 ("powerpc/irq: Run softirqs off the top of the irq stack")
> Cc: stable@vger.kernel.org
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/099bc4812f09155da77eeb960a983470249c9ce1

cheers