[PATCH AUTOSEL 6.18-6.12] riscv: panic if IRQ handler stacks cannot be allocated

[Sasha Levin]

From: Osama Abdelkader <osama.abdelkader@xxxxxxxxx>

[ Upstream commit 2abd0dba562551d5c27f97ce560684f534c0cf3a ]

init_irq_stacks() and init_irq_scs() may fail when arch_alloc_vmap_stack
or scs_alloc return NULL, call panic() in this case.

Signed-off-by: Osama Abdelkader <osama.abdelkader@xxxxxxxxx>
Link: https://patch.msgid.link/20260404185522.21767-1-osama.abdelkader@xxxxxxxxx
Signed-off-by: Paul Walmsley <pjw@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---

LLM Generated explanations, may be completely bogus:

The branch check finished: `2abd0dba56255` ("riscv: panic if IRQ handler
stacks cannot be allocated") is on `master` and the `-next` integration
branches, but not on the current `v6.18.44` stable tree. That matches
the earlier **YES** backport recommendation — the fix is mainline-only
and still needs to be cherry-picked into 6.18.y.

 arch/riscv/kernel/irq.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
index b6af20bc300f5..017d42e778be6 100644
--- a/arch/riscv/kernel/irq.c
+++ b/arch/riscv/kernel/irq.c
@@ -75,28 +75,34 @@ DECLARE_PER_CPU(ulong *, irq_shadow_call_stack_ptr);
 DEFINE_PER_CPU(ulong *, irq_shadow_call_stack_ptr);
 #endif
 
-static void init_irq_scs(void)
+static void __init init_irq_scs(void)
 {
 	int cpu;
+	void *s;
 
 	if (!scs_is_enabled())
 		return;
 
-	for_each_possible_cpu(cpu)
-		per_cpu(irq_shadow_call_stack_ptr, cpu) =
-			scs_alloc(cpu_to_node(cpu));
+	for_each_possible_cpu(cpu) {
+		s = scs_alloc(cpu_to_node(cpu));
+		if (!s)
+			panic("Failed to allocate IRQ shadow call stack resources\n");
+		per_cpu(irq_shadow_call_stack_ptr, cpu) = s;
+	}
 }
 
 DEFINE_PER_CPU(ulong *, irq_stack_ptr);
 
 #ifdef CONFIG_VMAP_STACK
-static void init_irq_stacks(void)
+static void __init init_irq_stacks(void)
 {
 	int cpu;
 	ulong *p;
 
 	for_each_possible_cpu(cpu) {
 		p = arch_alloc_vmap_stack(IRQ_STACK_SIZE, cpu_to_node(cpu));
+		if (!p)
+			panic("Failed to allocate IRQ stack resources\n");
 		per_cpu(irq_stack_ptr, cpu) = p;
 	}
 }
@@ -104,7 +110,7 @@ static void init_irq_stacks(void)
 /* irq stack only needs to be 16 byte aligned - not IRQ_STACK_SIZE aligned. */
 DEFINE_PER_CPU_ALIGNED(ulong [IRQ_STACK_SIZE/sizeof(ulong)], irq_stack);
 
-static void init_irq_stacks(void)
+static void __init init_irq_stacks(void)
 {
 	int cpu;
 
@@ -129,8 +135,8 @@ void do_softirq_own_stack(void)
 #endif /* CONFIG_SOFTIRQ_ON_OWN_STACK */
 
 #else
-static void init_irq_scs(void) {}
-static void init_irq_stacks(void) {}
+static void __init init_irq_scs(void) {}
+static void __init init_irq_stacks(void) {}
 #endif /* CONFIG_IRQ_STACKS */
 
 int arch_show_interrupts(struct seq_file *p, int prec)
-- 
2.53.0