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Subject[PATCH] arm64/smp: check !ipi_desc[i] in arch_show_interrupts
Date
There is a potential dereferencing null pointer issue in
arch_show_interrupts.

Problem 1:
int arch_show_interrupts(struct seq_file *p, int prec)
for (i = 0; i < NR_IPI; i++) {
seq_printf(p, "%10u ", irq_desc_kstat_cpu(ipi_desc[i],
cpu));

Only ipi_desc[0..nr_ipi - 1] are initialized in set_smp_ipi_range.
and ipi_desc[nr_ipi..NR_IPI] are NULL.
irq_desc_kstat_cpu will dereference NULL pointer.
For now, the problem can not be triggered, because NR_IPI is always
equal to nr_ipi.

Problem 2:
If request_percpu_irq failed in set_smp_ipi_range, ipi_desc[i]
would be NULL.
irq_desc_kstat_cpu will dereference NULL pointer.

check !ipi_desc[i] (as arm does) to avoid the problem.

Signed-off-by: Chen Jun <chenjun102@huawei.com>
---
arch/arm64/kernel/smp.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 62ed361a4376..3d54f464428b 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -781,6 +781,9 @@ int arch_show_interrupts(struct seq_file *p, int prec)
unsigned int cpu, i;

for (i = 0; i < NR_IPI; i++) {
+ if (!ipi_desc[i])
+ continue;
+
seq_printf(p, "%*s%u:%s", prec - 1, "IPI", i,
prec >= 4 ? " " : "");
for_each_online_cpu(cpu)
--
2.17.1
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