2022-05-28 09:48:18

by Chen Jun

Subject: [PATCH] arm64/smp: check !ipi_desc[i] in arch_show_interrupts

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 <[email protected]>
---
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

2022-06-09 15:36:33

by Will Deacon

Subject: Re: [PATCH] arm64/smp: check !ipi_desc[i] in arch_show_interrupts

On Fri, May 27, 2022 at 08:22:36AM +0000, Chen Jun wrote:
> 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 <[email protected]>
> ---
> 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;

Why not just use nr_ipi instead of NR_IPI?

Will

2022-06-15 12:50:59

by Chen Jun

Subject: Re: [PATCH] arm64/smp: check !ipi_desc[i] in arch_show_interrupts

$B:_(B 2022/6/9 23:20, Will Deacon $B<LF;(B:
> On Fri, May 27, 2022 at 08:22:36AM +0000, Chen Jun wrote:
>> 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 <[email protected]>
>> ---
>> 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;
>
> Why not just use nr_ipi instead of NR_IPI?

Yee, that is what I do at first. But I noticed that:

void __init set_smp_ipi_range(int ipi_base, int n)
for (i = 0; i < nr_ipi; i++) {
err = request_percpu_irq(ipi_base + i, ipi_handler,
"IPI", &cpu_number);
WARN_ON(err);
ipi_desc[i] = irq_to_desc(ipi_base + i);

If request_percpu_irq return a error, I not sure if ipi_desc[i] makes sense.

>
> Will
>

--
Regards
Chen Jun