Re: [PATCH v4 2/2] x86/mce/amd: Fix memory leak when `threshold_create_bank()` fails

Alviro Iskandar Setiawan
2022-03-03T01:58:45Z

On Thu, 3 Mar 2022 06:27:33 +0700, Ammar Faizi wrote:
> +static void _mce_threshold_remove_device(struct threshold_bank **bp)
> +{
> + unsigned int bank, numbanks = this_cpu_read(mce_num_banks);
> +
> + for (bank = 0; bank < numbanks; bank++) {
> + if (bp[bank]) {
> + threshold_remove_bank(bp[bank]);
> + bp[bank] = NULL;
> + }
> + }
> + kfree(bp);
> +}

hi sir, i think this can be improved again, we can avoid calling
this_cpu_read(mce_num_banks) twice if we pass the numbanks as an
argument, plz review the changes below

diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index 9f4b508886dd..e492efab68a2 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -1293,10 +1293,23 @@ static void threshold_remove_bank(struct threshold_bank *bank)
kfree(bank);
}

+static void _mce_threshold_remove_device(struct threshold_bank **bp,
+ unsigned int numbanks)
+{
+ unsigned int bank;
+
+ for (bank = 0; bank < numbanks; bank++) {
+ if (bp[bank]) {
+ threshold_remove_bank(bp[bank]);
+ bp[bank] = NULL;
+ }
+ }
+ kfree(bp);
+}
+
int mce_threshold_remove_device(unsigned int cpu)
{
struct threshold_bank **bp = this_cpu_read(threshold_banks);
- unsigned int bank, numbanks = this_cpu_read(mce_num_banks);

if (!bp)
return 0;
@@ -1307,13 +1320,7 @@ int mce_threshold_remove_device(unsigned int cpu)
*/
this_cpu_write(threshold_banks, NULL);

- for (bank = 0; bank < numbanks; bank++) {
- if (bp[bank]) {
- threshold_remove_bank(bp[bank]);
- bp[bank] = NULL;
- }
- }
- kfree(bp);
+ _mce_threshold_remove_device(bp, this_cpu_read(mce_num_banks));
return 0;
}

@@ -1350,15 +1357,14 @@ int mce_threshold_create_device(unsigned int cpu)
if (!(this_cpu_read(bank_map) & (1 << bank)))
continue;
err = threshold_create_bank(bp, cpu, bank);
- if (err)
- goto out_err;
+ if (err) {
+ _mce_threshold_remove_device(bp, numbanks);
+ return err;
+ }
}
this_cpu_write(threshold_banks, bp);

if (thresholding_irq_en)
mce_threshold_vector = amd_threshold_interrupt;
return 0;
-out_err:
- mce_threshold_remove_device(cpu);
- return err;
}

-- Viro