[PATCH v5 2/2] x86/MCE/AMD: Fix memory leak when `threshold_create_bank()` fails

Ammar Faizi
2022-03-10T01:54:06Z

In mce_threshold_create_device(), if threshold_create_bank() fails, the
@bp will be leaked, because the call to mce_threshold_remove_device()
will not free the @bp. mce_threshold_remove_device() frees
@threshold_banks. At that point, the @bp has not been written to
@threshold_banks, @threshold_banks is NULL, so the call is just a nop.

Fix this by extracting the cleanup part into a new static function
_mce_threshold_remove_device(), then call it from create/remove device
functions.

Also, eliminate the "goto out_err", just early return inside the loop
if the creation fails.

Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org # v5.8+
Fixes: 6458de97fc15 ("x86/mce/amd: Straighten CPU hotplug path")
Link: https://lore.kernel.org/lkml/9dfe087a-f941-1bc4-657d-7e7c198888ff@gnuweeb.org
Co-authored-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>
Signed-off-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>
Co-authored-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
---
arch/x86/kernel/cpu/mce/amd.c | 32 +++++++++++++++++++-------------
1 file changed, 19 insertions(+), 13 deletions(-)

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;
}
--
2.32.0