[PATCH v2 2/2] x86/mce/amd: Fix memory leak when `threshold_create_bank()` fails

[Ammar Faizi]

@bp is a local variable, calling mce_threshold_remove_device() when
threshold_create_bank() fails will not free the @bp. Note that
mce_threshold_remove_device() frees the @bp only if it's already
stored in the @threshold_banks per-CPU variable.

At that point, the @threshold_banks per-CPU variable is still NULL,
so the mce_threshold_remove_device() will just be a no-op and the
@bp is leaked.

Fix this by calling kfree() and early returning when we fail.

This bug is introduced by commit 6458de97fc15530b544 ("x86/mce/amd:
Straighten CPU hotplug path") [1].

Link: https://lore.kernel.org/all/20200403161943.1458-6-bp@xxxxxxxxx [1]

Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Fixes: 6458de97fc15530b54477c4e2b70af653e8ac3d9 ("x86/mce/amd: Straighten CPU hotplug path")
Cc: stable@xxxxxxxxxxxxxxx # v5.8+
Signed-off-by: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
---
 arch/x86/kernel/cpu/mce/amd.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index 9f4b508886dd..75d019dfe8d6 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -1350,15 +1350,14 @@ 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) {
+			kfree(bp);
+			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