[tip: ras/core] x86/MCE/AMD: Fix memory leak when threshold_create_bank() fails

[tip-bot2 for Ammar Faizi]

The following commit has been merged into the ras/core branch of tip:

Commit-ID:     e5f28623ceb103e13fc3d7bd45edf9818b227fd0
Gitweb:        https://git.kernel.org/tip/e5f28623ceb103e13fc3d7bd45edf9818b227fd0
Author:        Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
AuthorDate:    Tue, 29 Mar 2022 17:47:05 +07:00
Committer:     Borislav Petkov <bp@xxxxxxx>
CommitterDate: Tue, 05 Apr 2022 21:24:37 +02:00

x86/MCE/AMD: Fix memory leak when threshold_create_bank() fails

In mce_threshold_create_device(), if threshold_create_bank() fails, the
previously allocated threshold banks array @bp will be leaked because
the call to mce_threshold_remove_device() will not free it.

This happens because mce_threshold_remove_device() fetches the pointer
through the threshold_banks per-CPU variable but bp is written there
only after the bank creation is successful, and not before, when
threshold_create_bank() fails.

Add a helper which unwinds all the bank creation work previously done
and pass into it the previously allocated threshold banks array for
freeing.

  [ bp: Massage. ]

Fixes: 6458de97fc15 ("x86/mce/amd: Straighten CPU hotplug path")
Co-developed-by: Alviro Iskandar Setiawan <alviro.iskandar@xxxxxxxxxxx>
Signed-off-by: Alviro Iskandar Setiawan <alviro.iskandar@xxxxxxxxxxx>
Co-developed-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>
Signed-off-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>
Signed-off-by: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220329104705.65256-3-ammarfaizi2@xxxxxxxxxxx
---
 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 1940d30..1c87501 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -1294,10 +1294,23 @@ out_free:
 	kfree(bank);
 }
 
+static void __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])
+			continue;
+
+		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;
@@ -1308,13 +1321,7 @@ 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);
+	__threshold_remove_device(bp);
 	return 0;
 }
 
@@ -1351,15 +1358,14 @@ 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) {
+			__threshold_remove_device(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;
 }