[PATCH v4] platform/x86: intel_pmc_ipc: fix ACPI buffer memory leak

[yongxin.liu@windriver.com]

From: Yongxin Liu <yongxin.liu@windriver.com>

The intel_pmc_ipc() function uses ACPI_ALLOCATE_BUFFER to allocate memory
for the ACPI evaluation result but never frees it, causing a 192-byte
memory leak on each call.

This leak is triggered during network interface initialization when the
stmmac driver calls intel_mac_finish() -> intel_pmc_ipc().

  unreferenced object 0xffff96a848d6ea80 (size 192):
    comm "dhcpcd", pid 541, jiffies 4294684345
    hex dump (first 32 bytes):
      04 00 00 00 05 00 00 00 98 ea d6 48 a8 96 ff ff  ...........H....
      00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
    backtrace (crc b1564374):
      kmemleak_alloc+0x2d/0x40
      __kmalloc_noprof+0x2fa/0x730
      acpi_ut_initialize_buffer+0x83/0xc0
      acpi_evaluate_object+0x29a/0x2f0
      intel_pmc_ipc+0xfd/0x170
      intel_mac_finish+0x168/0x230
      stmmac_mac_finish+0x3d/0x50
      phylink_major_config+0x22b/0x5b0
      phylink_mac_initial_config.constprop.0+0xf1/0x1b0
      phylink_start+0x8e/0x210
      __stmmac_open+0x12c/0x2b0
      stmmac_open+0x23c/0x380
      __dev_open+0x11d/0x2c0
      __dev_change_flags+0x1d2/0x250
      netif_change_flags+0x2b/0x70
      dev_change_flags+0x40/0xb0

Add __free(kfree) for ACPI object to properly release the allocated buffer.

Cc: stable@vger.kernel.org
Fixes: 7e2f7e25f6ff ("arch: x86: add IPC mailbox accessor function and add SoC register access")
Signed-off-by: Yongxin Liu <yongxin.liu@windriver.com>
---
V3->V4:
Move declaration of *obj to where it gets assigned.

V2->V3:
Use __free(kfree) instead of goto and kfree();

V1->V2:
Cover all potential paths for kfree();
---
 include/linux/platform_data/x86/intel_pmc_ipc.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/platform_data/x86/intel_pmc_ipc.h b/include/linux/platform_data/x86/intel_pmc_ipc.h
index 1d34435b7001..85ea381e4a27 100644
--- a/include/linux/platform_data/x86/intel_pmc_ipc.h
+++ b/include/linux/platform_data/x86/intel_pmc_ipc.h
@@ -9,6 +9,7 @@
 #ifndef INTEL_PMC_IPC_H
 #define INTEL_PMC_IPC_H
 #include <linux/acpi.h>
+#include <linux/cleanup.h>
 
 #define IPC_SOC_REGISTER_ACCESS			0xAA
 #define IPC_SOC_SUB_CMD_READ			0x00
@@ -48,7 +49,6 @@ static inline int intel_pmc_ipc(struct pmc_ipc_cmd *ipc_cmd, struct pmc_ipc_rbuf
 		{.type = ACPI_TYPE_INTEGER,},
 	};
 	struct acpi_object_list arg_list = { PMC_IPCS_PARAM_COUNT, params };
-	union acpi_object *obj;
 	int status;
 
 	if (!ipc_cmd || !rbuf)
@@ -72,7 +72,7 @@ static inline int intel_pmc_ipc(struct pmc_ipc_cmd *ipc_cmd, struct pmc_ipc_rbuf
 	if (ACPI_FAILURE(status))
 		return -ENODEV;
 
-	obj = buffer.pointer;
+	union acpi_object *obj __free(kfree) = buffer.pointer;
 
 	if (obj && obj->type == ACPI_TYPE_PACKAGE &&
 	    obj->package.count == VALID_IPC_RESPONSE) {
-- 
2.46.2