linux-kernel - [PATCH] platform/x86: intel_pmc_core: fix out-of-bounds accesses on stack

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Date:   Thu, 26 Jan 2017 17:27:23 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Rajneesh Bhardwaj <rajneesh.bhardwaj@...el.com>,
        Vishwanath Somayaji <vishwanath.somayaji@...el.com>
CC:     Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        <platform-driver-x86@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>
Subject: [PATCH] platform/x86: intel_pmc_core: fix out-of-bounds accesses on stack

pmc_core_mtpmc_link_status() an pmc_core_check_read_lock_bit() use
test_bit() on local 32-bit variable. This causes out-of-bounds
access since test_bit() expects object at least of 'unsigned long' size:

   BUG: KASAN: stack-out-of-bounds in pmc_core_probe+0x3aa/0x3b0
    Call Trace:
     __asan_report_load_n_noabort+0x5c/0x80
     pmc_core_probe+0x3aa/0x3b0
     local_pci_probe+0xf9/0x1e0
     pci_device_probe+0x27b/0x350
     driver_probe_device+0x419/0x830
     __driver_attach+0x15f/0x1d0
     bus_for_each_dev+0x129/0x1d0
     driver_attach+0x42/0x70
     bus_add_driver+0x385/0x690
     driver_register+0x1a9/0x3d0
     __pci_register_driver+0x1a2/0x290
     intel_pmc_core_driver_init+0x19/0x1b
     do_one_initcall+0x12e/0x280
     kernel_init_freeable+0x57c/0x623
     kernel_init+0x13/0x140
     ret_from_fork+0x2e/0x40

Fix this by open coding bit test. While at it, also refactor this code
a little bit.

Fixes: 173943b3dae5 ("platform/x86: intel_pmc_core: ModPhy core lanes pg status")
Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
---
 drivers/platform/x86/intel_pmc_core.c | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/drivers/platform/x86/intel_pmc_core.c b/drivers/platform/x86/intel_pmc_core.c
index b130b8c..2fb5747 100644
--- a/drivers/platform/x86/intel_pmc_core.c
+++ b/drivers/platform/x86/intel_pmc_core.c
@@ -184,12 +184,8 @@ DEFINE_DEBUGFS_ATTRIBUTE(pmc_core_dev_state, pmc_core_dev_state_get, NULL, "%llu
 
 static int pmc_core_check_read_lock_bit(void)
 {
-	struct pmc_dev *pmcdev = &pmc;
-	u32 value;
-
-	value = pmc_core_reg_read(pmcdev, SPT_PMC_PM_CFG_OFFSET);
-	return test_bit(SPT_PMC_READ_DISABLE_BIT,
-			(unsigned long *)&value);
+	u32 value = pmc_core_reg_read(&pmc, SPT_PMC_PM_CFG_OFFSET);
+	return value & (1U << SPT_PMC_READ_DISABLE_BIT);
 }
 
 #if IS_ENABLED(CONFIG_DEBUG_FS)
@@ -234,12 +230,8 @@ static const struct file_operations pmc_core_ppfear_ops = {
 /* This function should return link status, 0 means ready */
 static int pmc_core_mtpmc_link_status(void)
 {
-	struct pmc_dev *pmcdev = &pmc;
-	u32 value;
-
-	value = pmc_core_reg_read(pmcdev, SPT_PMC_PM_STS_OFFSET);
-	return test_bit(SPT_PMC_MSG_FULL_STS_BIT,
-			(unsigned long *)&value);
+	u32 value = pmc_core_reg_read(&pmc, SPT_PMC_PM_STS_OFFSET);
+	return value & (1U << SPT_PMC_MSG_FULL_STS_BIT);
 }
 
 static int pmc_core_send_msg(u32 *addr_xram)
-- 
2.10.2