linux-hardening - [PATCH v2] cpufreq: brcmstb-avs-cpufreq: Fix -Warray-bounds bug

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Message-ID: <ZMgiiEmBORZRaobc@work>
Date:   Mon, 31 Jul 2023 15:07:20 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Markus Mayer <mmayer@...adcom.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Florian Fainelli <florian.fainelli@...adcom.com>
Cc:     linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH v2] cpufreq: brcmstb-avs-cpufreq: Fix -Warray-bounds bug

Update the iteration conditions in the for() loop to avoid writing in
array `table` beyond its allocated size at:

drivers/cpufreq/brcmstb-avs-cpufreq.c:
449         table[i].frequency = CPUFREQ_TABLE_END;

This fixes the following -Warray-bounds warning seen after building
ARM with multi_v7_defconfig (GCC 13):
In function 'brcm_avs_get_freq_table',
    inlined from 'brcm_avs_cpufreq_init' at drivers/cpufreq/brcmstb-avs-cpufreq.c:623:15:
drivers/cpufreq/brcmstb-avs-cpufreq.c:449:28: warning: array subscript 5 is outside array bounds of 'void[60]' [-Warray-bounds=]
  449 |         table[i].frequency = CPUFREQ_TABLE_END;
In file included from include/linux/node.h:18,
                 from include/linux/cpu.h:17,
                 from include/linux/cpufreq.h:12,
                 from drivers/cpufreq/brcmstb-avs-cpufreq.c:44:
In function 'devm_kmalloc_array',
    inlined from 'devm_kcalloc' at include/linux/device.h:328:9,
    inlined from 'brcm_avs_get_freq_table' at drivers/cpufreq/brcmstb-avs-cpufreq.c:437:10,
    inlined from 'brcm_avs_cpufreq_init' at drivers/cpufreq/brcmstb-avs-cpufreq.c:623:15:
include/linux/device.h:323:16: note: at offset 60 into object of size 60 allocated by 'devm_kmalloc'
  323 |         return devm_kmalloc(dev, bytes, flags);
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
routines on memcpy() and help us make progress towards globally
enabling -Warray-bounds.

Link: https://github.com/KSPP/linux/issues/324
Fixes: de322e085995 ("cpufreq: brcmstb-avs-cpufreq: AVS CPUfreq driver for Broadcom STB SoCs")
Cc: stable@...r.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
Changes in v2:
 - Update changelog text. Add more details.

v1:
 - Link: https://lore.kernel.org/linux-hardening/ZMgfWEA0GAN%2FRog8@work/

 drivers/cpufreq/brcmstb-avs-cpufreq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cpufreq/brcmstb-avs-cpufreq.c b/drivers/cpufreq/brcmstb-avs-cpufreq.c
index 1bdd513bcd19..99ba2d707eff 100644
--- a/drivers/cpufreq/brcmstb-avs-cpufreq.c
+++ b/drivers/cpufreq/brcmstb-avs-cpufreq.c
@@ -439,7 +439,7 @@ brcm_avs_get_freq_table(struct device *dev, struct private_data *priv)
 	if (!table)
 		return ERR_PTR(-ENOMEM);
 
-	for (i = AVS_PSTATE_P0; i <= AVS_PSTATE_MAX; i++) {
+	for (i = AVS_PSTATE_P0; i < AVS_PSTATE_MAX; i++) {
 		ret = brcm_avs_set_pstate(priv, i);
 		if (ret)
 			return ERR_PTR(ret);
-- 
2.34.1