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From:   Yanjiang Jin <yanjiang.jin@hxt-semitech.com>
To:     <jinyanjiang@gmail.com>, <linus.walleij@linaro.org>
CC:     <yanjiang.jin@hxt-semitech.com>, <yu.zheng@hxt-semitech.com>,
        <linux-gpio@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: [PATCH] pinctrl: core: make sure strcmp() doesn't get a null parameter
Date:   Sat, 29 Sep 2018 17:06:55 +0800
Message-ID: <1538212015-10374-2-git-send-email-yanjiang.jin@hxt-semitech.com>
In-Reply-To: <1538212015-10374-1-git-send-email-yanjiang.jin@hxt-semitech.com>
References: <1538212015-10374-1-git-send-email-yanjiang.jin@hxt-semitech.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Some drivers, for example, QCOM's qdf2xxx, set groups[gpio].name only
when gpio is valid, and leave invalid gpio names as null.
If we want to access the sys node "pinconf-groups",
pinctrl_get_group_selector() -> get_group_name() may return a null
pointer if group_selector is invalid, then the below Kernel panic
would happen since strcmp() uses this null pointer to do comparison.

 Unable to handle kernel NULL pointer dereference at ss 00000000
el:Internal error: Oops: 9600000[ 143.080279]
SMP
 CPU: 19 PID: 2493 Comm: read_all Tainted: G O
.aarch64 #1
 Hardware name: HXT Semiconductor HXT REP-2 System
 PC is at strcmp+0x18/0x154
 LR is at pinctrl_get_group_selector+0x6c/0xe8
 Process read_all (pid: 2493, stack limit =
 Call trace:
 Exception stack
  strcmp+0x18/0x154
  pin_config_group_get+0x64/0xd8
  pinconf_generic_dump_one+0xd8/0x1c0
  pinconf_generic_dump_pins+0x94/0xc8
  pinconf_groups_show+0xb4/0x104
  seq_read+0x178/0x464
  full_proxy_read+0x6c/0xac
  __vfs_read+0x58/0x178
  vfs_read+0x94/0x164
  SyS_read+0x60/0xc0
  __sys_trace_return+0x0/0x4
 --[ end trace]--
 Kernel panic - not syncing: Fatal exception

Signed-off-by: Yanjiang Jin <yanjiang.jin@hxt-semitech.com>
---
 drivers/pinctrl/core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index a3dd777..c6ff4d5 100644
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -627,7 +627,7 @@ static int pinctrl_generic_group_name_to_selector(struct pinctrl_dev *pctldev,
        while (selector < ngroups) {
                const char *gname = ops->get_group_name(pctldev, selector);

-               if (!strcmp(function, gname))
+               if (gname && !strcmp(function, gname))
                        return selector;

                selector++;
@@ -743,7 +743,7 @@ int pinctrl_get_group_selector(struct pinctrl_dev *pctldev,
        while (group_selector < ngroups) {
                const char *gname = pctlops->get_group_name(pctldev,
                                                            group_selector);
-               if (!strcmp(gname, pin_group)) {
+               if (gname && !strcmp(gname, pin_group)) {
                        dev_dbg(pctldev->dev,
                                "found group selector %u for %s\n",
                                group_selector,
--
1.8.3.1


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