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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Yanjiang Jin <yanjiang.jin@hxt-semitech.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 067/110] pinctrl: core: make sure strcmp() doesnt get a null parameter
Date:   Thu, 18 Apr 2019 19:56:56 +0200
Message-Id: <20190418160444.716957105@linuxfoundation.org>
In-Reply-To: <20190418160437.484158340@linuxfoundation.org>
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[ Upstream commit 54a58185bfafb5af5045fb8388c45daa373f90f3 ]

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>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 a3dd777e3ce8..c6ff4d5fa482 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,
-- 
2.19.1