[PATCH 2/3] pinctrl: renesas: rzv2m: Fix NULL pointer dereference in rzv2m_dt_subnode_to_map()

[Biju Das <biju.das.jz@xxxxxxxxxxxxxx>]

Fix the below random NULL pointer crash during boot by serializing
groups and functions creation in rzv2m_dt_subnode_to_map() with
mutex lock.

Crash logs:
[ 9.215283] CPU: 0 PID: 104 Comm: systemd-udevd Tainted: G D 6.4.0-next-20230628-g9d42909cfd05-dirty #1
[ 9.226128] Hardware name: RZ/V2M Evaluation Kit 2.0 (DT)
[ 9.231555] pstate: 40000005 (nZcv daif PAN -UAO -TCO -DIT -SSBS BTYPE=-)
[ 9.238557] pc : __pi_strcmp+0x20/0x140
[ 9.242428] lr : pinmux_func_name_to_selector+0x68/0xa4
[ 9.247688] sp : ffff800082c1b630
[ 9.251018] x29: ffff800082c1b630 x28: 0000000000000002 x27: ffff000143ee35c0
[ 9.258201] x26: 0000000000000002 x25: ffff000143ee6100 x24: ffff000143ee35c0
[ 9.265385] x23: ffff80008120ecf8 x22: ffff0001bfab8e88 x21: 0000000000000007
[ 9.272569] x20: ffff0001437ee9c0 x19: 0000000000000006 x18: 0000000000000020
[ 9.279751] x17: 0000000000000000 x16: 0000000000000000 x15: ffffffffffffffff
[ 9.286933] x14: ffffffffffffffff x13: 0000000000000038 x12: 0000000000000040
[ 9.294117] x11: ffff0001430d4db0 x10: 0000fffe40547178 x9 : ffff0001437eea08
[ 9.301300] x8 : 0101010101010101 x7 : 0000000000000000 x6 : 0000000000000000
[ 9.308483] x5 : ffff0001430d4db0 x4 : ffff0001430d4e08 x3 : 0000000000000000
[ 9.315666] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0001bfab8e88
[ 9.322850] Call trace:
[ 9.325308] __pi_strcmp+0x20/0x140
[ 9.328821] pinmux_generic_add_function+0x34/0xcc
[ 9.333643] rzv2m_dt_subnode_to_map+0x2e4/0x418
[ 9.338290] rzv2m_dt_node_to_map+0x15c/0x18c
[ 9.342672] pinctrl_dt_to_map+0x218/0x37c
[ 9.346795] create_pinctrl+0x70/0x3d8

Fixes: 92a9b8252576 ("pinctrl: renesas: Add RZ/V2M pin and gpio controller driver")
Cc: stable@xxxxxxxxxx
Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
---
 drivers/pinctrl/renesas/pinctrl-rzv2m.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/pinctrl/renesas/pinctrl-rzv2m.c b/drivers/pinctrl/renesas/pinctrl-rzv2m.c
index c73784b8b4ba..65718c9bfc0c 100644
--- a/drivers/pinctrl/renesas/pinctrl-rzv2m.c
+++ b/drivers/pinctrl/renesas/pinctrl-rzv2m.c
@@ -14,6 +14,7 @@
 #include <linux/gpio/driver.h>
 #include <linux/io.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/spinlock.h>
@@ -124,6 +125,7 @@ struct rzv2m_pinctrl {
 	struct pinctrl_gpio_range	gpio_range;
 
 	spinlock_t			lock;
+	struct mutex			mutex; /* serialize adding groups and functions */
 };
 
 static const unsigned int drv_1_8V_group2_uA[] = { 1800, 3800, 7800, 11000 };
@@ -322,10 +324,12 @@ static int rzv2m_dt_subnode_to_map(struct pinctrl_dev *pctldev,
 		name = np->name;
 	}
 
+	mutex_lock(&pctrl->mutex);
 	/* Register a single pin group listing all the pins we read from DT */
 	gsel = pinctrl_generic_add_group(pctldev, name, pins, num_pinmux, NULL);
 	if (gsel < 0) {
 		ret = gsel;
+		mutex_unlock(&pctrl->mutex);
 		goto done;
 	}
 
@@ -340,6 +344,8 @@ static int rzv2m_dt_subnode_to_map(struct pinctrl_dev *pctldev,
 		goto remove_group;
 	}
 
+	mutex_unlock(&pctrl->mutex);
+
 	maps[idx].type = PIN_MAP_TYPE_MUX_GROUP;
 	maps[idx].data.mux.group = name;
 	maps[idx].data.mux.function = name;
@@ -351,6 +357,7 @@ static int rzv2m_dt_subnode_to_map(struct pinctrl_dev *pctldev,
 
 remove_group:
 	pinctrl_generic_remove_group(pctldev, gsel);
+	mutex_unlock(&pctrl->mutex);
 done:
 	*index = idx;
 	kfree(configs);
@@ -1065,6 +1072,7 @@ static int rzv2m_pinctrl_probe(struct platform_device *pdev)
 				     "failed to enable GPIO clk\n");
 
 	spin_lock_init(&pctrl->lock);
+	mutex_init(&pctrl->mutex);
 
 	platform_set_drvdata(pdev, pctrl);
 
-- 
2.25.1