[PATCH 1/3] pinctrl: renesas: rzg2l: Fix NULL pointer dereference in rzg2l_dt_subnode_to_map()

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

Fix the below random NULL pointer crash during boot by serializing
pinctrl group and function creation/remove calls in
rzg2l_dt_subnode_to_map() with mutex lock.

Crash logs:
[   15.310036] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[   15.354291] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[   15.870714] [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
[   15.939989] Internal error: Oops: 0000000096000004 2 PREEMPT SMP
[   15.946285] Modules linked in: drm_shmem_helper rzg2l_mipi_dsi videobuf2_common display_connector gpu_sched mc drm_kms_helper rcar_fcp drm rcar_canfd snd_soc_wm8978 rtc_isl1208 can_dev rzg2l_adc snd_soc_rz_ssi renesas_rpc_if spi_rspi backlight ipv6
[   15.969077] CPU: 1 PID: 117 Comm: systemd-udevd Tainted: G      D            6.5.0-rc4-next-20230801-00013-gd1819ab30a54 #986
[   15.980351] Hardware name: Renesas SMARC EVK based on r9a07g054l2 (DT)
[   15.986857] pstate: 40400005 (nZcv daif +PAN UAO -TCO -DIT -SSBS BTYPE=-)
[   15.993797] pc : __pi_strcmp+0x20/0x140
[   15.997647] lr : pinmux_func_name_to_selector+0x68/0xa4
[   16.002876] sp : ffff800082d9b5a0
[   16.006210] x29: ffff800082d9b5a0 x28: 0000000000000002 x27: ffff00000cda7080
[   16.013338] x26: 0000000000000002 x25: ffff00000a1f26c0 x24: ffff00000cda7080
[   16.020456] x23: ffff800081224960 x22: ffff00007fc2e598 x21: 000000000000000c
[   16.027571] x20: ffff00000b6c8840 x19: 000000000000000b x18: 0000000000000002
[   16.034686] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
[   16.041799] x14: 0000000000000001 x13: 0000000000068a68 x12: 0000000000000040
[   16.048913] x11: ffff00000b092ff8 x10: 0000ffff803d1a68 x9 : ffff00000b6c8888
[   16.056028] x8 : 0101010101010101 x7 : 0000000000000000 x6 : 0000000000000000
[   16.063142] x5 : ffff00000b092ff8 x4 : ffff00000b093078 x3 : 0000000000000000
[   16.070256] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff00007fc2e598
[   16.077370] Call trace:
[   16.079807]  __pi_strcmp+0x20/0x140
[   16.083296]  pinmux_generic_add_function+0x34/0xcc
[   16.088077]  rzg2l_dt_subnode_to_map+0x314/0x44c
[   16.092682]  rzg2l_dt_node_to_map+0x164/0x194
[   16.097025]  pinctrl_dt_to_map+0x218/0x37c
[   16.101107]  create_pinctrl+0x70/0x3d8

Fixes: c4c4637eb57f ("pinctrl: renesas: Add RZ/G2L pin and gpio controller driver")
Cc: stable@xxxxxxxxxx
Tested-by: Chris Paterson <Chris.Paterson2@xxxxxxxxxxx>
Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
---
 drivers/pinctrl/renesas/pinctrl-rzg2l.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/pinctrl/renesas/pinctrl-rzg2l.c b/drivers/pinctrl/renesas/pinctrl-rzg2l.c
index 4f34f8f24bde..8a14cbb56449 100644
--- a/drivers/pinctrl/renesas/pinctrl-rzg2l.c
+++ b/drivers/pinctrl/renesas/pinctrl-rzg2l.c
@@ -11,6 +11,7 @@
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/of.h>
 #include <linux/of_irq.h>
 #include <linux/platform_device.h>
@@ -153,6 +154,7 @@ struct rzg2l_pinctrl {
 	unsigned int			hwirq[RZG2L_TINT_MAX_INTERRUPT];
 
 	spinlock_t			lock;
+	struct mutex			mutex; /* serialize adding groups and functions */
 };
 
 static const unsigned int iolh_groupa_mA[] = { 2, 4, 8, 12 };
@@ -362,10 +364,12 @@ static int rzg2l_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;
 	}
 
@@ -380,6 +384,8 @@ static int rzg2l_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;
@@ -391,6 +397,7 @@ static int rzg2l_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);
@@ -1503,6 +1510,7 @@ static int rzg2l_pinctrl_probe(struct platform_device *pdev)
 
 	spin_lock_init(&pctrl->lock);
 	spin_lock_init(&pctrl->bitmap_lock);
+	mutex_init(&pctrl->mutex);
 
 	platform_set_drvdata(pdev, pctrl);
 
-- 
2.25.1