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Message-ID: <20251224082641.10769-1-bartosz.golaszewski@oss.qualcomm.com>
Date: Wed, 24 Dec 2025 09:26:40 +0100
From: Bartosz Golaszewski <bartosz.golaszewski@....qualcomm.com>
To: Linus Walleij <linusw@...nel.org>, Bartosz Golaszewski <brgl@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
Paweł Narewski <pawel.narewski@...ia.com>,
Jakub Lewalski <jakub.lewalski@...ia.com>,
Bartosz Golaszewski <bartosz.golaszewski@....qualcomm.com>
Subject: [PATCH v2] gpiolib: fix race condition for gdev->srcu
From: Paweł Narewski <pawel.narewski@...ia.com>
If two drivers were calling gpiochip_add_data_with_key(), one may be
traversing the srcu-protected list in gpio_name_to_desc(), meanwhile
other has just added its gdev in gpiodev_add_to_list_unlocked().
This creates a non-mutexed and non-protected timeframe, when one
instance is dereferencing and using &gdev->srcu, before the other
has initialized it, resulting in crash:
[ 4.935481] Unable to handle kernel paging request at virtual address ffff800272bcc000
[ 4.943396] Mem abort info:
[ 4.943400] ESR = 0x0000000096000005
[ 4.943403] EC = 0x25: DABT (current EL), IL = 32 bits
[ 4.943407] SET = 0, FnV = 0
[ 4.943410] EA = 0, S1PTW = 0
[ 4.943413] FSC = 0x05: level 1 translation fault
[ 4.943416] Data abort info:
[ 4.943418] ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000
[ 4.946220] CM = 0, WnR = 0, TnD = 0, TagAccess = 0
[ 4.955261] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[ 4.955268] swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000038e6c000
[ 4.961449] [ffff800272bcc000] pgd=0000000000000000
[ 4.969203] , p4d=1000000039739003
[ 4.979730] , pud=0000000000000000
[ 4.980210] phandle (CPU): 0x0000005e, phandle (BE): 0x5e000000 for node "reset"
[ 4.991736] Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
...
[ 5.121359] pc : __srcu_read_lock+0x44/0x98
[ 5.131091] lr : gpio_name_to_desc+0x60/0x1a0
[ 5.153671] sp : ffff8000833bb430
[ 5.298440]
[ 5.298443] Call trace:
[ 5.298445] __srcu_read_lock+0x44/0x98
[ 5.309484] gpio_name_to_desc+0x60/0x1a0
[ 5.320692] gpiochip_add_data_with_key+0x488/0xf00
5.946419] ---[ end trace 0000000000000000 ]---
Move initialization code for gdev fields before it is added to
gpio_devices, with adjacent initialization code.
Adjust goto statements to reflect modified order of operations
Fixes: 47d8b4c1d868 ("gpio: add SRCU infrastructure to struct gpio_device")
Reviewed-by: Jakub Lewalski <jakub.lewalski@...ia.com>
Signed-off-by: Paweł Narewski <pawel.narewski@...ia.com>
[Bartosz: fixed a build issue, removed stray newline]
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@....qualcomm.com>
---
Changes in v2:
- Use the correct interface to initialize the raw notifier
- Remove stray newline
drivers/gpio/gpiolib.c | 40 ++++++++++++++++++++--------------------
1 file changed, 20 insertions(+), 20 deletions(-)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 409c2f415251..f834b324c247 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1105,6 +1105,18 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
gdev->ngpio = gc->ngpio;
gdev->can_sleep = gc->can_sleep;
+ rwlock_init(&gdev->line_state_lock);
+ RAW_INIT_NOTIFIER_HEAD(&gdev->line_state_notifier);
+ BLOCKING_INIT_NOTIFIER_HEAD(&gdev->device_notifier);
+
+ ret = init_srcu_struct(&gdev->srcu);
+ if (ret)
+ goto err_free_label;
+
+ ret = init_srcu_struct(&gdev->desc_srcu);
+ if (ret)
+ goto err_cleanup_gdev_srcu;
+
scoped_guard(mutex, &gpio_devices_lock) {
/*
* TODO: this allocates a Linux GPIO number base in the global
@@ -1119,7 +1131,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
if (base < 0) {
ret = base;
base = 0;
- goto err_free_label;
+ goto err_cleanup_desc_srcu;
}
/*
@@ -1139,22 +1151,10 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
ret = gpiodev_add_to_list_unlocked(gdev);
if (ret) {
gpiochip_err(gc, "GPIO integer space overlap, cannot add chip\n");
- goto err_free_label;
+ goto err_cleanup_desc_srcu;
}
}
- rwlock_init(&gdev->line_state_lock);
- RAW_INIT_NOTIFIER_HEAD(&gdev->line_state_notifier);
- BLOCKING_INIT_NOTIFIER_HEAD(&gdev->device_notifier);
-
- ret = init_srcu_struct(&gdev->srcu);
- if (ret)
- goto err_remove_from_list;
-
- ret = init_srcu_struct(&gdev->desc_srcu);
- if (ret)
- goto err_cleanup_gdev_srcu;
-
#ifdef CONFIG_PINCTRL
INIT_LIST_HEAD(&gdev->pin_ranges);
#endif
@@ -1164,11 +1164,11 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
ret = gpiochip_set_names(gc);
if (ret)
- goto err_cleanup_desc_srcu;
+ goto err_remove_from_list;
ret = gpiochip_init_valid_mask(gc);
if (ret)
- goto err_cleanup_desc_srcu;
+ goto err_remove_from_list;
for (desc_index = 0; desc_index < gc->ngpio; desc_index++) {
struct gpio_desc *desc = &gdev->descs[desc_index];
@@ -1248,10 +1248,6 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
of_gpiochip_remove(gc);
err_free_valid_mask:
gpiochip_free_valid_mask(gc);
-err_cleanup_desc_srcu:
- cleanup_srcu_struct(&gdev->desc_srcu);
-err_cleanup_gdev_srcu:
- cleanup_srcu_struct(&gdev->srcu);
err_remove_from_list:
scoped_guard(mutex, &gpio_devices_lock)
list_del_rcu(&gdev->list);
@@ -1261,6 +1257,10 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
gpio_device_put(gdev);
goto err_print_message;
}
+err_cleanup_desc_srcu:
+ cleanup_srcu_struct(&gdev->desc_srcu);
+err_cleanup_gdev_srcu:
+ cleanup_srcu_struct(&gdev->srcu);
err_free_label:
kfree_const(gdev->label);
err_free_descs:
--
2.47.3
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