From: Paweł Narewski Date: Wed, 24 Dec 2025 08:26:40 +0000 (+0100) Subject: gpiolib: fix race condition for gdev->srcu X-Git-Tag: v6.19-rc5~23^2~8 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a7ac22d53d0990152b108c3f4fe30df45fcb0181;p=thirdparty%2Flinux.git gpiolib: fix race condition for gdev->srcu 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 Signed-off-by: Paweł Narewski [Bartosz: fixed a build issue, removed stray newline] Link: https://lore.kernel.org/r/20251224082641.10769-1-bartosz.golaszewski@oss.qualcomm.com Signed-off-by: Bartosz Golaszewski --- diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 9ccfb7af67cc..c06152b16dbc 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 @@ err_remove_of_chip: 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 @@ err_remove_from_list: 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: