Struct gpio_device now provides a revocable provider to the underlying struct gpio_chip. Leverage revocable for accessing the struct gpio_chip.
Signed-off-by: Tzung-Bi Shih <[email protected]> --- v3: - Change revocable API usages accordingly. v2: https://lore.kernel.org/all/[email protected] - Change usages accordingly after applying https://lore.kernel.org/all/[email protected]. - Preserve a local storage for `struct revocable`. - Combine multiple patches (see "v1:"). - Fix a race condition reported in https://lore.kernel.org/all/CAMRc=mcdaipt85ohm0mkslkuf6e79dy1unsqqbcjnoqtus8...@mail.gmail.com/ and analyzed in https://lore.kernel.org/all/aXEEUWwkxHZzCnaI@tzungbi-laptop/. In v1, the blocking_notifier_chain_unregister() will be skipped if the chip has been removed, leading an UAF in gpiolib_cdev_unregister(). In v2, it won't skip blocking_notifier_chain_unregister(). v1: - https://lore.kernel.org/all/[email protected] - https://lore.kernel.org/all/[email protected] - https://lore.kernel.org/all/[email protected] - https://lore.kernel.org/all/[email protected] - https://lore.kernel.org/all/[email protected] drivers/gpio/gpiolib-cdev.c | 68 ++++++++++++++----------------------- 1 file changed, 26 insertions(+), 42 deletions(-) diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c index 2e3484a89a3b..b491e2737ef2 100644 --- a/drivers/gpio/gpiolib-cdev.c +++ b/drivers/gpio/gpiolib-cdev.c @@ -22,6 +22,7 @@ #include <linux/overflow.h> #include <linux/pinctrl/consumer.h> #include <linux/poll.h> +#include <linux/revocable.h> #include <linux/seq_file.h> #include <linux/spinlock.h> #include <linux/string.h> @@ -210,11 +211,9 @@ static long linehandle_ioctl(struct file *file, unsigned int cmd, DECLARE_BITMAP(vals, GPIOHANDLES_MAX); unsigned int i; int ret; + struct gpio_chip *gc; - guard(srcu)(&lh->gdev->srcu); - - if (!rcu_access_pointer(lh->gdev->chip)) - return -ENODEV; + revocable_try_access_or_return(lh->gdev->chip_rp, gc); switch (cmd) { case GPIOHANDLE_GET_LINE_VALUES_IOCTL: @@ -1432,11 +1431,9 @@ static long linereq_ioctl(struct file *file, unsigned int cmd, { struct linereq *lr = file->private_data; void __user *ip = (void __user *)arg; + struct gpio_chip *gc; - guard(srcu)(&lr->gdev->srcu); - - if (!rcu_access_pointer(lr->gdev->chip)) - return -ENODEV; + revocable_try_access_or_return(lr->gdev->chip_rp, gc); switch (cmd) { case GPIO_V2_LINE_GET_VALUES_IOCTL: @@ -1463,10 +1460,10 @@ static __poll_t linereq_poll(struct file *file, { struct linereq *lr = file->private_data; __poll_t events = 0; + struct gpio_chip *gc; - guard(srcu)(&lr->gdev->srcu); - - if (!rcu_access_pointer(lr->gdev->chip)) + revocable_try_access_with(lr->gdev->chip_rp, gc); + if (!gc) return EPOLLHUP | EPOLLERR; poll_wait(file, &lr->wait, wait); @@ -1485,11 +1482,9 @@ static ssize_t linereq_read(struct file *file, char __user *buf, struct gpio_v2_line_event le; ssize_t bytes_read = 0; int ret; + struct gpio_chip *gc; - guard(srcu)(&lr->gdev->srcu); - - if (!rcu_access_pointer(lr->gdev->chip)) - return -ENODEV; + revocable_try_access_or_return(lr->gdev->chip_rp, gc); if (count < sizeof(le)) return -EINVAL; @@ -1781,10 +1776,10 @@ static __poll_t lineevent_poll(struct file *file, { struct lineevent_state *le = file->private_data; __poll_t events = 0; + struct gpio_chip *gc; - guard(srcu)(&le->gdev->srcu); - - if (!rcu_access_pointer(le->gdev->chip)) + revocable_try_access_with(le->gdev->chip_rp, gc); + if (!gc) return EPOLLHUP | EPOLLERR; poll_wait(file, &le->wait, wait); @@ -1819,11 +1814,9 @@ static ssize_t lineevent_read(struct file *file, char __user *buf, ssize_t bytes_read = 0; ssize_t ge_size; int ret; + struct gpio_chip *gc; - guard(srcu)(&le->gdev->srcu); - - if (!rcu_access_pointer(le->gdev->chip)) - return -ENODEV; + revocable_try_access_or_return(le->gdev->chip_rp, gc); /* * When compatible system call is being used the struct gpioevent_data, @@ -1901,11 +1894,9 @@ static long lineevent_ioctl(struct file *file, unsigned int cmd, struct lineevent_state *le = file->private_data; void __user *ip = (void __user *)arg; struct gpiohandle_data ghd; + struct gpio_chip *gc; - guard(srcu)(&le->gdev->srcu); - - if (!rcu_access_pointer(le->gdev->chip)) - return -ENODEV; + revocable_try_access_or_return(le->gdev->chip_rp, gc); /* * We can get the value for an event line but not set it, @@ -2434,12 +2425,10 @@ static long gpio_ioctl(struct file *file, unsigned int cmd, unsigned long arg) struct gpio_chardev_data *cdev = file->private_data; struct gpio_device *gdev = cdev->gdev; void __user *ip = (void __user *)arg; - - guard(srcu)(&gdev->srcu); + struct gpio_chip *gc; /* We fail any subsequent ioctl():s when the chip is gone */ - if (!rcu_access_pointer(gdev->chip)) - return -ENODEV; + revocable_try_access_or_return(gdev->chip_rp, gc); /* Fill in the struct and pass to userspace */ switch (cmd) { @@ -2497,12 +2486,9 @@ static void lineinfo_changed_func(struct work_struct *work) * Pin functions are in general much more static and while it's * not 100% bullet-proof, it's good enough for most cases. */ - scoped_guard(srcu, &ctx->gdev->srcu) { - gc = srcu_dereference(ctx->gdev->chip, &ctx->gdev->srcu); - if (gc && - !pinctrl_gpio_can_use_line(gc, ctx->chg.info.offset)) + revocable_try_access_with_scoped(ctx->gdev->chip_rp, gc) + if (!pinctrl_gpio_can_use_line(gc, ctx->chg.info.offset)) ctx->chg.info.flags |= GPIO_V2_LINE_FLAG_USED; - } } ret = kfifo_in_spinlocked(&ctx->cdev->events, &ctx->chg, 1, @@ -2583,10 +2569,10 @@ static __poll_t lineinfo_watch_poll(struct file *file, { struct gpio_chardev_data *cdev = file->private_data; __poll_t events = 0; + struct gpio_chip *gc; - guard(srcu)(&cdev->gdev->srcu); - - if (!rcu_access_pointer(cdev->gdev->chip)) + revocable_try_access_with(cdev->gdev->chip_rp, gc); + if (!gc) return EPOLLHUP | EPOLLERR; poll_wait(file, &cdev->wait, pollt); @@ -2606,11 +2592,9 @@ static ssize_t lineinfo_watch_read(struct file *file, char __user *buf, ssize_t bytes_read = 0; int ret; size_t event_size; + struct gpio_chip *gc; - guard(srcu)(&cdev->gdev->srcu); - - if (!rcu_access_pointer(cdev->gdev->chip)) - return -ENODEV; + revocable_try_access_or_return(cdev->gdev->chip_rp, gc); #ifndef CONFIG_GPIO_CDEV_V1 event_size = sizeof(struct gpio_v2_line_info_changed); -- 2.53.0.310.g728cabbaf7-goog
