diff options
| author | William Breathitt Gray | 2021-10-21 19:35:40 +0900 |
|---|---|---|
| committer | Greg Kroah-Hartman | 2021-10-21 13:02:47 +0200 |
| commit | 8ac33b8b6841e99a624ace543d92cbf598a91381 (patch) | |
| tree | bfbb42f1f6f41bc9fb8cae0098746d382196ad67 /drivers/counter | |
| parent | 310e75c72fefa3b0b4535f669c8b37c963a2dba5 (diff) | |
counter: Fix use-after-free race condition for events_queue_size write
A race condition is possible when writing to events_queue_size where the
events kfifo is freed during the execution of a kfifo_in(), resulting in
a use-after-free. This patch prevents such a scenario by protecting the
events queue in operation with a spinlock and locking before performing
the events queue size adjustment.
The existing events_lock mutex is renamed to events_out_lock to reflect
that it only protects events queue out operations. Because the events
queue in operations can occur in an interrupt context, a new
events_in_lock spinlock is introduced and utilized.
Fixes: feff17a550c7 ("counter: Implement events_queue_size sysfs attribute")
Cc: David Lechner <david@lechnology.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Link: https://lore.kernel.org/r/20211021103540.955639-1-vilhelm.gray@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/counter')
| -rw-r--r-- | drivers/counter/counter-chrdev.c | 10 | ||||
| -rw-r--r-- | drivers/counter/counter-sysfs.c | 7 |
2 files changed, 13 insertions, 4 deletions
diff --git a/drivers/counter/counter-chrdev.c b/drivers/counter/counter-chrdev.c index 0c82613582f1..b7c62f957a6a 100644 --- a/drivers/counter/counter-chrdev.c +++ b/drivers/counter/counter-chrdev.c @@ -81,10 +81,10 @@ static ssize_t counter_chrdev_read(struct file *filp, char __user *buf, return -ENODEV; } - if (mutex_lock_interruptible(&counter->events_lock)) + if (mutex_lock_interruptible(&counter->events_out_lock)) return -ERESTARTSYS; err = kfifo_to_user(&counter->events, buf, len, &copied); - mutex_unlock(&counter->events_lock); + mutex_unlock(&counter->events_out_lock); if (err < 0) return err; } while (!copied); @@ -436,7 +436,8 @@ int counter_chrdev_add(struct counter_device *const counter) spin_lock_init(&counter->events_list_lock); mutex_init(&counter->n_events_list_lock); init_waitqueue_head(&counter->events_wait); - mutex_init(&counter->events_lock); + spin_lock_init(&counter->events_in_lock); + mutex_init(&counter->events_out_lock); /* Initialize character device */ cdev_init(&counter->chrdev, &counter_fops); @@ -559,7 +560,8 @@ void counter_push_event(struct counter_device *const counter, const u8 event, ev.watch.component = comp_node->component; ev.status = -counter_get_data(counter, comp_node, &ev.value); - copied += kfifo_in(&counter->events, &ev, 1); + copied += kfifo_in_spinlocked_noirqsave(&counter->events, &ev, + 1, &counter->events_in_lock); } exit_early: diff --git a/drivers/counter/counter-sysfs.c b/drivers/counter/counter-sysfs.c index 67a988851657..7cc4d1d523ea 100644 --- a/drivers/counter/counter-sysfs.c +++ b/drivers/counter/counter-sysfs.c @@ -11,6 +11,8 @@ #include <linux/kfifo.h> #include <linux/kstrtox.h> #include <linux/list.h> +#include <linux/mutex.h> +#include <linux/spinlock.h> #include <linux/string.h> #include <linux/sysfs.h> #include <linux/types.h> @@ -796,6 +798,7 @@ static int counter_events_queue_size_write(struct counter_device *counter, { DECLARE_KFIFO_PTR(events, struct counter_event); int err; + unsigned long flags; /* Allocate new events queue */ err = kfifo_alloc(&events, val, GFP_KERNEL); @@ -803,8 +806,12 @@ static int counter_events_queue_size_write(struct counter_device *counter, return err; /* Swap in new events queue */ + mutex_lock(&counter->events_out_lock); + spin_lock_irqsave(&counter->events_in_lock, flags); kfifo_free(&counter->events); counter->events.kfifo = events.kfifo; + spin_unlock_irqrestore(&counter->events_in_lock, flags); + mutex_unlock(&counter->events_out_lock); return 0; } |