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Commit ce8a3a9e authored by Ben Hutchings's avatar Ben Hutchings Committed by Greg Kroah-Hartman
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staging: android: ashmem: Fix a race condition in pin ioctls 



ashmem_pin_unpin() reads asma->file and asma->size before taking the
ashmem_mutex, so it can race with other operations that modify them.

Build-tested only.

Cc: stable@vger.kernel.org
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 02b7b284

drivers/staging/android/ashmem.c

+11 −8
Original line number Diff line number Diff line
@@ -702,30 +702,32 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, 
	size_t pgstart, pgend;

	int ret = -EINVAL;



	mutex_lock(&ashmem_mutex);



	if (unlikely(!asma->file))

		return -EINVAL;

		goto out_unlock;



	if (unlikely(copy_from_user(&pin, p, sizeof(pin))))

		return -EFAULT;

	if (unlikely(copy_from_user(&pin, p, sizeof(pin)))) {

		ret = -EFAULT;

		goto out_unlock;

	}



	/* per custom, you can pass zero for len to mean "everything onward" */

	if (!pin.len)

		pin.len = PAGE_ALIGN(asma->size) - pin.offset;



	if (unlikely((pin.offset | pin.len) & ~PAGE_MASK))

		return -EINVAL;

		goto out_unlock;



	if (unlikely(((__u32)-1) - pin.offset < pin.len))

		return -EINVAL;

		goto out_unlock;



	if (unlikely(PAGE_ALIGN(asma->size) < pin.offset + pin.len))

		return -EINVAL;

		goto out_unlock;



	pgstart = pin.offset / PAGE_SIZE;

	pgend = pgstart + (pin.len / PAGE_SIZE) - 1;



	mutex_lock(&ashmem_mutex);



	switch (cmd) {

	case ASHMEM_PIN:

		ret = ashmem_pin(asma, pgstart, pgend);
@@ -738,6 +740,7 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, 
		break;

	}



out_unlock:

	mutex_unlock(&ashmem_mutex);



	return ret;