Commit 3d13de4b authored by Martin Kelly's avatar Martin Kelly Committed by Jonathan Cameron

iio:kfifo_buf: check for uint overflow

Currently, the following causes a kernel OOPS in memcpy:

echo 1073741825 > buffer/length
echo 1 > buffer/enable

Note that using 1073741824 instead of 1073741825 causes "write error:
Cannot allocate memory" but no OOPS.

This is because 1073741824 == 2^30 and 1073741825 == 2^30+1. Since kfifo
rounds up to the nearest power of 2, it will actually call kmalloc with
roundup_pow_of_two(length) * bytes_per_datum.

Using length == 1073741825 and bytes_per_datum == 2, we get:

kmalloc(roundup_pow_of_two(1073741825) * 2
or kmalloc(2147483648 * 2)
or kmalloc(4294967296)
or kmalloc(UINT_MAX + 1)

so this overflows to 0, causing kmalloc to return ZERO_SIZE_PTR and
subsequent memcpy to fail once the device is enabled.

Fix this by checking for overflow prior to allocating a kfifo. With this
check added, the above code returns -EINVAL when enabling the buffer,
rather than causing an OOPS.
Signed-off-by: default avatarMartin Kelly <mkelly@xevo.com>
cc: <Stable@vger.kernel.org>
Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
parent c043ec1c
......@@ -27,6 +27,13 @@ static inline int __iio_allocate_kfifo(struct iio_kfifo *buf,
if ((length == 0) || (bytes_per_datum == 0))
return -EINVAL;
/*
* Make sure we don't overflow an unsigned int after kfifo rounds up to
* the next power of 2.
*/
if (roundup_pow_of_two(length) > UINT_MAX / bytes_per_datum)
return -EINVAL;
return __kfifo_alloc((struct __kfifo *)&buf->kf, length,
bytes_per_datum, GFP_KERNEL);
}
......
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