4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Martin Kelly <mkelly@xxxxxxxx> commit 3d13de4b027d5f6276c0f9d3a264f518747d83f2 upstream. 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: Martin Kelly <mkelly@xxxxxxxx> cc: <Stable@xxxxxxxxxxxxxxx> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/iio/buffer/kfifo_buf.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/drivers/iio/buffer/kfifo_buf.c +++ b/drivers/iio/buffer/kfifo_buf.c @@ -24,6 +24,13 @@ static inline int __iio_allocate_kfifo(s 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); }
