From f53d31162a8dd5994fe44aff0a2d36c7681b9520 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Mon, 23 Mar 2015 17:50:27 +0000 Subject: [PATCH] spi: spidev: fix possible arithmetic overflow for multi-transfer message commit f20fbaad7620af2df36a1f9d1c9ecf48ead5b747 upstream. `spidev_message()` sums the lengths of the individual SPI transfers to determine the overall SPI message length. It restricts the total length, returning an error if too long, but it does not check for arithmetic overflow. For example, if the SPI message consisted of two transfers and the first has a length of 10 and the second has a length of (__u32)(-1), the total length would be seen as 9, even though the second transfer is actually very long. If the second transfer specifies a null `rx_buf` and a non-null `tx_buf`, the `copy_from_user()` could overrun the spidev's pre-allocated tx buffer before it reaches an invalid user memory address. Fix it by checking that neither the total nor the individual transfer lengths exceed the maximum allowed value. Thanks to Dan Carpenter for reporting the potential integer overflow. Signed-off-by: Ian Abbott Signed-off-by: Mark Brown Signed-off-by: Greg Kroah-Hartman --- drivers/spi/spidev.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c index d7c6e36021e8..2fe5b61d886a 100644 --- a/drivers/spi/spidev.c +++ b/drivers/spi/spidev.c @@ -243,7 +243,10 @@ static int spidev_message(struct spidev_data *spidev, k_tmp->len = u_tmp->len; total += k_tmp->len; - if (total > bufsiz) { + /* Check total length of transfers. Also check each + * transfer length to avoid arithmetic overflow. + */ + if (total > bufsiz || k_tmp->len > bufsiz) { status = -EMSGSIZE; goto done; } -- 2.39.5