In an effort to separate intentional arithmetic wrap-around from unexpected wrap-around, we need to refactor places that depend on this kind of math. One of the most common code patterns of this is: VAR + value < VAR Notably, this is considered "undefined behavior" for signed and pointer types, which the kernel works around by using the -fno-strict-overflow option in the build[1] (which used to just be -fwrapv). Regardless, we want to get the kernel source to the position where we can meaningfully instrument arithmetic wrap-around conditions and catch them when they are unexpected, regardless of whether they are signed[2], unsigned[3], or pointer[4] types. Refactor open-coded wrap-around addition test to use add_would_overflow(). This paves the way to enabling the wrap-around sanitizers in the future. Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] Link: https://github.com/KSPP/linux/issues/26 [2] Link: https://github.com/KSPP/linux/issues/27 [3] Link: https://github.com/KSPP/linux/issues/344 [4] Cc: Brian Norris <briannorris@xxxxxxxxxxxx> Cc: Kalle Valo <kvalo@xxxxxxxxxx> Cc: "Jonas Dreßler" <verdre@xxxxxxx> Cc: Dmitry Antipov <dmantipov@xxxxxxxxx> Cc: Tsuchiya Yuto <kitakar@xxxxxxxxx> Cc: linux-wireless@xxxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- drivers/net/wireless/marvell/mwifiex/pcie.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/net/wireless/marvell/mwifiex/pcie.c b/drivers/net/wireless/marvell/mwifiex/pcie.c index 5f997becdbaa..e69347e65f0e 100644 --- a/drivers/net/wireless/marvell/mwifiex/pcie.c +++ b/drivers/net/wireless/marvell/mwifiex/pcie.c @@ -2086,7 +2086,7 @@ static int mwifiex_extract_wifi_fw(struct mwifiex_adapter *adapter, switch (dnld_cmd) { case MWIFIEX_FW_DNLD_CMD_1: - if (offset + data_len < data_len) { + if (add_would_overflow(data_len, offset)) { mwifiex_dbg(adapter, ERROR, "bad FW parse\n"); ret = -1; goto done; @@ -2110,7 +2110,7 @@ static int mwifiex_extract_wifi_fw(struct mwifiex_adapter *adapter, case MWIFIEX_FW_DNLD_CMD_5: first_cmd = true; /* Check for integer overflow */ - if (offset + data_len < data_len) { + if (add_would_overflow(data_len, offset)) { mwifiex_dbg(adapter, ERROR, "bad FW parse\n"); ret = -1; goto done; @@ -2120,7 +2120,7 @@ static int mwifiex_extract_wifi_fw(struct mwifiex_adapter *adapter, case MWIFIEX_FW_DNLD_CMD_6: first_cmd = true; /* Check for integer overflow */ - if (offset + data_len < data_len) { + if (add_would_overflow(data_len, offset)) { mwifiex_dbg(adapter, ERROR, "bad FW parse\n"); ret = -1; goto done; -- 2.34.1
