[PATCH AUTOSEL 4.19 73/83] atm: he: fix sign-extension overflow on large shift

Sasha Levin
2019-02-13T02:50:59Z

From: Colin Ian King <colin.king@canonical.com>

[ Upstream commit cb12d72b27a6f41325ae23a11033cf5fedfa1b97 ]

Shifting the 1 by exp by an int can lead to sign-extension overlow when
exp is 31 since 1 is an signed int and sign-extending this result to an
unsigned long long will set the upper 32 bits. Fix this by shifting an
unsigned long.

Detected by cppcheck:
(warning) Shifting signed 32-bit value by 31 bits is undefined behaviour

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/atm/he.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/atm/he.c b/drivers/atm/he.c
index 29f102dcfec4..329ce9072ee9 100644
--- a/drivers/atm/he.c
+++ b/drivers/atm/he.c
@@ -717,7 +717,7 @@ static int he_init_cs_block_rcm(struct he_dev *he_dev)
instead of '/ 512', use '>> 9' to prevent a call
to divdu3 on x86 platforms
*/
- rate_cps = (unsigned long long) (1 << exp) * (man + 512) >> 9;
+ rate_cps = (unsigned long long) (1UL << exp) * (man + 512) >> 9;

if (rate_cps < 10)
rate_cps = 10; /* 2.2.1 minimum payload rate is 10 cps */
--
2.19.1