atm: zatm: Fix potential Spectre v1

pool can be indirectly controlled by user-space, hence leading to a potential exploitation of the Spectre variant 1 vulnerability. This issue was detected with the help of Smatch: drivers/atm/zatm.c:1491 zatm_ioctl() warn: potential spectre issue 'zatm_dev->pool_info' (local cap) Fix this by sanitizing pool before using it to index zatm_dev->pool_info Notice that given that speculation windows are large, the policy is to kill the speculation on the first load and not worry if it can be completed with a dependent load/store [1]. [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2 Signed-off-by: Gustavo A. R. Silva <[email protected]> Signed-off-by: David S. Miller <[email protected]>
Owersun · Jun 30, 2018 · ced9e19 · ced9e19
1 parent c7f653e
commit ced9e19
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/drivers/atm/zatm.c b/drivers/atm/zatm.c
@@ -1483,6 +1483,8 @@ static int zatm_ioctl(struct atm_dev *dev,unsigned int cmd,void __user *arg)
 					return -EFAULT;
 				if (pool < 0 || pool > ZATM_LAST_POOL)
 					return -EINVAL;
+				pool = array_index_nospec(pool,
+							  ZATM_LAST_POOL + 1);
 				if (copy_from_user(&info,
 				    &((struct zatm_pool_req __user *) arg)->info,
 				    sizeof(info))) return -EFAULT;