diff mbox series

[next] mm: selftests: fix potential integer overflow on shift of a int

Message ID 20210526150947.3751728-1-colin.king@canonical.com (mailing list archive)
State New
Headers show
Series [next] mm: selftests: fix potential integer overflow on shift of a int | expand

Commit Message

Colin King May 26, 2021, 3:09 p.m. UTC
From: Colin Ian King <colin.king@canonical.com>

The left shift of the int mapped is evaluated using 32 bit arithmetic
and then assigned to an unsigned long. In the case where mapped is
0x80000 when PAGE_SHIFT is 12 will lead to the upper bits being
sign extended in the unsigned long. Larger values can lead to an
int overflow. Avoid this by casting mapped to unsigned long before
shifting.

Addresses-Coverity: ("Uninitentional integer overflow")
Fixes: 8b2a105c3794 ("mm: selftests for exclusive device memory")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 lib/test_hmm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Jason Gunthorpe May 26, 2021, 4:49 p.m. UTC | #1
On Wed, May 26, 2021 at 04:09:47PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> The left shift of the int mapped is evaluated using 32 bit arithmetic
> and then assigned to an unsigned long. In the case where mapped is
> 0x80000 when PAGE_SHIFT is 12 will lead to the upper bits being
> sign extended in the unsigned long. Larger values can lead to an
> int overflow. Avoid this by casting mapped to unsigned long before
> shifting.
> 
> Addresses-Coverity: ("Uninitentional integer overflow")
> Fixes: 8b2a105c3794 ("mm: selftests for exclusive device memory")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>  lib/test_hmm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/test_hmm.c b/lib/test_hmm.c
> index 74d69f87691e..b54657701b3a 100644
> +++ b/lib/test_hmm.c
> @@ -749,7 +749,7 @@ static int dmirror_exclusive(struct dmirror *dmirror,
>  			}
>  		}
>  
> -		if (addr + (mapped << PAGE_SHIFT) < next) {
> +		if (addr + ((unsigned int)mapped << PAGE_SHIFT) < next) {

Just fix the type for mapped. It started out as an unsigned long in
dmirror_atomic_map() and wrongly became an int here

Jason
diff mbox series

Patch

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index 74d69f87691e..b54657701b3a 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -749,7 +749,7 @@  static int dmirror_exclusive(struct dmirror *dmirror,
 			}
 		}
 
-		if (addr + (mapped << PAGE_SHIFT) < next) {
+		if (addr + ((unsigned int)mapped << PAGE_SHIFT) < next) {
 			mmap_read_unlock(mm);
 			mmput(mm);
 			return -EBUSY;