[PATCH][net-next] net/mlx4: Use array_size() helper in copy_to_user()

Use array_size() helper instead of the open-coded version in
copy_to_user(). These sorts of multiplication factors need
to be wrapped in array_size().

Link: https://github.com/KSPP/linux/issues/160
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 drivers/net/ethernet/mellanox/mlx4/cq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/cq.c b/drivers/net/ethernet/mellanox/mlx4/cq.c
index f7053a74e6a8..4d4f9cf9facb 100644
--- a/drivers/net/ethernet/mellanox/mlx4/cq.c
+++ b/drivers/net/ethernet/mellanox/mlx4/cq.c

@@ -314,7 +314,8 @@ static int mlx4_init_user_cqes(void *buf, int entries, int cqe_size)
 			buf += PAGE_SIZE;
 		}
 	} else {
-		err = copy_to_user((void __user *)buf, init_ents, entries * cqe_size) ?
+		err = copy_to_user((void __user *)buf, init_ents,
+				   array_size(entries, cqe_size)) ?
 			-EFAULT : 0;
 	}
 

-- 
2.27.0

On 9/28/2021 11:17 PM, Gustavo A. R. Silva wrote:

Thanks for your patch.
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>

On 9/29/21 3:24 AM, Tariq Toukan wrote:

On 9/28/2021 11:17 PM, Gustavo A. R. Silva wrote:

quoted

Use array_size() helper instead of the open-coded version in
copy_to_user(). These sorts of multiplication factors need
to be wrapped in array_size().

Link: https://github.com/KSPP/linux/issues/160
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
  drivers/net/ethernet/mellanox/mlx4/cq.c | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/cq.c b/drivers/net/ethernet/mellanox/mlx4/cq.c
index f7053a74e6a8..4d4f9cf9facb 100644
--- a/drivers/net/ethernet/mellanox/mlx4/cq.c
+++ b/drivers/net/ethernet/mellanox/mlx4/cq.c

@@ -314,7 +314,8 @@ static int mlx4_init_user_cqes(void *buf, int entries, int cqe_size)

              buf += PAGE_SIZE;
          }
      } else {
-        err = copy_to_user((void __user *)buf, init_ents, entries * cqe_size) ?
+        err = copy_to_user((void __user *)buf, init_ents,
+                   array_size(entries, cqe_size)) ?
              -EFAULT : 0;
      }
 

Thanks for your patch.
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>

Not sure why avoiding size_t overflows would make this code safer.
init_ents contains PAGE_SIZE bytes...

BTW

Is @entries guaranteed to be a power of two ?

This function seems to either copy one chunk ( <= PAGE_SIZE),
or a number of full pages.

On 9/29/2021 8:21 PM, Eric Dumazet wrote:

On 9/29/21 3:24 AM, Tariq Toukan wrote:

quoted

On 9/28/2021 11:17 PM, Gustavo A. R. Silva wrote:

quoted

Use array_size() helper instead of the open-coded version in
copy_to_user(). These sorts of multiplication factors need
to be wrapped in array_size().

Link: https://github.com/KSPP/linux/issues/160
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
   drivers/net/ethernet/mellanox/mlx4/cq.c | 3 ++-
   1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/cq.c b/drivers/net/ethernet/mellanox/mlx4/cq.c
index f7053a74e6a8..4d4f9cf9facb 100644
--- a/drivers/net/ethernet/mellanox/mlx4/cq.c
+++ b/drivers/net/ethernet/mellanox/mlx4/cq.c

@@ -314,7 +314,8 @@ static int mlx4_init_user_cqes(void *buf, int entries, int cqe_size)
               buf += PAGE_SIZE;
           }
       } else {
-        err = copy_to_user((void __user *)buf, init_ents, entries * cqe_size) ?
+        err = copy_to_user((void __user *)buf, init_ents,
+                   array_size(entries, cqe_size)) ?
               -EFAULT : 0;
       }
  

Thanks for your patch.
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>

Not sure why avoiding size_t overflows would make this code safer.
init_ents contains PAGE_SIZE bytes...

BTW

Is @entries guaranteed to be a power of two ?

Yes.

This function seems to either copy one chunk ( <= PAGE_SIZE),
or a number of full pages.

Exactly. No remainder handling is needed, for the reason you mentioned 
above.