[PATCH net-next] net/netlink: fix NETLINK_LIST_MEMBERSHIPS length report

[PATCH net-next] net/netlink: fix NETLINK_LIST_MEMBERSHIPS length report

[Pedro Tammela]

The current code for the length calculation wrongly truncates the reported
length of the groups array, causing an under report of the subscribed
groups. To fix this, use 'BITS_TO_BYTES()' which rounds up the
division by 8.

Fixes: b42be38b2778 ("netlink: add API to retrieve all group memberships")
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
---
 net/netlink/af_netlink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index c87804112d0c..3a1e0fd5bf14 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1779,7 +1779,7 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname,
 				break;
 			}
 		}
-		if (put_user(ALIGN(nlk->ngroups / 8, sizeof(u32)), optlen))
+		if (put_user(ALIGN(BITS_TO_BYTES(nlk->ngroups), sizeof(u32)), optlen))
 			err = -EFAULT;
 		netlink_unlock_table();
 		return err;
-- 
2.39.2

Re: [PATCH net-next] net/netlink: fix NETLINK_LIST_MEMBERSHIPS length report

[Simon Horman]

On Mon, May 29, 2023 at 12:33:35PM -0300, Pedro Tammela wrote:
> The current code for the length calculation wrongly truncates the reported
> length of the groups array, causing an under report of the subscribed
> groups. To fix this, use 'BITS_TO_BYTES()' which rounds up the
> division by 8.
> 
> Fixes: b42be38b2778 ("netlink: add API to retrieve all group memberships")
> Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>

Reviewed-by: Simon Horman <simon.horman@corigine.com>

Re: [PATCH net-next] net/netlink: fix NETLINK_LIST_MEMBERSHIPS length report

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 29 May 2023 12:33:35 -0300 you wrote:
> The current code for the length calculation wrongly truncates the reported
> length of the groups array, causing an under report of the subscribed
> groups. To fix this, use 'BITS_TO_BYTES()' which rounds up the
> division by 8.
> 
> Fixes: b42be38b2778 ("netlink: add API to retrieve all group memberships")
> Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
> 
> [...]

Here is the summary with links:
  - [net-next] net/netlink: fix NETLINK_LIST_MEMBERSHIPS length report
    https://git.kernel.org/netdev/net/c/f4e4534850a9

You are awesome, thank you!
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