netlink: Don't shift on 64 for ngroups

It's legal to have 64 groups for netlink_sock. As user-supplied nladdr->nl_groups is __u32, it's possible to subscribe only to first 32 groups. The check for correctness of .bind() userspace supplied parameter is done by applying mask made from ngroups shift. Which broke Android as they have 64 groups and the shift for mask resulted in an overflow. Fixes: 61f4b23 ("netlink: Don't shift with UB on nlk->ngroups") Cc: "David S. Miller" <[email protected]> Cc: Herbert Xu <[email protected]> Cc: Steffen Klassert <[email protected]> Cc: [email protected] Cc: [email protected] Reported-and-Tested-by: Nathan Chancellor <[email protected]> Signed-off-by: Dmitry Safonov <[email protected]> Signed-off-by: David S. Miller <[email protected]>
tadfisher · Aug 5, 2018 · 91874ec · 91874ec
1 parent 5dbfb6e
commit 91874ec
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
@@ -1013,8 +1013,8 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr,
 
 	if (nlk->ngroups == 0)
 		groups = 0;
-	else
-		groups &= (1ULL << nlk->ngroups) - 1;
+	else if (nlk->ngroups < 8*sizeof(groups))
+		groups &= (1UL << nlk->ngroups) - 1;
 
 	bound = nlk->bound;
 	if (bound) {