[PATCH 3.16 305/366] netlink: Don't shift with UB on nlk->ngroups

Ben Hutchings
2018-11-12T05:48:25Z

From: Dmitry Safonov <dima@arista.com>

commit 61f4b23769f0cc72ae62c9a81cf08f0397d40da8 upstream.

On i386 nlk->ngroups might be 32 or 0. Which leads to UB, resulting in
hang during boot.
Check for 0 ngroups and use (unsigned long long) as a type to shift.

Fixes: 7acf9d4237c4 ("netlink: Do not subscribe to non-existent groups").
Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/netlink/af_netlink.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -927,7 +927,11 @@ static int netlink_bind(struct socket *s
if (err)
return err;
}
- groups &= (1UL << nlk->ngroups) - 1;
+
+ if (nlk->ngroups == 0)
+ groups = 0;
+ else
+ groups &= (1ULL << nlk->ngroups) - 1;

if (nlk->portid)
if (nladdr->nl_pid != nlk->portid)