ChunYu found a netlink use-after-free issue by syzkaller:
[28448.842981] BUG: KASAN: use-after-free in __nla_put+0x37/0x40 at addr
ffff8807185e2378
[28448.969918] Call Trace:
[...]
[28449.117207] __nla_put+0x37/0x40
[28449.132027] nla_put+0xf5/0x130
[28449.146261] sk_diag_fill.isra.4.constprop.5+0x5a0/0x750 [netlink_diag]
[28449.176608] __netlink_diag_dump+0x25a/0x700 [netlink_diag]
[28449.202215] netlink_diag_dump+0x176/0x240 [netlink_diag]
[28449.226834] netlink_dump+0x488/0xbb0
[28449.298014] __netlink_dump_start+0x4e8/0x760
[28449.317924] netlink_diag_handler_dump+0x261/0x340 [netlink_diag]
[28449.413414] sock_diag_rcv_msg+0x207/0x390
[28449.432409] netlink_rcv_skb+0x149/0x380
[28449.467647] sock_diag_rcv+0x2d/0x40
[28449.484362] netlink_unicast+0x562/0x7b0
[28449.564790] netlink_sendmsg+0xaa8/0xe60
[28449.661510] sock_sendmsg+0xcf/0x110
[28449.865631] __sys_sendmsg+0xf3/0x240
[28450.000964] SyS_sendmsg+0x32/0x50
[28450.016969] do_syscall_64+0x25c/0x6c0
[28450.154439] entry_SYSCALL64_slow_path+0x25/0x25
It was caused by no protection between nlk groups' free in netlink_release
and nlk groups' accessing in sk_diag_dump_groups. The similar issue also
exists in netlink_seq_show().
This patch is to defer nlk groups' free in deferred_put_nlk_sk.
Reported-by: ChunYu Wang <chunw...@redhat.com>
Acked-by: Florian Westphal <f...@strlen.de>
Signed-off-by: Xin Long <lucien....@gmail.com>
---
net/netlink/af_netlink.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 5acee49..94a61e6 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -691,6 +691,9 @@ static void deferred_put_nlk_sk(struct rcu_head *head)
struct netlink_sock *nlk = container_of(head, struct netlink_sock, rcu);
struct sock *sk = &nlk->sk;
+ kfree(nlk->groups);
+ nlk->groups = NULL;
+
if (!refcount_dec_and_test(&sk->sk_refcnt))
return;
@@ -769,9 +772,6 @@ static int netlink_release(struct socket *sock)
netlink_table_ungrab();
}
- kfree(nlk->groups);
- nlk->groups = NULL;
-
local_bh_disable();
sock_prot_inuse_add(sock_net(sk), &netlink_proto, -1);
local_bh_enable();
--
2.1.0
