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authorXin Long <lucien.xin@gmail.com>2017-09-06 05:47:12 +0200
committerDavid S. Miller <davem@davemloft.net>2017-09-07 06:22:53 +0200
commitbe82485fbcbb1cf11b13e7356231c72fdf21241c (patch)
treececff3d0ec55ca784f503188ab4b4d4fbef37466
parentsched: Use __qdisc_drop instead of kfree_skb in sch_prio and sch_qfq (diff)
downloadlinux-be82485fbcbb1cf11b13e7356231c72fdf21241c.tar.xz
linux-be82485fbcbb1cf11b13e7356231c72fdf21241c.zip
netlink: fix an use-after-free issue for nlk groups
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 <chunwang@redhat.com> Acked-by: Florian Westphal <fw@strlen.de> Signed-off-by: Xin Long <lucien.xin@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/netlink/af_netlink.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 5acee49db90b..94a61e602ee7 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();