path: root/net/sctp/input.c
diff options
authorXin Long <lucien.xin@gmail.com>2019-10-08 19:09:23 +0800
committerJakub Kicinski <jakub.kicinski@netronome.com>2019-10-09 16:27:04 -0700
commit819be8108fded0b9e710bbbf81193e52f7bab2f7 (patch)
tree435781d818895e15928e95b7005eede3ded2e1d0 /net/sctp/input.c
parentbonding: fix potential NULL deref in bond_update_slave_arr (diff)
sctp: add chunks to sk_backlog when the newsk sk_socket is not set
This patch is to fix a NULL-ptr deref in selinux_socket_connect_helper: [...] kasan: GPF could be caused by NULL-ptr deref or user memory access [...] RIP: 0010:selinux_socket_connect_helper+0x94/0x460 [...] Call Trace: [...] selinux_sctp_bind_connect+0x16a/0x1d0 [...] security_sctp_bind_connect+0x58/0x90 [...] sctp_process_asconf+0xa52/0xfd0 [sctp] [...] sctp_sf_do_asconf+0x785/0x980 [sctp] [...] sctp_do_sm+0x175/0x5a0 [sctp] [...] sctp_assoc_bh_rcv+0x285/0x5b0 [sctp] [...] sctp_backlog_rcv+0x482/0x910 [sctp] [...] __release_sock+0x11e/0x310 [...] release_sock+0x4f/0x180 [...] sctp_accept+0x3f9/0x5a0 [sctp] [...] inet_accept+0xe7/0x720 It was caused by that the 'newsk' sk_socket was not set before going to security sctp hook when processing asconf chunk with SCTP_PARAM_ADD_IP or SCTP_PARAM_SET_PRIMARY: inet_accept()-> sctp_accept(): lock_sock(): lock listening 'sk' do_softirq(): sctp_rcv(): <-- [1] asconf chunk arrives and enqueued in 'sk' backlog sctp_sock_migrate(): set asoc's sk to 'newsk' release_sock(): sctp_backlog_rcv(): lock 'newsk' sctp_process_asconf() <-- [2] unlock 'newsk' sock_graft(): set sk_socket <-- [3] As it shows, at [1] the asconf chunk would be put into the listening 'sk' backlog, as accept() was holding its sock lock. Then at [2] asconf would get processed with 'newsk' as asoc's sk had been set to 'newsk'. However, 'newsk' sk_socket is not set until [3], while selinux_sctp_bind_connect() would deref it, then kernel crashed. Here to fix it by adding the chunk to sk_backlog until newsk sk_socket is set when .accept() is done. Note that sk->sk_socket can be NULL when the sock is closed, so SOCK_DEAD flag is also needed to check in sctp_newsk_ready(). Thanks to Ondrej for reviewing the code. Fixes: d452930fd3b9 ("selinux: Add SCTP support") Reported-by: Ying Xu <yinxu@redhat.com> Suggested-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Signed-off-by: Xin Long <lucien.xin@gmail.com> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Acked-by: Neil Horman <nhorman@tuxdriver.com> Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Diffstat (limited to '')
1 files changed, 9 insertions, 3 deletions
diff --git a/net/sctp/input.c b/net/sctp/input.c
index 5a070fb5b278..f2771375bfc0 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -243,7 +243,7 @@ int sctp_rcv(struct sk_buff *skb)
- if (sock_owned_by_user(sk)) {
+ if (sock_owned_by_user(sk) || !sctp_newsk_ready(sk)) {
if (sctp_add_backlog(sk, skb)) {
@@ -321,7 +321,7 @@ int sctp_backlog_rcv(struct sock *sk, struct sk_buff *skb)
- if (sock_owned_by_user(sk)) {
+ if (sock_owned_by_user(sk) || !sctp_newsk_ready(sk)) {
if (sk_add_backlog(sk, skb, sk->sk_rcvbuf))
@@ -336,7 +336,13 @@ int sctp_backlog_rcv(struct sock *sk, struct sk_buff *skb)
if (backloged)
return 0;
} else {
- sctp_inq_push(inqueue, chunk);
+ if (!sctp_newsk_ready(sk)) {
+ if (!sk_add_backlog(sk, skb, sk->sk_rcvbuf))
+ return 0;
+ sctp_chunk_free(chunk);
+ } else {
+ sctp_inq_push(inqueue, chunk);
+ }