4.9-stable review patch. If anyone has any objections, please let me know.
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From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit f7e43672683b097bb074a8fe7af9bc600a23f231 ]
syzbot reported we still access llc->sap in llc_backlog_rcv() after it is freed in llc_sap_remove_socket():
Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1b9/0x294 lib/dump_stack.c:113 print_address_description+0x6c/0x20b mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430 llc_conn_ac_send_sabme_cmd_p_set_x+0x3a8/0x460 net/llc/llc_c_ac.c:785 llc_exec_conn_trans_actions net/llc/llc_conn.c:475 [inline] llc_conn_service net/llc/llc_conn.c:400 [inline] llc_conn_state_process+0x4e1/0x13a0 net/llc/llc_conn.c:75 llc_backlog_rcv+0x195/0x1e0 net/llc/llc_conn.c:891 sk_backlog_rcv include/net/sock.h:909 [inline] __release_sock+0x12f/0x3a0 net/core/sock.c:2335 release_sock+0xa4/0x2b0 net/core/sock.c:2850 llc_ui_release+0xc8/0x220 net/llc/af_llc.c:204
llc->sap is refcount'ed and llc_sap_remove_socket() is paired with llc_sap_add_socket(). This can be amended by holding its refcount before llc_sap_remove_socket() and releasing it after release_sock().
Reported-by: syzbot+6e181fc95081c2cf9051@syzkaller.appspotmail.com Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/llc/af_llc.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/net/llc/af_llc.c +++ b/net/llc/af_llc.c @@ -187,6 +187,7 @@ static int llc_ui_release(struct socket { struct sock *sk = sock->sk; struct llc_sock *llc; + struct llc_sap *sap;
if (unlikely(sk == NULL)) goto out; @@ -197,9 +198,15 @@ static int llc_ui_release(struct socket llc->laddr.lsap, llc->daddr.lsap); if (!llc_send_disc(sk)) llc_ui_wait_for_disc(sk, sk->sk_rcvtimeo); + sap = llc->sap; + /* Hold this for release_sock(), so that llc_backlog_rcv() could still + * use it. + */ + llc_sap_hold(sap); if (!sock_flag(sk, SOCK_ZAPPED)) llc_sap_remove_socket(llc->sap, sk); release_sock(sk); + llc_sap_put(sap); if (llc->dev) dev_put(llc->dev); sock_put(sk);