One extra conn_get() is needed in tipc_conn_alloc(), as after
tipc_conn_alloc() is called, tipc_conn_close() may free this
con before deferencing it in tipc_topsrv_accept():
tipc_conn_alloc();
newsk = newsock->sk;
<---- tipc_conn_close();
write_lock_bh(&sk->sk_callback_lock);
newsk->sk_data_ready = tipc_conn_data_ready;
Then an uaf issue can be triggered:
BUG: KASAN: use-after-free in tipc_topsrv_accept+0x1e7/0x370 [tipc]
Call Trace:
<TASK>
dump_stack_lvl+0x33/0x46
print_report+0x178/0x4b0
kasan_report+0x8c/0x100
kasan_check_range+0x179/0x1e0
tipc_topsrv_accept+0x1e7/0x370 [tipc]
process_one_work+0x6a3/0x1030
worker_thread+0x8a/0xdf0
This patch fixes it by holding it in tipc_conn_alloc(), then after
all accessing in tipc_topsrv_accept() releasing it. Note when does
this in tipc_topsrv_kern_subscr(), as tipc_conn_rcv_sub() returns
0 or -1 only, we don't need to check for "> 0".
Fixes: c5fa7b3cf3 ("tipc: introduce new TIPC server infrastructure")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
a7b42969d6