[PATCH 4.19 024/105] tipc: add an extra conn_get in tipc_conn_alloc

Greg Kroah-Hartman
2022-12-05T19:18:47Z

From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit a7b42969d63f47320853a802efd879fbdc4e010e ]

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: c5fa7b3cf3cb ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/tipc/topsrv.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/tipc/topsrv.c b/net/tipc/topsrv.c
index 8ac27bd786f3..d3bb19cd0ec0 100644
--- a/net/tipc/topsrv.c
+++ b/net/tipc/topsrv.c
@@ -214,6 +214,7 @@ static struct tipc_conn *tipc_conn_alloc(struct tipc_topsrv *s, struct socket *s
set_bit(CF_CONNECTED, &con->flags);
con->server = s;
con->sock = sock;
+ conn_get(con);
spin_unlock_bh(&s->idr_lock);

return con;
@@ -491,6 +492,7 @@ static void tipc_topsrv_accept(struct work_struct *work)

/* Wake up receive process in case of 'SYN+' message */
newsk->sk_data_ready(newsk);
+ conn_put(con);
}
}

@@ -590,10 +592,11 @@ bool tipc_topsrv_kern_subscr(struct net *net, u32 port, u32 type, u32 lower,

*conid = con->conid;
rc = tipc_conn_rcv_sub(tipc_topsrv(net), con, &sub);
- if (rc >= 0)
- return true;
+ if (rc)
+ conn_put(con);
+
conn_put(con);
- return false;
+ return !rc;
}

void tipc_topsrv_kern_unsubscr(struct net *net, int conid)
--
2.35.1