netdev - RE: [PATCH v1 net] tipc: Fix use-after-free in tipc_conn

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Message-ID:
 <GV1P189MB1988EC63CDCBE8DFE53CFD61C640A@GV1P189MB1988.EURP189.PROD.OUTLOOK.COM>
Date: Wed, 2 Jul 2025 06:34:24 +0000
From: Tung Quang Nguyen <tung.quang.nguyen@....tech>
To: Kuniyuki Iwashima <kuniyu@...gle.com>, Jon Maloy <jmaloy@...hat.com>,
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
CC: Simon Horman <horms@...nel.org>, Ying Xue <ying.xue@...driver.com>,
	Kuniyuki Iwashima <kuni1840@...il.com>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "tipc-discussion@...ts.sourceforge.net"
	<tipc-discussion@...ts.sourceforge.net>,
	"syzbot+d333febcf8f4bc5f6110@...kaller.appspotmail.com"
	<syzbot+d333febcf8f4bc5f6110@...kaller.appspotmail.com>
Subject: RE: [PATCH v1 net] tipc: Fix use-after-free in tipc_conn_close().

>Subject: [PATCH v1 net] tipc: Fix use-after-free in tipc_conn_close().
>
>syzbot reported a null-ptr-deref in tipc_conn_close() during netns dismantle.
>[0]
>
>tipc_topsrv_stop() iterates tipc_net(net)->topsrv->conn_idr and calls
>tipc_conn_close() for each tipc_conn.
>
>The problem is that tipc_conn_close() is called after releasing the IDR lock.
>
>At the same time, there might be tipc_conn_recv_work() running and it could
>call tipc_conn_close() for the same tipc_conn and release its last ->kref.
>
>Once we release the IDR lock in tipc_topsrv_stop(), there is no guarantee that
>the tipc_conn is alive.
>
>Let's hold the ref before releasing the lock and put the ref after
>tipc_conn_close() in tipc_topsrv_stop().
>
>[0]:
>BUG: KASAN: use-after-free in tipc_conn_close+0x122/0x140
>net/tipc/topsrv.c:165 Read of size 8 at addr ffff888099305a08 by task
>kworker/u4:3/435
>
>CPU: 0 PID: 435 Comm: kworker/u4:3 Not tainted 4.19.204-syzkaller #0
>Hardware name: Google Google Compute Engine/Google Compute Engine,
>BIOS Google 01/01/2011
>Workqueue: netns cleanup_net
>Call Trace:
> __dump_stack lib/dump_stack.c:77 [inline]  dump_stack+0x1fc/0x2ef
>lib/dump_stack.c:118
> print_address_description.cold+0x54/0x219 mm/kasan/report.c:256
> kasan_report_error.cold+0x8a/0x1b9 mm/kasan/report.c:354  kasan_report
>mm/kasan/report.c:412 [inline]
> __asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433
> tipc_conn_close+0x122/0x140 net/tipc/topsrv.c:165  tipc_topsrv_stop
>net/tipc/topsrv.c:701 [inline]
> tipc_topsrv_exit_net+0x27b/0x5c0 net/tipc/topsrv.c:722
> ops_exit_list+0xa5/0x150 net/core/net_namespace.c:153
> cleanup_net+0x3b4/0x8b0 net/core/net_namespace.c:553
> process_one_work+0x864/0x1570 kernel/workqueue.c:2153
> worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
> kthread+0x33f/0x460 kernel/kthread.c:259
> ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
>
>Allocated by task 23:
> kmem_cache_alloc_trace+0x12f/0x380 mm/slab.c:3625  kmalloc
>include/linux/slab.h:515 [inline]  kzalloc include/linux/slab.h:709 [inline]
> tipc_conn_alloc+0x43/0x4f0 net/tipc/topsrv.c:192
> tipc_topsrv_accept+0x1b5/0x280 net/tipc/topsrv.c:470
> process_one_work+0x864/0x1570 kernel/workqueue.c:2153
> worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
> kthread+0x33f/0x460 kernel/kthread.c:259
> ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
>
>Freed by task 23:
> __cache_free mm/slab.c:3503 [inline]
> kfree+0xcc/0x210 mm/slab.c:3822
> tipc_conn_kref_release net/tipc/topsrv.c:150 [inline]  kref_put
>include/linux/kref.h:70 [inline]
> conn_put+0x2cd/0x3a0 net/tipc/topsrv.c:155
> process_one_work+0x864/0x1570 kernel/workqueue.c:2153
> worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
> kthread+0x33f/0x460 kernel/kthread.c:259
> ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
>
>The buggy address belongs to the object at ffff888099305a00  which belongs to
>the cache kmalloc-512 of size 512 The buggy address is located 8 bytes inside
>of  512-byte region [ffff888099305a00, ffff888099305c00) The buggy address
>belongs to the page:
>page:ffffea000264c140 count:1 mapcount:0 mapping:ffff88813bff0940
>index:0x0
>flags: 0xfff00000000100(slab)
>raw: 00fff00000000100 ffffea00028b6b88 ffffea0002cd2b08 ffff88813bff0940
>raw: 0000000000000000 ffff888099305000 0000000100000006
>0000000000000000 page dumped because: kasan: bad access detected
>
>Memory state around the buggy address:
> ffff888099305900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff888099305980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>ffff888099305a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                      ^
> ffff888099305a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff888099305b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>
>Fixes: c5fa7b3cf3cb ("tipc: introduce new TIPC server infrastructure")
>Reported-by: syzbot+d333febcf8f4bc5f6110@...kaller.appspotmail.com
>Closes: https://syzkaller.appspot.com/bug?extid=27169a847a70550d17be
>Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
>---
> net/tipc/topsrv.c | 2 ++
> 1 file changed, 2 insertions(+)
>
>diff --git a/net/tipc/topsrv.c b/net/tipc/topsrv.c index
>8ee0c07d00e9..ffe577bf6b51 100644
>--- a/net/tipc/topsrv.c
>+++ b/net/tipc/topsrv.c
>@@ -704,8 +704,10 @@ static void tipc_topsrv_stop(struct net *net)
> 	for (id = 0; srv->idr_in_use; id++) {
> 		con = idr_find(&srv->conn_idr, id);
> 		if (con) {
>+			conn_get(con);
> 			spin_unlock_bh(&srv->idr_lock);
> 			tipc_conn_close(con);
>+			conn_put(con);
> 			spin_lock_bh(&srv->idr_lock);
> 		}
> 	}
>--
>2.50.0.727.gbf7dc18ff4-goog
>
Reviewed-by: Tung Nguyen <tung.quang.nguyen@....tech>