CVE-2025-38464
Publication date:
25/07/2025
In the Linux kernel, the following vulnerability has been resolved:<br />
<br />
tipc: Fix use-after-free in tipc_conn_close().<br />
<br />
syzbot reported a null-ptr-deref in tipc_conn_close() during netns<br />
dismantle. [0]<br />
<br />
tipc_topsrv_stop() iterates tipc_net(net)->topsrv->conn_idr and calls<br />
tipc_conn_close() for each tipc_conn.<br />
<br />
The problem is that tipc_conn_close() is called after releasing the<br />
IDR lock.<br />
<br />
At the same time, there might be tipc_conn_recv_work() running and it<br />
could call tipc_conn_close() for the same tipc_conn and release its<br />
last ->kref.<br />
<br />
Once we release the IDR lock in tipc_topsrv_stop(), there is no<br />
guarantee that the tipc_conn is alive.<br />
<br />
Let&#39;s hold the ref before releasing the lock and put the ref after<br />
tipc_conn_close() in tipc_topsrv_stop().<br />
<br />
[0]:<br />
BUG: KASAN: use-after-free in tipc_conn_close+0x122/0x140 net/tipc/topsrv.c:165<br />
Read of size 8 at addr ffff888099305a08 by task kworker/u4:3/435<br />
<br />
CPU: 0 PID: 435 Comm: kworker/u4:3 Not tainted 4.19.204-syzkaller #0<br />
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011<br />
Workqueue: netns cleanup_net<br />
Call Trace:<br />
__dump_stack lib/dump_stack.c:77 [inline]<br />
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118<br />
print_address_description.cold+0x54/0x219 mm/kasan/report.c:256<br />
kasan_report_error.cold+0x8a/0x1b9 mm/kasan/report.c:354<br />
kasan_report mm/kasan/report.c:412 [inline]<br />
__asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433<br />
tipc_conn_close+0x122/0x140 net/tipc/topsrv.c:165<br />
tipc_topsrv_stop net/tipc/topsrv.c:701 [inline]<br />
tipc_topsrv_exit_net+0x27b/0x5c0 net/tipc/topsrv.c:722<br />
ops_exit_list+0xa5/0x150 net/core/net_namespace.c:153<br />
cleanup_net+0x3b4/0x8b0 net/core/net_namespace.c:553<br />
process_one_work+0x864/0x1570 kernel/workqueue.c:2153<br />
worker_thread+0x64c/0x1130 kernel/workqueue.c:2296<br />
kthread+0x33f/0x460 kernel/kthread.c:259<br />
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415<br />
<br />
Allocated by task 23:<br />
kmem_cache_alloc_trace+0x12f/0x380 mm/slab.c:3625<br />
kmalloc include/linux/slab.h:515 [inline]<br />
kzalloc include/linux/slab.h:709 [inline]<br />
tipc_conn_alloc+0x43/0x4f0 net/tipc/topsrv.c:192<br />
tipc_topsrv_accept+0x1b5/0x280 net/tipc/topsrv.c:470<br />
process_one_work+0x864/0x1570 kernel/workqueue.c:2153<br />
worker_thread+0x64c/0x1130 kernel/workqueue.c:2296<br />
kthread+0x33f/0x460 kernel/kthread.c:259<br />
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415<br />
<br />
Freed by task 23:<br />
__cache_free mm/slab.c:3503 [inline]<br />
kfree+0xcc/0x210 mm/slab.c:3822<br />
tipc_conn_kref_release net/tipc/topsrv.c:150 [inline]<br />
kref_put include/linux/kref.h:70 [inline]<br />
conn_put+0x2cd/0x3a0 net/tipc/topsrv.c:155<br />
process_one_work+0x864/0x1570 kernel/workqueue.c:2153<br />
worker_thread+0x64c/0x1130 kernel/workqueue.c:2296<br />
kthread+0x33f/0x460 kernel/kthread.c:259<br />
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415<br />
<br />
The buggy address belongs to the object at ffff888099305a00<br />
which belongs to the cache kmalloc-512 of size 512<br />
The buggy address is located 8 bytes inside of<br />
512-byte region [ffff888099305a00, ffff888099305c00)<br />
The buggy address belongs to the page:<br />
page:ffffea000264c140 count:1 mapcount:0 mapping:ffff88813bff0940 index:0x0<br />
flags: 0xfff00000000100(slab)<br />
raw: 00fff00000000100 ffffea00028b6b88 ffffea0002cd2b08 ffff88813bff0940<br />
raw: 0000000000000000 ffff888099305000 0000000100000006 0000000000000000<br />
page dumped because: kasan: bad access detected<br />
<br />
Memory state around the buggy address:<br />
ffff888099305900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb<br />
ffff888099305980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc<br />
>ffff888099305a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb<br />
^<br />
ffff888099305a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb<br />
ffff888099305b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
Severity CVSS v4.0: Pending analysis
Last modification:
22/12/2025