CVE-2025-38666

In the Linux kernel, the following vulnerability has been resolved:

net: appletalk: Fix use-after-free in AARP proxy probe

The AARP proxy‐probe routine (aarp_proxy_probe_network) sends a probe, releases the aarp_lock, sleeps, then re-acquires the lock. During that window an expire timer thread (__aarp_expire_timer) can remove and kfree() the same entry, leading to a use-after-free.

race condition:

     cpu 0                          |            cpu 1
atalk_sendmsg()                     |   atif_proxy_probe_device()
aarp_send_ddp()                     |   aarp_proxy_probe_network()
mod_timer()                         |   lock(aarp_lock) // LOCK!!
timeout around 200ms                |   alloc(aarp_entry)
and then call                       |   proxies[hash] = aarp_entry
aarp_expire_timeout()               |   aarp_send_probe()
                                    |   unlock(aarp_lock) // UNLOCK!!
lock(aarp_lock) // LOCK!!           |   msleep(100);
__aarp_expire_timer(&proxies[ct])   |
free(aarp_entry)                    |
unlock(aarp_lock) // UNLOCK!!       |
                                    |   lock(aarp_lock) // LOCK!!
                                    |   UAF aarp_entry !!

================================================================== BUG: KASAN: slab-use-after-free in aarp_proxy_probe_network+0x560/0x630 net/appletalk/aarp.c:493 Read of size 4 at addr ffff8880123aa360 by task repro/13278

CPU: 3 UID: 0 PID: 13278 Comm: repro Not tainted 6.15.2 #3 PREEMPT(full) Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:408 [inline] print_report+0xc1/0x630 mm/kasan/report.c:521 kasan_report+0xca/0x100 mm/kasan/report.c:634 aarp_proxy_probe_network+0x560/0x630 net/appletalk/aarp.c:493 atif_proxy_probe_device net/appletalk/ddp.c:332 [inline] atif_ioctl+0xb58/0x16c0 net/appletalk/ddp.c:857...