Date: Sat, 2 Apr 2022 16:14:37 +0800 (GMT+08:00) From: 周多明 <duoming@....edu.cn> To: oss-security@...ts.openwall.com Subject: CVE-2022-1205 kernel: Null pointer dereference and use-after-free in net/ax25/ax25_timer.c Hello there, There are NPD and use-after-free vulnerabilities in net/ax25/ax25_timer.c of linux that allow attacker to crash linux kernel by simulating ax25 device from user space. =*=*=*=*=*=*=*=*= Bug Details =*=*=*=*=*=*=*=*= There are race conditions that may lead to null pointer dereferences in ax25_heartbeat_expiry(), ax25_t1timer_expiry(), ax25_t2timer_expiry(), ax25_t3timer_expiry() and ax25_idletimer_expiry(), when we use ax25_kill_by_device() to detach the ax25 device. One of the race conditions that cause null pointer dereferences can be shown as below: (Thread 1) | (Thread 2) ax25_connect() | ax25_std_establish_data_link() | ax25_start_t1timer() | mod_timer(&ax25->t1timer,..) | | ax25_kill_by_device() (wait a time) | ... | s->ax25_dev = NULL; //(1) ax25_t1timer_expiry() | ax25->ax25_dev->values[..] //(2)| ... ... | We set null to ax25_cb->ax25_dev in position (1) and dereference the null pointer in position (2). There are also race conditions that may lead to UAF bugs in ax25_heartbeat_expiry(), ax25_t1timer_expiry(), ax25_t2timer_expiry(), ax25_t3timer_expiry() and ax25_idletimer_expiry(), when we call ax25_release() to deallocate ax25_dev. (Thread 1) | (Thread 2) ax25_dev_device_up() //(1) | ... | ax25_kill_by_device() ax25_bind() //(2) | ax25_connect() | ... ax25_std_establish_data_link() | ax25_start_t1timer() | ax25_dev_device_down() //(3) mod_timer(&ax25->t1timer,..) | | ax25_release() (wait a time) | ... | ax25_dev_put(ax25_dev) //(4)FREE ax25_t1timer_expiry() | ax25->ax25_dev->values[..] //USE| ... ... | We increase the refcount of ax25_dev in position (1) and (2), and decrease the refcount of ax25_dev in position (3) and (4). The ax25_dev will be freed in position (4) and be used in ax25_t1timer_expiry(). =*=*=*=*=*=*=*=*= Bug Effects =*=*=*=*=*=*=*=*= We can successfully trigger the NPD and UAF vulnerabilities to crash the linux kernel. BUG: kernel NULL pointer dereference, address: 0000000000000050 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.17.0-rc6-00794-g45690b7d0 RIP: 0010:ax25_t1timer_expiry+0x12/0x40 ... Call Trace: call_timer_fn+0x21/0x120 __run_timers.part.0+0x1ca/0x250 run_timer_softirq+0x2c/0x60 __do_softirq+0xef/0x2f3 irq_exit_rcu+0xb6/0x100 sysvec_apic_timer_interrupt+0xa2/0xd0 ... ============================================================== [ 106.116942] BUG: KASAN: use-after-free in ax25_t1timer_expiry+0x1c/0x60 [ 106.116942] Read of size 8 at addr ffff88800bda9028 by task swapper/0/0 [ 106.116942] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.17.0-06123-g0905eec574 [ 106.116942] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-14 [ 106.116942] Call Trace: ... [ 106.116942] ax25_t1timer_expiry+0x1c/0x60 [ 106.116942] call_timer_fn+0x122/0x3d0 [ 106.116942] __run_timers.part.0+0x3f6/0x520 [ 106.116942] run_timer_softirq+0x4f/0xb0 [ 106.116942] __do_softirq+0x1c2/0x651 ... =*=*=*=*=*=*=*=*= Bug Fix =*=*=*=*=*=*=*=*= The patch that have been applied to mainline Linux kernel is shown below. https://github.com/torvalds/linux/commit/fc6d01ff9ef03b66d4a3a23b46fc3c3d8cf92009 https://github.com/torvalds/linux/commit/82e31755e55fbcea6a9dfaae5fe4860ade17cbc0 =*=*=*=*=*=*=*=*= Timeline =*=*=*=*=*=*=*=*= 2022-03-21: commit fc6d01ff9ef0 accepted to mainline kernel 2022-03-29: commit 82e31755e55f accepted to mainline kernel 2022-04-01: CVE-2022-1205 is assigned =*=*=*=*=*=*=*=*= Credit =*=*=*=*=*=*=*=*= Duoming Zhou <duoming@....edu.cn> Best Regards, Duoming Zhou
Powered by blists - more mailing lists
Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.