CVE-2024-44934 net: bridge: mcast: wait for previous gc cycles when removing port
A use-after-free in the Linux kernel bridge multicast code allows attackers to cause denial of service or potentially execute code.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-44934?
CVE-2024-44934 is a high-severity use after free vulnerability in Linux kernel, published on 26 Aug 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net: bridge: mcast: wait for previous gc cycles when removing port
syzbot hit a use-after-free[1] which is caused because the bridge doesn't make sure that all previous garbage has been collected when removing a port. What happens is: CPU 1 CPU 2 start gc cycle remove port acquire gc lock first wait for lock call br_multicasg_gc() directly acquire lock now but free port the port can be freed while grp timers still running
Make sure all previous gc cycles have finished by using flush_work before freeing the port.
[1] BUG: KASAN: slab-use-after-free in br_multicast_port_group_expired+0x4c0/0x550 net/bridge/br_multicast.c:861 Read of size 8 at addr ffff888071d6d000 by task syz.5.1232/9699
CPU: 1 PID: 9699 Comm: syz.5.1232 Not tainted 6.10.0-rc5-syzkaller-00021-g24ca36a562d6 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024 Call Trace: <IRQ> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114 print_address_description mm/kasan/report.c:377 [inline] print_report+0xc3/0x620 mm/kasan/report.c:488 kasan_report+0xd9/0x110 mm/kasan/report.c:601 br_multicast_port_group_expired+0x4c0/0x550 net/bridge/br_multicast.c:861 call_timer_fn+0x1a3/0x610 kernel/time/timer.c:1792 expire_timers kernel/time/timer.c:1843 [inline] __run_timers+0x74b/0xaf0 kernel/time/timer.c:2417 __run_timer_base kernel/time/timer.c:2428 [inline] __run_timer_base kernel/time/timer.c:2421 [inline] run_timer_base+0x111/0x190 kernel/time/timer.c:2437
Weakness: CWE-416
Which versions are affected by CVE-2024-44934?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-44934?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2024-44934 being exploited?
There is no known exploitation of CVE-2024-44934 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-48288, BELL-CVE-2024-44934, DEBIAN-CVE-2024-44934, GHSA-3pph-x43c-2v7f, ROOT-OS-DEBIAN-11-CVE-2024-44934, UBUNTU-CVE-2024-44934.