CVE-2022-49916

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

rose: Fix NULL pointer dereference in rose_send_frame()

The syzkaller reported an issue:

KASAN: null-ptr-deref in range [0x0000000000000380-0x0000000000000387] CPU: 0 PID: 4069 Comm: kworker/0:15 Not tainted 6.0.0-syzkaller-02734-g0326074ff465 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022 Workqueue: rcu_gp srcu_invoke_callbacks RIP: 0010:rose_send_frame+0x1dd/0x2f0 net/rose/rose_link.c:101 Call Trace: rose_transmit_clear_request+0x1d5/0x290 net/rose/rose_link.c:255 rose_rx_call_request+0x4c0/0x1bc0 net/rose/af_rose.c:1009 rose_loopback_timer+0x19e/0x590 net/rose/rose_loopback.c:111 call_timer_fn+0x1a0/0x6b0 kernel/time/timer.c:1474 expire_timers kernel/time/timer.c:1519 [inline] __run_timers.part.0+0x674/0xa80 kernel/time/timer.c:1790 __run_timers kernel/time/timer.c:1768 [inline] run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1803 __do_softirq+0x1d0/0x9c8 kernel/softirq.c:571 […]

It triggers NULL pointer dereference when neigh->dev->dev_addr is called in the rose_send_frame(). Its the first occurrence of the neigh is in rose_loopback_timer() as `rose_loopback_neigh, and the dev in rose_loopback_neigh is initialized sa nullptr.

It had been fixed by commit 3b3fd068c56e3fbea30090859216a368398e39bf (rose: Fix Null pointer dereference in rose_send_frame()) ever. But its introduced by commit 3c53cd65dece47dd1f9d3a809f32e59d1d87b2b8 (rose: check NULL rose_loopback_neigh->loopback) again.

We fix it by add NULL check in rose_transmit_clear_request(). When the dev in neigh is NULL, we dont reply the request and just clear it.

syzkaller dont provide repro, and I provide a syz repro like: r0 = syz_init_net_socket$bt_sco(0x1f, 0x5, 0x2) ioctl$sock_inet_SIOCSIFFLAGS(r0, 0x8914, &(0x7f0000000180)={rose0x00, 0x201}) r1 = syz_init_net_socket$rose(0xb, 0x5, 0x0) bind$rose(r1, &(0x7f00000000c0)=@full={0xb, @dev, @null, 0x0, [@null, @null, @netrom, @netrom, @default, @null]}, 0x40) connect$rose(r1, &(0x7f0000000240)=@short={0xb, @dev={0xbb, 0xbb, 0xbb, 0x1, 0x0}, @remote={0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0x1}, 0x1, @netrom={0xbb, 0xbb, 0xbb, 0xbb, 0xbb, 0x0, 0x0}}, 0x1c)

Weakness

The product dereferences a pointer that it expects to be valid but is NULL.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/01b9c68c121847d05a4ccef68244dadf82bfa331
• https://git.kernel.org/stable/c/3e2129c67daca21043a26575108f6286c85e71f6
• https://git.kernel.org/stable/c/5b46adfbee1e429f33b10a88d6c00fa88f3d6c77
• https://git.kernel.org/stable/c/a601e5eded33bb88b8a42743db8fef3ad41dd97e
• https://git.kernel.org/stable/c/b13be5e852b03f376058027e462fad4230240891
• https://git.kernel.org/stable/c/bbc03d74e641e824754443b908454ca9e203773e
• https://git.kernel.org/stable/c/e97c089d7a49f67027395ddf70bf327eeac2611e
• https://git.kernel.org/stable/c/f06186e5271b980bac03f5c97276ed0146ddc9b0