net, neigh: Fix null-ptr-deref in neigh_table_clear()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: net, neigh: Fix null-ptr-deref in neigh_table_clear() When IPv6 module gets initialized but hits an error in the middle, kenel panic with: KASAN: null-ptr-deref in range [0x0000000000000598-0x000000000000059f] CPU: 1 PID: 361 Comm: insmod Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) RIP: 0010:__neigh_ifdown.isra.0+0x24b/0x370 RSP: 0018:ffff888012677908 EFLAGS: 00000202 ... Call Trace: <TASK> neigh_table_clear+0x94/0x2d0 ndisc_cleanup+0x27/0x40 [ipv6] inet6_init+0x21c/0x2cb [ipv6] do_one_initcall+0xd3/0x4d0 do_init_module+0x1ae/0x670 ... Kernel panic - not syncing: Fatal exception When ipv6 initialization fails, it will try to cleanup and calls: neigh_table_clear() neigh_ifdown(tbl, NULL) pneigh_queue_purge(&tbl->proxy_queue, dev_net(dev == NULL)) # dev_net(NULL) triggers null-ptr-deref. Fix it by passing NULL to pneigh_queue_purge() in neigh_ifdown() if dev is NULL, to make kernel not panic immediately.

References

• https://git.kernel.org/stable/c/0d38b4ca6679e72860ff8730e79bb99d0e9fa3b0
• https://git.kernel.org/stable/c/b736592de2aa53aee2d48d6b129bc0c892007bbe
• https://git.kernel.org/stable/c/b49f6b2f21f543d4dc88fb7b1ec2adccb822f27c
• https://git.kernel.org/stable/c/1c89642e7f2b7ecc9635610653f5c2f0276c0051
• https://git.kernel.org/stable/c/2b45d6d0c41cb9593868e476681efb1aae5078a1
• https://git.kernel.org/stable/c/a99a8ec4c62180c889482a2ff6465033e0743458
• https://git.kernel.org/stable/c/f8017317cb0b279b8ab98b0f3901a2e0ac880dad