CVE-2022-49904

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

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

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:_neighifdown.isra.0+0x24b/0x370 RSP: 0018:ffff888012677908 EFLAGS: 00000202 ... Call Trace: <TASK> neightableclear+0x94/0x2d0 ndisccleanup+0x27/0x40 [ipv6] inet6init+0x21c/0x2cb [ipv6] dooneinitcall+0xd3/0x4d0 doinitmodule+0x1ae/0x670 ... Kernel panic - not syncing: Fatal exception

When ipv6 initialization fails, it will try to cleanup and calls:

neightableclear() neighifdown(tbl, NULL) pneighqueuepurge(&tbl->proxyqueue, devnet(dev == NULL)) # devnet(NULL) triggers null-ptr-deref.

Fix it by passing NULL to pneighqueuepurge() in neigh_ifdown() if dev is NULL, to make kernel not panic immediately.