netfilter: use get_random_u32 instead of prandom

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: use get_random_u32 instead of prandom bh might occur while updating per-cpu rnd_state from user context, ie. local_out path. BUG: using smp_processor_id() in preemptible [00000000] code: nginx/2725 caller is nft_ng_random_eval+0x24/0x54 [nft_numgen] Call Trace: check_preemption_disabled+0xde/0xe0 nft_ng_random_eval+0x24/0x54 [nft_numgen] Use the random driver instead, this also avoids need for local prandom state. Moreover, prandom now uses the random driver since d4150779e60f ("random32: use real rng for non-deterministic randomness"). Based on earlier patch from Pablo Neira.

References

• https://git.kernel.org/stable/c/15cc30ac2a8d7185f8ebf97dd1ddd90a7c79783b
• https://git.kernel.org/stable/c/d0906b0fffc9f19bc42708ca3e84e2089088386c
• https://git.kernel.org/stable/c/6ce71f83f798be7e1ca68707fec449fbecb38852
• https://git.kernel.org/stable/c/b1fd94e704571f98b21027340eecf821b2bdffba