AZL-92724

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

netfilter: x_tables: allocate hook ops while under mutex

arp/ip(6)tregistertable() add the table to the per-netns list via xtregistertable() before allocating the per-netns hook ops copy via kmemdup_array(). This leaves a window where the table is visible in the list with ops=NULL.

If the pernet exit happens runs concurrently the preexit callback finds the table via xtfindtable() and passes the NULL ops pointer to nfunregisternethooks(), causing a NULL dereference:

general protection fault in nfunregisternethooks+0xbc/0x150 RIP: nfunregisternethooks (net/netfilter/core.c:613) Call Trace: iptunregistertablepreexit iptablemanglenetpreexit opspreexitlist cleanupnet

Fix by moving the ops allocation into the xtables core so the table is never in the list without valid ops. Also ensure the table is no longer processing packets before its torn down on error unwind. nfregisternethooks might have published at least one hook; call synchronizercu() if there was an error.

audit log register message gets deferred until all operations have passed, this avoids need to emit another ureg message in case of error unwinding.

Based on earlier patch by Tristan Madani.