On Thu, Oct 17, 2013 at 02:24:33PM +0100, Will Deacon wrote: > During kernel stability testing on an SMP ARMv7 system, Yalin Wang > reported the following panic from the netfilter code: > > 1fe0: 0000001c 5e2d3b10 4007e779 4009e110 60000010 00000032 ff565656 ff545454 > [<c06c48dc>] (ipt_do_table+0x448/0x584) from [<c0655ef0>] (nf_iterate+0x48/0x7c) > [<c0655ef0>] (nf_iterate+0x48/0x7c) from [<c0655f7c>] (nf_hook_slow+0x58/0x104) > [<c0655f7c>] (nf_hook_slow+0x58/0x104) from [<c0683bbc>] (ip_local_deliver+0x88/0xa8) > [<c0683bbc>] (ip_local_deliver+0x88/0xa8) from [<c0683718>] (ip_rcv_finish+0x418/0x43c) > [<c0683718>] (ip_rcv_finish+0x418/0x43c) from [<c062b1c4>] (__netif_receive_skb+0x4cc/0x598) > [<c062b1c4>] (__netif_receive_skb+0x4cc/0x598) from [<c062b314>] (process_backlog+0x84/0x158) > [<c062b314>] (process_backlog+0x84/0x158) from [<c062de84>] (net_rx_action+0x70/0x1dc) > [<c062de84>] (net_rx_action+0x70/0x1dc) from [<c0088230>] (__do_softirq+0x11c/0x27c) > [<c0088230>] (__do_softirq+0x11c/0x27c) from [<c008857c>] (do_softirq+0x44/0x50) > [<c008857c>] (do_softirq+0x44/0x50) from [<c0088614>] (local_bh_enable_ip+0x8c/0xd0) > [<c0088614>] (local_bh_enable_ip+0x8c/0xd0) from [<c06b0330>] (inet_stream_connect+0x164/0x298) > [<c06b0330>] (inet_stream_connect+0x164/0x298) from [<c061d68c>] (sys_connect+0x88/0xc8) > [<c061d68c>] (sys_connect+0x88/0xc8) from [<c000e340>] (ret_fast_syscall+0x0/0x30) > Code: 2a000021 e59d2028 e59de01c e59f011c (e7824103) > ---[ end trace da227214a82491bd ]--- > Kernel panic - not syncing: Fatal exception in interrupt > > This comes about because CPU1 is executing xt_replace_table in response > to a setsockopt syscall, resulting in: > > ret = xt_jumpstack_alloc(newinfo); > --> newinfo->jumpstack = kzalloc(size, GFP_KERNEL); > > [...] > > table->private = newinfo; > newinfo->initial_entries = private->initial_entries; > > Meanwhile, CPU0 is handling the network receive path and ends up in > ipt_do_table, resulting in: > > private = table->private; > > [...] > > jumpstack = (struct ipt_entry **)private->jumpstack[cpu]; > > On weakly ordered memory architectures, the writes to table->private > and newinfo->jumpstack from CPU1 can be observed out of order by CPU0. > Furthermore, on architectures which don't respect ordering of address > dependencies (i.e. Alpha), the reads from CPU0 can also be re-ordered. > > This patch adds an smp_wmb() before the assignment to table->private > (which is essentially publishing newinfo) to ensure that all writes to > newinfo will be observed before plugging it into the table structure. > A dependent-read barrier is also added on the consumer side, to ensure > the same ordering requirement are also respected there. We also need fixes for net/ipv6/netfilter/ip6_tables.c and net/ipv4/netfilter/arp_tables.c as well. Could you extend this patch and resend? Thanks! -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
