On Thu, Mar 22, 2018 at 11:08:50AM +0100, Paolo Abeni wrote: > The ipv4 nf_ct code currently skips the nf_conntrak_in() call > for fragmented packets. As a results later matches/target can end > up manipulating template ct entry instead of 'real' ones. > > Exploiting the above, syzbot found a way to trigger the following > splat: > > WARNING: CPU: 1 PID: 4242 at net/netfilter/xt_cluster.c:55 > xt_cluster_mt+0x6c1/0x840 net/netfilter/xt_cluster.c:127 > Kernel panic - not syncing: panic_on_warn set ... > > CPU: 1 PID: 4242 Comm: syzkaller027971 Not tainted 4.16.0-rc2+ #243 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:17 [inline] > dump_stack+0x194/0x24d lib/dump_stack.c:53 > panic+0x1e4/0x41c kernel/panic.c:183 > __warn+0x1dc/0x200 kernel/panic.c:547 > report_bug+0x211/0x2d0 lib/bug.c:184 > fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178 > fixup_bug arch/x86/kernel/traps.c:247 [inline] > do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296 > do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315 > invalid_op+0x58/0x80 arch/x86/entry/entry_64.S:957 > RIP: 0010:xt_cluster_hash net/netfilter/xt_cluster.c:55 [inline] > RIP: 0010:xt_cluster_mt+0x6c1/0x840 net/netfilter/xt_cluster.c:127 > RSP: 0018:ffff8801d2f6f2d0 EFLAGS: 00010293 > RAX: ffff8801af700540 RBX: 0000000000000000 RCX: ffffffff84a2d1e1 > RDX: 0000000000000000 RSI: ffff8801d2f6f478 RDI: ffff8801cafd336a > RBP: ffff8801d2f6f2e8 R08: 0000000000000000 R09: 0000000000000001 > R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b03b3d18 > R13: ffff8801cafd3300 R14: dffffc0000000000 R15: ffff8801d2f6f478 > ipt_do_table+0xa91/0x19b0 net/ipv4/netfilter/ip_tables.c:296 > iptable_filter_hook+0x65/0x80 net/ipv4/netfilter/iptable_filter.c:41 > nf_hook_entry_hookfn include/linux/netfilter.h:120 [inline] > nf_hook_slow+0xba/0x1a0 net/netfilter/core.c:483 > nf_hook include/linux/netfilter.h:243 [inline] > NF_HOOK include/linux/netfilter.h:286 [inline] > raw_send_hdrinc.isra.17+0xf39/0x1880 net/ipv4/raw.c:432 > raw_sendmsg+0x14cd/0x26b0 net/ipv4/raw.c:669 > inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763 > sock_sendmsg_nosec net/socket.c:629 [inline] > sock_sendmsg+0xca/0x110 net/socket.c:639 > SYSC_sendto+0x361/0x5c0 net/socket.c:1748 > SyS_sendto+0x40/0x50 net/socket.c:1716 > do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287 > entry_SYSCALL_64_after_hwframe+0x42/0xb7 > RIP: 0033:0x441b49 > RSP: 002b:00007ffff5ca8b18 EFLAGS: 00000216 ORIG_RAX: 000000000000002c > RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000441b49 > RDX: 0000000000000030 RSI: 0000000020ff7000 RDI: 0000000000000003 > RBP: 00000000006cc018 R08: 000000002066354c R09: 0000000000000010 > R10: 0000000000000000 R11: 0000000000000216 R12: 0000000000403470 > R13: 0000000000403500 R14: 0000000000000000 R15: 0000000000000000 > Dumping ftrace buffer: > (ftrace buffer empty) > Kernel Offset: disabled > Rebooting in 86400 seconds.. > > Instead of adding checks for template ct on every target/match > manipulating skb->_nfct, simply drop the template ct when skipping > nf_conntrack_in(). Applied, 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
