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commit aebfa52a925d701114afd6af0def35bab16d4f47 upstream. 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(). Fixes: 7b4fdf77a450ec ("netfilter: don't track fragmented packets") Reported-and-tested-by: syzbot+0346441ae0545cfcea3a@syzkaller.appspotmail.com Signed-off-by: Paolo Abeni <pabeni@redhat.com> Acked-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.