Re: [syzbot] [net?] KASAN: use-after-free Read in __skb_flow_dissect (3)

[syzbot <syzbot+bfde3bef047a81b8fde6@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: use-after-free Read in get_l4proto

==================================================================
BUG: KASAN: use-after-free in ipv4_get_l4proto net/netfilter/nf_conntrack_core.c:358 [inline]
BUG: KASAN: use-after-free in get_l4proto+0x3f6/0x520 net/netfilter/nf_conntrack_core.c:407
Read of size 2 at addr ffff88813d810000 by task syz-executor.0/5510

CPU: 2 PID: 5510 Comm: syz-executor.0 Not tainted 6.7.0-syzkaller-g296455ade1fd-dirty #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0xc4/0x620 mm/kasan/report.c:488
 kasan_report+0xda/0x110 mm/kasan/report.c:601
 ipv4_get_l4proto net/netfilter/nf_conntrack_core.c:358 [inline]
 get_l4proto+0x3f6/0x520 net/netfilter/nf_conntrack_core.c:407
 nf_conntrack_in+0x1e3/0x1850 net/netfilter/nf_conntrack_core.c:1977
 ipv4_conntrack_local+0x160/0x260 net/netfilter/nf_conntrack_proto.c:229
 nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline]
 nf_hook_slow+0xbb/0x1f0 net/netfilter/core.c:626
 nf_hook+0x386/0x6c0 include/linux/netfilter.h:269
 __ip_local_out+0x33b/0x640 net/ipv4/ip_output.c:118
 ip_local_out+0x2a/0x1a0 net/ipv4/ip_output.c:127
 iptunnel_xmit+0x5b4/0x9b0 net/ipv4/ip_tunnel_core.c:82
 ip_tunnel_xmit+0x1daa/0x33b0 net/ipv4/ip_tunnel.c:831
 ipip_tunnel_xmit+0x3cc/0x4e0 net/ipv4/ipip.c:308
 __netdev_start_xmit include/linux/netdevice.h:4989 [inline]
 netdev_start_xmit include/linux/netdevice.h:5003 [inline]
 xmit_one net/core/dev.c:3547 [inline]
 dev_hard_start_xmit+0x137/0x6d0 net/core/dev.c:3563
 __dev_queue_xmit+0x7b6/0x3ed0 net/core/dev.c:4351
 dev_queue_xmit include/linux/netdevice.h:3171 [inline]
 neigh_connected_output+0x426/0x5d0 net/core/neighbour.c:1592
 neigh_output include/net/neighbour.h:542 [inline]
 ip_finish_output2+0x82d/0x2540 net/ipv4/ip_output.c:235
 __ip_finish_output net/ipv4/ip_output.c:313 [inline]
 __ip_finish_output+0x38b/0x650 net/ipv4/ip_output.c:295
 ip_finish_output+0x31/0x310 net/ipv4/ip_output.c:323
 NF_HOOK_COND include/linux/netfilter.h:303 [inline]
 ip_mc_output+0x1dd/0x6a0 net/ipv4/ip_output.c:420
 dst_output include/net/dst.h:451 [inline]
 ip_local_out+0xaf/0x1a0 net/ipv4/ip_output.c:129
 iptunnel_xmit+0x5b4/0x9b0 net/ipv4/ip_tunnel_core.c:82
 ip_tunnel_xmit+0x1daa/0x33b0 net/ipv4/ip_tunnel.c:831
 ipgre_xmit+0x49b/0x980 net/ipv4/ip_gre.c:665
 __netdev_start_xmit include/linux/netdevice.h:4989 [inline]
 netdev_start_xmit include/linux/netdevice.h:5003 [inline]
 xmit_one net/core/dev.c:3547 [inline]
 dev_hard_start_xmit+0x137/0x6d0 net/core/dev.c:3563
 __dev_queue_xmit+0x7b6/0x3ed0 net/core/dev.c:4351
 dev_queue_xmit include/linux/netdevice.h:3171 [inline]
 __bpf_tx_skb net/core/filter.c:2135 [inline]
 __bpf_redirect_no_mac net/core/filter.c:2165 [inline]
 __bpf_redirect+0x6f1/0xf10 net/core/filter.c:2188
 ____bpf_clone_redirect net/core/filter.c:2459 [inline]
 bpf_clone_redirect+0x2b2/0x420 net/core/filter.c:2431
 ___bpf_prog_run+0x3e44/0xabc0 kernel/bpf/core.c:1986
 __bpf_prog_run512+0xb7/0xf0 kernel/bpf/core.c:2227
 bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline]
 __bpf_prog_run include/linux/filter.h:651 [inline]
 bpf_prog_run include/linux/filter.h:658 [inline]
 bpf_test_run+0x3d3/0x9c0 net/bpf/test_run.c:423
 bpf_prog_test_run_skb+0xb75/0x1dd0 net/bpf/test_run.c:1056
 bpf_prog_test_run kernel/bpf/syscall.c:4107 [inline]
 __sys_bpf+0x11bf/0x4a00 kernel/bpf/syscall.c:5475
 __do_sys_bpf kernel/bpf/syscall.c:5561 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5559 [inline]
 __x64_sys_bpf+0x78/0xc0 kernel/bpf/syscall.c:5559
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xd3/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f69b887cce9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f69b958b0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f69b899bf80 RCX: 00007f69b887cce9
RDX: 0000000000000028 RSI: 0000000020000080 RDI: 000000000000000a
RBP: 00007f69b88c947a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f69b899bf80 R15: 00007fffebba7a48
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0004f60400 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x13d810
flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 057ff00000000000 ffffea0004f60408 ffffea0004f60408 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffff88813d80ff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88813d80ff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88813d810000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff88813d810080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88813d810100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


Tested on:

commit:         296455ad Merge tag 'char-misc-6.8-rc1' of git://git.ke..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=156f278fe80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e5a3077efcfd8745
dashboard link: https://syzkaller.appspot.com/bug?extid=bfde3bef047a81b8fde6
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=17d251b3e80000