Date: Mon, 01 Jan 2024 09:18:16 -0800
From: syzbot <syzbot+bfde3bef047a81b8fde6@...kaller.appspotmail.com>
To: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org, pabeni@...hat.com, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [net?] KASAN: use-after-free Read in __skb_flow_dissect (3)

Hello,

syzbot found the following issue on:

HEAD commit:    f5837722ffec Merge tag 'mm-hotfixes-stable-2023-12-27-15-0..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1650e3d9e80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=da1c95d4e55dda83
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
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17e61d95e80000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=122dfc65e80000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-f5837722.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/148f0f94b7b6/vmlinux-f5837722.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d63ba20405f3/bzImage-f5837722.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bfde3bef047a81b8fde6@...kaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170
Read of size 1 at addr ffff88812fb4000e by task syz-executor183/5191

CPU: 1 PID: 5191 Comm: syz-executor183 Not tainted 6.7.0-rc7-syzkaller-00016-gf5837722ffec #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:364 [inline]
 print_report+0xc4/0x620 mm/kasan/report.c:475
 kasan_report+0xda/0x110 mm/kasan/report.c:588
 __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170
 skb_flow_dissect_flow_keys include/linux/skbuff.h:1514 [inline]
 ___skb_get_hash net/core/flow_dissector.c:1791 [inline]
 __skb_get_hash+0xc7/0x540 net/core/flow_dissector.c:1856
 skb_get_hash include/linux/skbuff.h:1556 [inline]
 ip_tunnel_xmit+0x1855/0x33c0 net/ipv4/ip_tunnel.c:748
 ipip_tunnel_xmit+0x3cc/0x4e0 net/ipv4/ipip.c:308
 __netdev_start_xmit include/linux/netdevice.h:4940 [inline]
 netdev_start_xmit include/linux/netdevice.h:4954 [inline]
 xmit_one net/core/dev.c:3548 [inline]
 dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564
 __dev_queue_xmit+0x7c1/0x3d60 net/core/dev.c:4349
 dev_queue_xmit include/linux/netdevice.h:3134 [inline]
 neigh_connected_output+0x42c/0x5d0 net/core/neighbour.c:1592
 neigh_output include/net/neighbour.h:542 [inline]
 ip_finish_output2+0x833/0x2550 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+0x1dbc/0x33c0 net/ipv4/ip_tunnel.c:831
 ipgre_xmit+0x4a1/0x980 net/ipv4/ip_gre.c:665
 __netdev_start_xmit include/linux/netdevice.h:4940 [inline]
 netdev_start_xmit include/linux/netdevice.h:4954 [inline]
 xmit_one net/core/dev.c:3548 [inline]
 dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564
 __dev_queue_xmit+0x7c1/0x3d60 net/core/dev.c:4349
 dev_queue_xmit include/linux/netdevice.h:3134 [inline]
 __bpf_tx_skb net/core/filter.c:2133 [inline]
 __bpf_redirect_no_mac net/core/filter.c:2163 [inline]
 __bpf_redirect+0x6f1/0xf10 net/core/filter.c:2186
 ____bpf_clone_redirect net/core/filter.c:2457 [inline]
 bpf_clone_redirect+0x2b2/0x420 net/core/filter.c:2429
 ___bpf_prog_run+0x3e44/0xabc0 kernel/bpf/core.c:1962
 __bpf_prog_run512+0xb7/0xf0 kernel/bpf/core.c:2203
 bpf_dispatcher_nop_func include/linux/bpf.h:1196 [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:1045
 bpf_prog_test_run kernel/bpf/syscall.c:4040 [inline]
 __sys_bpf+0x11bf/0x4910 kernel/bpf/syscall.c:5401
 __do_sys_bpf kernel/bpf/syscall.c:5487 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5485 [inline]
 __x64_sys_bpf+0x78/0xc0 kernel/bpf/syscall.c:5485
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f8b086e9d69
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 19 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff09b0b818 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f8b086e9d69
RDX: 0000000000000028 RSI: 0000000020000080 RDI: 000000000000000a
RBP: 0000000000000000 R08: 0000000100000000 R09: 0000000100000000
R10: 0000000100000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0004bed000 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12fb40
flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 057ff00000000000 ffffea0004bed008 ffffea0004bed008 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:
 ffff88812fb3ff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812fb3ff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88812fb40000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff88812fb40080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812fb40100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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