Subject: Re: KASAN: use-after-free Read in __nf_tables_abort

From: syzbot <[email-masked]>
Date: Tue, 21 Jan 2020 04:37:09 -0800

syzbot has found a reproducer for the following crash on:

HEAD commit:    d96d875e Merge tag 'fixes_for_v5.5-rc8' of git://git.kerne..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10cd81c9e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=83c00afca9cf5153
dashboard link: https://syzkaller.appspot.com/bug?extid=29125d208b3dae9a7019
compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1203f521e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10a706a5e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]

==================================================================
BUG: KASAN: use-after-free in __list_del_entry_valid+0x2f/0x100 lib/list_debug.c:42
Read of size 8 at addr ffff888097973008 by task syz-executor694/8782

CPU: 1 PID: 8782 Comm: syz-executor694 Not tainted 5.5.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fb/0x318 lib/dump_stack.c:118
 print_address_description+0x74/0x5c0 mm/kasan/report.c:374
 __kasan_report+0x149/0x1c0 mm/kasan/report.c:506
 kasan_report+0x26/0x50 mm/kasan/common.c:639
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
 __list_del_entry_valid+0x2f/0x100 lib/list_debug.c:42
 __list_del_entry include/linux/list.h:131 [inline]
 list_del_rcu include/linux/rculist.h:148 [inline]
 __nf_tables_abort+0x16d2/0x2e80 net/netfilter/nf_tables_api.c:7258
 nf_tables_abort+0x15/0x30 net/netfilter/nf_tables_api.c:7373
 nfnetlink_rcv_batch net/netfilter/nfnetlink.c:494 [inline]
 nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:543 [inline]
 nfnetlink_rcv+0x1a88/0x1e50 net/netfilter/nfnetlink.c:561
 netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
 netlink_unicast+0x767/0x920 net/netlink/af_netlink.c:1328
 netlink_sendmsg+0xa2c/0xd50 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:639 [inline]
 sock_sendmsg net/socket.c:659 [inline]
 ____sys_sendmsg+0x4f7/0x7f0 net/socket.c:2330
 ___sys_sendmsg net/socket.c:2384 [inline]
 __sys_sendmsg+0x1ed/0x290 net/socket.c:2417
 __do_sys_sendmsg net/socket.c:2426 [inline]
 __se_sys_sendmsg net/socket.c:2424 [inline]
 __x64_sys_sendmsg+0x7f/0x90 net/socket.c:2424
 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4470c9
Code: e8 dc e6 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 0f 83 2b 06 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffb4f1fad98 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000006dcc28 RCX: 00000000004470c9
RDX: 0000000000000000 RSI: 0000000020000280 RDI: 0000000000000003
RBP: 00000000006dcc20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dcc2c
R13: 00000000200002c0 R14: 00000000004af6c8 R15: 0000000000000000

Allocated by task 8782:
 save_stack mm/kasan/common.c:72 [inline]
 set_track mm/kasan/common.c:80 [inline]
 __kasan_kmalloc+0x118/0x1c0 mm/kasan/common.c:513
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:527
 kmem_cache_alloc_trace+0x221/0x2f0 mm/slab.c:3551
 kmalloc include/linux/slab.h:556 [inline]
 kzalloc include/linux/slab.h:670 [inline]
 nf_tables_newtable+0x350/0x1b10 net/netfilter/nf_tables_api.c:981
 nfnetlink_rcv_batch net/netfilter/nfnetlink.c:433 [inline]
 nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:543 [inline]
 nfnetlink_rcv+0xecf/0x1e50 net/netfilter/nfnetlink.c:561
 netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
 netlink_unicast+0x767/0x920 net/netlink/af_netlink.c:1328
 netlink_sendmsg+0xa2c/0xd50 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:639 [inline]
 sock_sendmsg net/socket.c:659 [inline]
 ____sys_sendmsg+0x4f7/0x7f0 net/socket.c:2330
 ___sys_sendmsg net/socket.c:2384 [inline]
 __sys_sendmsg+0x1ed/0x290 net/socket.c:2417
 __do_sys_sendmsg net/socket.c:2426 [inline]
 __se_sys_sendmsg net/socket.c:2424 [inline]
 __x64_sys_sendmsg+0x7f/0x90 net/socket.c:2424
 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 2679:
 save_stack mm/kasan/common.c:72 [inline]
 set_track mm/kasan/common.c:80 [inline]
 kasan_set_free_info mm/kasan/common.c:335 [inline]
 __kasan_slab_free+0x12e/0x1e0 mm/kasan/common.c:474
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:483
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10d/0x220 mm/slab.c:3757
 nft_commit_release net/netfilter/nf_tables_api.c:2496 [inline]
 nf_tables_trans_destroy_work+0x9b8/0xbb0 net/netfilter/nf_tables_api.c:6860
 process_one_work+0x7f5/0x10d0 kernel/workqueue.c:2264
 worker_thread+0xbbc/0x1630 kernel/workqueue.c:2410
 kthread+0x332/0x350 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff888097973000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 8 bytes inside of
 512-byte region [ffff888097973000, ffff888097973200)
The buggy address belongs to the page:
page:ffffea00025e5cc0 refcount:1 mapcount:0 mapping:ffff8880aa800a80 index:0x0
raw: 00fffe0000000200 ffffea0002a53ac8 ffffea0002806848 ffff8880aa800a80
raw: 0000000000000000 ffff888097973000 0000000100000004 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888097972f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888097972f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888097973000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff888097973080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888097973100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================