syzbot


KASAN: use-after-free Read in tipc_mcast_xmit

Status: fixed on 2020/11/28 11:57
Reported-by: syzbot+faf19370eca3f1fd1531@syzkaller.appspotmail.com
Fix commit: 26217e062f97 tipc: fix the skb_unshare() in tipc_buf_append()
First crash: 843d, last: 820d

Fix bisection: fixed by (bisect log) :
commit 26217e062f976fc4e2b7b8b6981a6d119435ea51
Author: Cong Wang <xiyou.wangcong@gmail.com>
Date: Thu Oct 8 04:12:50 2020 +0000

  tipc: fix the skb_unshare() in tipc_buf_append()

similar bugs (3):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-54 KASAN: use-after-free Read in tipc_mcast_xmit C 23 829d 849d 0/2 upstream: reported C repro on 2020/09/29 18:19
upstream KASAN: use-after-free Read in tipc_mcast_xmit (2) C done 37 833d 846d 17/24 fixed on 2020/11/16 12:12
upstream KASAN: use-after-free Read in tipc_mcast_xmit syz 7 1495d 1502d 12/24 fixed on 2019/01/11 01:22

Sample crash report:
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402200
R13: 0000000000402290 R14: 0000000000000000 R15: 0000000000000000
Failed do clone local mcast rcv buffer
==================================================================
BUG: KASAN: use-after-free in __skb_unlink include/linux/skbuff.h:1911 [inline]
BUG: KASAN: use-after-free in __skb_dequeue include/linux/skbuff.h:1931 [inline]
BUG: KASAN: use-after-free in __skb_queue_purge include/linux/skbuff.h:2648 [inline]
BUG: KASAN: use-after-free in tipc_mcast_xmit+0x89f/0x950 net/tipc/bcast.c:322
Read of size 8 at addr ffff8880901faa80 by task syz-executor873/6490

CPU: 1 PID: 6490 Comm: syz-executor873 Not tainted 4.19.149-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+0x22c/0x33e lib/dump_stack.c:118
 print_address_description.cold+0x56/0x25c mm/kasan/report.c:256
 kasan_report_error.cold+0x66/0xb9 mm/kasan/report.c:354
 kasan_report mm/kasan/report.c:412 [inline]
 __asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433
 __skb_unlink include/linux/skbuff.h:1911 [inline]
 __skb_dequeue include/linux/skbuff.h:1931 [inline]
 __skb_queue_purge include/linux/skbuff.h:2648 [inline]
 tipc_mcast_xmit+0x89f/0x950 net/tipc/bcast.c:322
 tipc_sendmcast+0xa90/0xc10 net/tipc/socket.c:808
 __tipc_sendmsg+0xe82/0x1320 net/tipc/socket.c:1342
 tipc_sendmsg+0x4c/0x70 net/tipc/socket.c:1276
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg+0xc7/0x130 net/socket.c:632
 ___sys_sendmsg+0x7bb/0x8f0 net/socket.c:2115
 __sys_sendmsg net/socket.c:2153 [inline]
 __do_sys_sendmsg net/socket.c:2162 [inline]
 __se_sys_sendmsg net/socket.c:2160 [inline]
 __x64_sys_sendmsg+0x132/0x220 net/socket.c:2160
 do_syscall_64+0xf9/0x670 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441339
Code: e8 5c ae 02 00 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 3b 0a fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fffb68f1ce8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441339
RDX: 0000000000000000 RSI: 0000000020000380 RDI: 0000000000000004
RBP: 00000000006cd018 R08: 0000000000000001 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402200
R13: 0000000000402290 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6490:
 kmem_cache_alloc_node+0x146/0x4d0 mm/slab.c:3649
 __alloc_skb+0x71/0x580 net/core/skbuff.c:193
 alloc_skb_fclone include/linux/skbuff.h:1037 [inline]
 tipc_buf_acquire+0x28/0xf0 net/tipc/msg.c:66
 tipc_msg_build+0x686/0x1040 net/tipc/msg.c:309
 tipc_sendmcast+0x901/0xc10 net/tipc/socket.c:804
 __tipc_sendmsg+0xe82/0x1320 net/tipc/socket.c:1342
 tipc_sendmsg+0x4c/0x70 net/tipc/socket.c:1276
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg+0xc7/0x130 net/socket.c:632
 ___sys_sendmsg+0x7bb/0x8f0 net/socket.c:2115
 __sys_sendmsg net/socket.c:2153 [inline]
 __do_sys_sendmsg net/socket.c:2162 [inline]
 __se_sys_sendmsg net/socket.c:2160 [inline]
 __x64_sys_sendmsg+0x132/0x220 net/socket.c:2160
 do_syscall_64+0xf9/0x670 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 6490:
 __cache_free mm/slab.c:3503 [inline]
 kmem_cache_free+0x7f/0x2b0 mm/slab.c:3765
 kfree_skbmem+0xa4/0x140 net/core/skbuff.c:607
 __kfree_skb net/core/skbuff.c:646 [inline]
 kfree_skb+0x127/0x3f0 net/core/skbuff.c:663
 tipc_buf_append+0x655/0xc30 net/tipc/msg.c:188
 tipc_msg_reassemble+0x175/0x4f0 net/tipc/msg.c:649
 tipc_mcast_xmit+0x34d/0x950 net/tipc/bcast.c:305
 tipc_sendmcast+0xa90/0xc10 net/tipc/socket.c:808
 __tipc_sendmsg+0xe82/0x1320 net/tipc/socket.c:1342
 tipc_sendmsg+0x4c/0x70 net/tipc/socket.c:1276
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg+0xc7/0x130 net/socket.c:632
 ___sys_sendmsg+0x7bb/0x8f0 net/socket.c:2115
 __sys_sendmsg net/socket.c:2153 [inline]
 __do_sys_sendmsg net/socket.c:2162 [inline]
 __se_sys_sendmsg net/socket.c:2160 [inline]
 __x64_sys_sendmsg+0x132/0x220 net/socket.c:2160
 do_syscall_64+0xf9/0x670 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880901faa80
 which belongs to the cache skbuff_fclone_cache of size 472
The buggy address is located 0 bytes inside of
 472-byte region [ffff8880901faa80, ffff8880901fac58)
The buggy address belongs to the page:
page:ffffea0002407e80 count:1 mapcount:0 mapping:ffff88821b6af9c0 index:0x0
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffffea0002788008 ffff8880a9b5e448 ffff88821b6af9c0
raw: 0000000000000000 ffff8880901fa080 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880901fa980: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
 ffff8880901faa00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880901faa80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8880901fab00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880901fab80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (3):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets Title
ci2-linux-4-19 2020/10/05 11:47 linux-4.19.y b09c34517e1a 5ef9c291 .config console log report syz C
ci2-linux-4-19 2020/10/28 20:13 linux-4.19.y ad326970d25c f24824d3 .config console log report info
ci2-linux-4-19 2020/10/05 11:34 linux-4.19.y b09c34517e1a 5ef9c291 .config console log report info
* Struck through repros no longer work on HEAD.