KASAN: use-after-free Read in tipc_mcast_xmit

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: b09c3451 Linux 4.19.149
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1736493f900000
kernel config: https://syzkaller.appspot.com/x/.config?x=d7c6dfb55644e8fd
dashboard link: https://syzkaller.appspot.com/bug?extid=faf19370eca3f1fd1531
compiler: gcc (GCC) 10.1.0-syz 20200507

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+faf193...@syzkaller.appspotmail.com

RBP: 00007fbb063d8ca0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000005
R13: 00007ffc738276cf R14: 00007fbb063d99c0 R15: 000000000118bf2c
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 ffff888090bd8540 by task syz-executor.5/12801

CPU: 0 PID: 12801 Comm: syz-executor.5 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: 0033:0x45de89
Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fbb063d8c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000002e740 RCX: 000000000045de89
RDX: 0000000000000000 RSI: 0000000020000380 RDI: 0000000000000003
RBP: 00007fbb063d8ca0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000005
R13: 00007ffc738276cf R14: 00007fbb063d99c0 R15: 000000000118bf2c

Allocated by task 12801:
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 12801:
__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 ffff888090bd8540
which belongs to the cache skbuff_fclone_cache of size 472
The buggy address is located 0 bytes inside of
472-byte region [ffff888090bd8540, ffff888090bd8718)
The buggy address belongs to the page:
page:ffffea000242f600 count:1 mapcount:0 mapping:ffff8880a999f900 index:0x0
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffffea0001931f08 ffffea000251a948 ffff8880a999f900
raw: 0000000000000000 ffff888090bd8040 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888090bd8400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888090bd8480: fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888090bd8500: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
^
ffff888090bd8580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888090bd8600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: b09c3451 Linux 4.19.149
git tree: linux-4.19.y

console output: https://syzkaller.appspot.com/x/log.txt?x=144ec7a3900000

kernel config: https://syzkaller.appspot.com/x/.config?x=d7c6dfb55644e8fd
dashboard link: https://syzkaller.appspot.com/bug?extid=faf19370eca3f1fd1531
compiler: gcc (GCC) 10.1.0-syz 20200507

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1273631f900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=149ea750500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+faf193...@syzkaller.appspotmail.com

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
==================================================================

[syzbot]

syzbot suspects this issue was fixed by commit:

commit 26217e062f976fc4e2b7b8b6981a6d119435ea51
Author: Cong Wang <xiyou.w...@gmail.com>
Date: Thu Oct 8 04:12:50 2020 +0000

tipc: fix the skb_unshare() in tipc_buf_append()

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10cf9979500000
start commit: b09c3451 Linux 4.19.149
git tree: linux-4.19.y

kernel config: https://syzkaller.appspot.com/x/.config?x=d7c6dfb55644e8fd
dashboard link: https://syzkaller.appspot.com/bug?extid=faf19370eca3f1fd1531

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1273631f900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=149ea750500000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: tipc: fix the skb_unshare() in tipc_buf_append()

For information about bisection process see: https://goo.gl/tpsmEJ#bisection