KASAN: use-after-free Read in tcf_block_put

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c4ff839d Linux 4.19.171
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10ec30c4d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=811800d94e12c69
dashboard link: https://syzkaller.appspot.com/bug?extid=4265191aa48257485199
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+426519...@syzkaller.appspotmail.com

2097051 pages RAM
0 pages HighMem/MovableOnly
369638 pages reserved
0 pages cma reserved
==================================================================
BUG: KASAN: use-after-free in tcf_block_put+0xf6/0x100 net/sched/cls_api.c:797
Read of size 8 at addr ffff8880583d9ce0 by task syz-executor.0/26979

CPU: 1 PID: 26979 Comm: syz-executor.0 Not tainted 4.19.171-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+0x1fc/0x2ef lib/dump_stack.c:118
print_address_description.cold+0x54/0x219 mm/kasan/report.c:256
kasan_report_error.cold+0x8a/0x1b9 mm/kasan/report.c:354
kasan_report mm/kasan/report.c:412 [inline]
__asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433
tcf_block_put+0xf6/0x100 net/sched/cls_api.c:797
cake_destroy+0x3f/0x80 net/sched/sch_cake.c:2630
qdisc_create+0xb70/0x1130 net/sched/sch_api.c:1204
tc_modify_qdisc+0x50d/0x1a80 net/sched/sch_api.c:1572
rtnetlink_rcv_msg+0x453/0xb80 net/core/rtnetlink.c:4778
netlink_rcv_skb+0x160/0x440 net/netlink/af_netlink.c:2455
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x4d5/0x690 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x6bb/0xc40 net/netlink/af_netlink.c:1909
sock_sendmsg_nosec net/socket.c:622 [inline]
sock_sendmsg+0xc3/0x120 net/socket.c:632
___sys_sendmsg+0x7bb/0x8e0 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+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45e219
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:00007f0938bacc68 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 000000000045e219
RDX: 0000000000000000 RSI: 00000000200007c0 RDI: 0000000000000003
RBP: 00007f0938bacca0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000000f
R13: 00007ffd2fe3630f R14: 00007f0938bad9c0 R15: 000000000119bf8c

Allocated by task 26979:
kmem_cache_alloc_trace+0x12f/0x380 mm/slab.c:3625
kmalloc include/linux/slab.h:515 [inline]
kzalloc include/linux/slab.h:709 [inline]
tcf_block_create net/sched/cls_api.c:505 [inline]
tcf_block_get_ext+0x26a/0x13b0 net/sched/cls_api.c:680
tcf_block_get+0xa9/0xf0 net/sched/cls_api.c:742
cake_init+0x2c9/0xb50 net/sched/sch_cake.c:2663
qdisc_create+0x579/0x1130 net/sched/sch_api.c:1156
tc_modify_qdisc+0x50d/0x1a80 net/sched/sch_api.c:1572
rtnetlink_rcv_msg+0x453/0xb80 net/core/rtnetlink.c:4778
netlink_rcv_skb+0x160/0x440 net/netlink/af_netlink.c:2455
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x4d5/0x690 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x6bb/0xc40 net/netlink/af_netlink.c:1909
sock_sendmsg_nosec net/socket.c:622 [inline]
sock_sendmsg+0xc3/0x120 net/socket.c:632
___sys_sendmsg+0x7bb/0x8e0 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+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 26979:
__cache_free mm/slab.c:3503 [inline]
kfree+0xcc/0x210 mm/slab.c:3822
tcf_block_put_ext.part.0+0x5a1/0x6e0 net/sched/cls_api.c:784
tcf_block_put_ext net/sched/cls_api.c:754 [inline]
tcf_block_put+0xad/0x100 net/sched/cls_api.c:797
cake_destroy net/sched/sch_cake.c:2630 [inline]
cake_init+0xa9a/0xb50 net/sched/sch_cake.c:2706
qdisc_create+0x579/0x1130 net/sched/sch_api.c:1156
tc_modify_qdisc+0x50d/0x1a80 net/sched/sch_api.c:1572
rtnetlink_rcv_msg+0x453/0xb80 net/core/rtnetlink.c:4778
netlink_rcv_skb+0x160/0x440 net/netlink/af_netlink.c:2455
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x4d5/0x690 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x6bb/0xc40 net/netlink/af_netlink.c:1909
sock_sendmsg_nosec net/socket.c:622 [inline]
sock_sendmsg+0xc3/0x120 net/socket.c:632
___sys_sendmsg+0x7bb/0x8e0 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+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880583d9cc0
which belongs to the cache kmalloc-128 of size 128
The buggy address is located 32 bytes inside of
128-byte region [ffff8880583d9cc0, ffff8880583d9d40)
The buggy address belongs to the page:
page:ffffea000160f640 count:1 mapcount:0 mapping:ffff88813bff0640 index:0x0
flags: 0xfff00000000100(slab)
raw: 00fff00000000100 ffffea000122e648 ffff88813bff1548 ffff88813bff0640
raw: 0000000000000000 ffff8880583d9000 0000000100000015 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880583d9b80: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
ffff8880583d9c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880583d9c80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
^
ffff8880583d9d00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8880583d9d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.