KASAN: use-after-free Read in route4_get

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 339485c9 Linux 4.19.110
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1017ffdde00000
kernel config: https://syzkaller.appspot.com/x/.config?x=8d390b1a40a32588
dashboard link: https://syzkaller.appspot.com/bug?extid=a78eaa6233f0d1a17127
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a78eaa...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in route4_get+0x3e1/0x420 net/sched/cls_route.c:239
Read of size 4 at addr ffff888041e37c40 by task syz-executor.5/27529

CPU: 0 PID: 27529 Comm: syz-executor.5 Not tainted 4.19.110-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+0x188/0x20d lib/dump_stack.c:118
print_address_description.cold+0x7c/0x212 mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report mm/kasan/report.c:412 [inline]
kasan_report.cold+0x88/0x2b9 mm/kasan/report.c:396
route4_get+0x3e1/0x420 net/sched/cls_route.c:239
tc_new_tfilter+0x509/0x1450 net/sched/cls_api.c:1300
rtnetlink_rcv_msg+0x453/0xaf0 net/core/rtnetlink.c:4777
netlink_rcv_skb+0x160/0x410 net/netlink/af_netlink.c:2455
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x4d7/0x6a0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x80b/0xcd0 net/netlink/af_netlink.c:1909
sock_sendmsg_nosec net/socket.c:622 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:632
___sys_sendmsg+0x803/0x920 net/socket.c:2115
__sys_sendmsg+0xec/0x1b0 net/socket.c:2153
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c849
Code: ad b6 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007eff6d87ec78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007eff6d87f6d4 RCX: 000000000045c849
RDX: 0000000000000000 RSI: 0000000020000280 RDI: 0000000000000007
RBP: 000000000076bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000009fa R14: 00000000004ccb28 R15: 000000000076bfac

Allocated by task 27413:
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc mm/kasan/kasan.c:553 [inline]
kasan_kmalloc+0xbf/0xe0 mm/kasan/kasan.c:531
kmem_cache_alloc_trace+0x14d/0x7a0 mm/slab.c:3625
kmalloc include/linux/slab.h:515 [inline]
kzalloc include/linux/slab.h:709 [inline]
route4_change+0x2a5/0x2210 net/sched/cls_route.c:495
tc_new_tfilter+0xa6b/0x1450 net/sched/cls_api.c:1320
rtnetlink_rcv_msg+0x453/0xaf0 net/core/rtnetlink.c:4777
netlink_rcv_skb+0x160/0x410 net/netlink/af_netlink.c:2455
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x4d7/0x6a0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x80b/0xcd0 net/netlink/af_netlink.c:1909
sock_sendmsg_nosec net/socket.c:622 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:632
___sys_sendmsg+0x803/0x920 net/socket.c:2115
__sys_sendmsg+0xec/0x1b0 net/socket.c:2153
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 457:
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0xf7/0x140 mm/kasan/kasan.c:521
__cache_free mm/slab.c:3503 [inline]
kfree+0xce/0x220 mm/slab.c:3822
route4_delete_filter_work+0x17/0x20 net/sched/cls_route.c:270
process_one_work+0x91f/0x1640 kernel/workqueue.c:2153
worker_thread+0x96/0xe20 kernel/workqueue.c:2296
kthread+0x34a/0x420 kernel/kthread.c:246
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

The buggy address belongs to the object at ffff888041e37c00
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 64 bytes inside of
192-byte region [ffff888041e37c00, ffff888041e37cc0)
The buggy address belongs to the page:
page:ffffea0001078dc0 count:1 mapcount:0 mapping:ffff88812c3dc040 index:0x0
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffffea000147d908 ffff88812c3d4148 ffff88812c3dc040
raw: 0000000000000000 ffff888041e37000 0000000100000010 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888041e37b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888041e37b80: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
>ffff888041e37c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888041e37c80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff888041e37d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================
audit: type=1800 audit(1584459291.234:387): pid=28111 uid=0 auid=4294967295 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 op=collect_data cause=failed comm="syz-executor.0" name="SYSV00000000" dev="hugetlbfs" ino=7012437 res=0


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[syzbot]

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