KASAN: use-after-free Read in tcindex_dump

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: c2003765 Merge tag 'io_uring-5.6-2020-03-07' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1275b731e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=4527d1e2fb19fd5c
dashboard link: https://syzkaller.appspot.com/bug?extid=653090db2562495901dc
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1180ff29e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+653090...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in tcindex_dump+0xb6e/0xc20 net/sched/cls_tcindex.c:637
Read of size 8 at addr ffff88807ebd0020 by task syz-executor.3/10006

CPU: 0 PID: 10006 Comm: syz-executor.3 Not tainted 5.6.0-rc4-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.constprop.0.cold+0xd3/0x315 mm/kasan/report.c:374
__kasan_report.cold+0x1a/0x32 mm/kasan/report.c:506
kasan_report+0xe/0x20 mm/kasan/common.c:641
tcindex_dump+0xb6e/0xc20 net/sched/cls_tcindex.c:637
tcf_fill_node+0x572/0x930 net/sched/cls_api.c:1814
tfilter_notify+0x139/0x2a0 net/sched/cls_api.c:1840
tc_new_tfilter+0xab2/0x20b0 net/sched/cls_api.c:2107
rtnetlink_rcv_msg+0x810/0xad0 net/core/rtnetlink.c:5427
netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2478
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6b9/0x7d0 net/socket.c:2343
___sys_sendmsg+0x100/0x170 net/socket.c:2397
__sys_sendmsg+0xec/0x1b0 net/socket.c:2430
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c4a9
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:00007fb7e5f98c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fb7e5f996d4 RCX: 000000000045c4a9
RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000000000004
RBP: 000000000076bfc0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000009fa R14: 00000000004cc777 R15: 000000000076bfcc

Allocated by task 10000:
save_stack+0x1b/0x80 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
__kasan_kmalloc mm/kasan/common.c:515 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:488
__do_kmalloc mm/slab.c:3656 [inline]
__kmalloc+0x161/0x7a0 mm/slab.c:3665
kmalloc_array include/linux/slab.h:597 [inline]
kcalloc include/linux/slab.h:608 [inline]
tcindex_alloc_perfect_hash+0x5a/0x320 net/sched/cls_tcindex.c:281
tcindex_set_parms+0x1568/0x1a00 net/sched/cls_tcindex.c:405
tcindex_change+0x203/0x2e0 net/sched/cls_tcindex.c:518
tc_new_tfilter+0xa59/0x20b0 net/sched/cls_api.c:2103
rtnetlink_rcv_msg+0x810/0xad0 net/core/rtnetlink.c:5427
netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2478
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6b9/0x7d0 net/socket.c:2343
___sys_sendmsg+0x100/0x170 net/socket.c:2397
__sys_sendmsg+0xec/0x1b0 net/socket.c:2430
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 262:
save_stack+0x1b/0x80 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
kasan_set_free_info mm/kasan/common.c:337 [inline]
__kasan_slab_free+0xf7/0x140 mm/kasan/common.c:476
__cache_free mm/slab.c:3426 [inline]
kfree+0x109/0x2b0 mm/slab.c:3757
tcindex_partial_destroy_work+0x2e/0x50 net/sched/cls_tcindex.c:264
process_one_work+0x94b/0x1690 kernel/workqueue.c:2264
worker_thread+0x96/0xe20 kernel/workqueue.c:2410
kthread+0x357/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff88807ebd0000
which belongs to the cache kmalloc-16k of size 16384
The buggy address is located 32 bytes inside of
16384-byte region [ffff88807ebd0000, ffff88807ebd4000)
The buggy address belongs to the page:
page:ffffea0001faf400 refcount:1 mapcount:0 mapping:ffff8880aa002380 index:0x0 compound_mapcount: 0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea0001faf208 ffffea0001faf608 ffff8880aa002380
raw: 0000000000000000 ffff88807ebd0000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88807ebcff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88807ebcff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc


---
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syzbot can test patches for this bug, for details see:
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[Cong Wang]

#syz test: https://github.com/congwang/linux.git tcindex

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger crash:

Reported-and-tested-by: syzbot+653090...@syzkaller.appspotmail.com

Tested on:

commit: 2c19e526 net_sched: hold rtnl lock for tcindex_partial_des..
git tree: https://github.com/congwang/linux.git tcindex
kernel config: https://syzkaller.appspot.com/x/.config?x=bcbe864577669742

dashboard link: https://syzkaller.appspot.com/bug?extid=653090db2562495901dc
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Note: testing is done by a robot and is best-effort only.

[Cong Wang]

#syz fix: net_sched: hold rtnl lock in tcindex_partial_destroy_work()