KASAN: use-after-free Write in tcindex_set_parms

From: syzbot
Date: Tue Mar 10 2020 - 18:15:19 EST

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Hello,

syzbot found the following crash on:

HEAD commit: 30bb5572 Merge tag 'ktest-v5.6' of git://git.kernel.org/pu..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15bae581e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=c2e311dba9a02ba9
dashboard link: https://syzkaller.appspot.com/bug?extid=e5db00b3987d59130da5
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11fe8219e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=129e5439e00000

The bug was bisected to:

commit 599be01ee567b61f4471ee8078870847d0a11e8e
Author: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Date: Mon Feb 3 05:14:35 2020 +0000

net_sched: fix an OOB access in cls_tcindex

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=141c1dfde00000
final crash: https://syzkaller.appspot.com/x/report.txt?x=161c1dfde00000
console output: https://syzkaller.appspot.com/x/log.txt?x=121c1dfde00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e5db00b3987d59130da5@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 599be01ee567 ("net_sched: fix an OOB access in cls_tcindex")

IPVS: ftp: loaded support on port[0] = 21
==================================================================
BUG: KASAN: use-after-free in tcindex_set_parms+0x17fd/0x1a00 net/sched/cls_tcindex.c:455
Write of size 16 at addr ffff8880a86d28b8 by task syz-executor352/9506

CPU: 0 PID: 9506 Comm: syz-executor352 Not tainted 5.6.0-rc5-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_set_parms+0x17fd/0x1a00 net/sched/cls_tcindex.c:455
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
RIP: 0033:0x440eb9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 7b 10 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffc66658278 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004a2690 RCX: 0000000000440eb9
RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000000000003
RBP: 00000000004a2690 R08: 0000000120080522 R09: 0000000120080522
R10: 0000000120080522 R11: 0000000000000246 R12: 00000000004023c0
R13: 0000000000402450 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 1:
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
kmem_cache_alloc_trace+0x153/0x7d0 mm/slab.c:3551
kmalloc include/linux/slab.h:555 [inline]
kzalloc include/linux/slab.h:669 [inline]
call_usermodehelper_setup+0x98/0x300 kernel/umh.c:386
kobject_uevent_env+0xcfb/0x11f0 lib/kobject_uevent.c:613
kernel_add_sysfs_param kernel/params.c:797 [inline]
param_sysfs_builtin kernel/params.c:832 [inline]
param_sysfs_init+0x3c5/0x430 kernel/params.c:953
do_one_initcall+0x10a/0x7d0 init/main.c:1152
do_initcall_level init/main.c:1225 [inline]
do_initcalls init/main.c:1241 [inline]
do_basic_setup init/main.c:1261 [inline]
kernel_init_freeable+0x501/0x5ae init/main.c:1445
kernel_init+0xd/0x1bb init/main.c:1352
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Freed by task 562:
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
call_usermodehelper_freeinfo kernel/umh.c:48 [inline]
umh_complete kernel/umh.c:62 [inline]
umh_complete+0x81/0x90 kernel/umh.c:51
call_usermodehelper_exec_async+0x459/0x710 kernel/umh.c:122
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff8880a86d2800
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 184 bytes inside of
192-byte region [ffff8880a86d2800, ffff8880a86d28c0)
The buggy address belongs to the page:
page:ffffea0002a1b480 refcount:1 mapcount:0 mapping:ffff8880aa000000 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00028da348 ffff8880aa001148 ffff8880aa000000
raw: 0000000000000000 ffff8880a86d2000 0000000100000010 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a86d2780: 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880a86d2800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880a86d2880: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
^
ffff8880a86d2900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a86d2980: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================

---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx

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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

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