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* KASAN: use-after-free Write in tcindex_set_parms
@ 2020-03-10 22:15 syzbot
  2020-03-16 18:39 ` Cong Wang
  0 siblings, 1 reply; 2+ messages in thread
From: syzbot @ 2020-03-10 22:15 UTC (permalink / raw)
  To: davem, jhs, jiri, kuba, linux-kernel, netdev, syzkaller-bugs,


syzbot found the following crash on:

HEAD commit:    30bb5572 Merge tag 'ktest-v5.6' of git://
git tree:       upstream
console output:
kernel config:
dashboard link:
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:
C reproducer:

The bug was bisected to:

commit 599be01ee567b61f4471ee8078870847d0a11e8e
Author: Cong Wang <>
Date:   Mon Feb 3 05:14:35 2020 +0000

    net_sched: fix an OOB access in cls_tcindex

bisection log:
final crash:
console output:

IMPORTANT: if you fix the bug, please add the following tag to the commit:
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
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 for more information about syzbot.
syzbot engineers can be reached at

syzbot will keep track of this bug report. See: for how to communicate with syzbot.
For information about bisection process see:
syzbot can test patches for this bug, for details see:

^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: KASAN: use-after-free Write in tcindex_set_parms
  2020-03-10 22:15 KASAN: use-after-free Write in tcindex_set_parms syzbot
@ 2020-03-16 18:39 ` Cong Wang
  0 siblings, 0 replies; 2+ messages in thread
From: Cong Wang @ 2020-03-16 18:39 UTC (permalink / raw)
  To: syzbot
  Cc: David Miller, Jamal Hadi Salim, Jiri Pirko, Jakub Kicinski, LKML,
	Linux Kernel Network Developers, syzkaller-bugs

#syz fix: net_sched: keep alloc_hash updated after hash allocation

^ permalink raw reply	[flat|nested] 2+ messages in thread

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2020-03-10 22:15 KASAN: use-after-free Write in tcindex_set_parms syzbot
2020-03-16 18:39 ` Cong Wang

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