Subject: KASAN: invalid-free in tcf_exts_destroy

From: syzbot <[email-masked]>
Date: Sun, 08 Mar 2020 12:35:12 -0700

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=10cd2ae3e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4527d1e2fb19fd5c
dashboard link: https://syzkaller.appspot.com/bug?extid=dcc34d54d68ef7d2d53d
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
userspace arch: i386
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1561b01de00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15aad2f9e00000

The bug was bisected to:

commit 599be01ee567b61f4471ee8078870847d0a11e8e
Author: Cong Wang <[email-masked]>
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=10a275fde00000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=12a275fde00000
console output: https://syzkaller.appspot.com/x/log.txt?x=14a275fde00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]
Fixes: 599be01ee567 ("net_sched: fix an OOB access in cls_tcindex")

IPVS: ftp: loaded support on port[0] = 21
==================================================================
BUG: KASAN: double-free or invalid-free in tcf_exts_destroy+0x62/0xc0 net/sched/cls_api.c:3002

CPU: 1 PID: 9507 Comm: syz-executor467 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_invalid_free+0x61/0xa0 mm/kasan/report.c:468
 __kasan_slab_free+0x129/0x140 mm/kasan/common.c:455
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x109/0x2b0 mm/slab.c:3757
 tcf_exts_destroy+0x62/0xc0 net/sched/cls_api.c:3002
 tcf_exts_change+0xf4/0x150 net/sched/cls_api.c:3059
 tcindex_set_parms+0xed8/0x1a00 net/sched/cls_tcindex.c:456
 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_32_irqs_on arch/x86/entry/common.c:337 [inline]
 do_fast_syscall_32+0x270/0xe8f arch/x86/entry/common.c:408
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

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]
 __class_register+0x46/0x450 drivers/base/class.c:160
 spi_transport_init+0xf0/0x132 drivers/scsi/scsi_transport_spi.c:1609
 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 0:
(stack is not available)

The buggy address belongs to the object at ffff8880a12d5000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 152 bytes inside of
 1024-byte region [ffff8880a12d5000, ffff8880a12d5400)
The buggy address belongs to the page:
page:ffffea000284b540 refcount:1 mapcount:0 mapping:ffff8880aa000c40 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000285c288 ffffea000284b588 ffff8880aa000c40
raw: 0000000000000000 ffff8880a12d5000 0000000100000002 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a12d4f80: 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a12d5000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880a12d5080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                            ^
 ffff8880a12d5100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880a12d5180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

---
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