KASAN: use-after-free Read in _decode_session6

Status: fixed on 2019/11/07 18:45
Subsystems: net
[Documentation on labels]
Reported-by: syzbot+e8c1d30881266e47eb33@syzkaller.appspotmail.com
Fix commit: e7c87bd6cc4e bpf: in __bpf_redirect_no_mac pull mac only if present
First crash: 2883d, last: 2815d
Fix bisection: fixed by (bisect log) :
commit e7c87bd6cc4ec7b0ac1ed0a88a58f8206c577488
Author: Willem de Bruijn <willemb@google.com>
Date: Wed Jan 16 01:19:22 2019 +0000

  bpf: in __bpf_redirect_no_mac pull mac only if present

  
▶ ▼ Discussions (3)
Title Replies (including bot) Last reply
KASAN: use-after-free Read in _decode_session6 1 (3) 2019/11/07 14:31
Reminder: 26 open syzbot bugs in "net/xfrm" subsystem 1 (1) 2019/07/24 01:42
Reminder: 27 open syzbot bugs in "net/xfrm" subsystem 1 (1) 2019/06/25 05:51
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.19 KASAN: slab-out-of-bounds Read in _decode_session6 19 23 1681d 2335d 0/1 auto-closed as invalid on 2022/04/20 21:31
linux-4.19 KASAN: use-after-free Read in _decode_session6 (2) 19 1 1533d 1533d 0/1 auto-obsoleted due to no activity on 2022/09/15 14:44
linux-4.14 KASAN: use-after-free Read in _decode_session6 19 2 2257d 2266d 0/1 auto-closed as invalid on 2020/09/21 07:45
linux-4.19 KASAN: use-after-free Read in _decode_session6 19 2 2226d 2258d 0/1 auto-closed as invalid on 2020/10/22 17:34
android-414 KASAN: use-after-free Read in _decode_session6 19 1 2876d 2876d 0/1 auto-closed as invalid on 2019/03/12 14:41

Sample crash report:
audit: type=1400 audit(1536202560.246:9): avc:  denied  { prog_run } for  pid=4752 comm="syz-executor726" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=bpf permissive=1
==================================================================
BUG: KASAN: use-after-free in _decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161
Read of size 1 at addr ffff8801bb87e97f by task syz-executor726/4752

CPU: 0 PID: 4752 Comm: syz-executor726 Not tainted 4.19.0-rc2+ #2
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+0x1c9/0x2b4 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x30d mm/kasan/report.c:412
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
 _decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161
 __xfrm_decode_session+0x71/0x140 net/xfrm/xfrm_policy.c:2299
 xfrm_decode_session include/net/xfrm.h:1232 [inline]
 vti6_tnl_xmit+0x3fc/0x1bb1 net/ipv6/ip6_vti.c:542
 __netdev_start_xmit include/linux/netdevice.h:4287 [inline]
 netdev_start_xmit include/linux/netdevice.h:4296 [inline]
 xmit_one net/core/dev.c:3216 [inline]
 dev_hard_start_xmit+0x272/0xc10 net/core/dev.c:3232
 __dev_queue_xmit+0x2ab2/0x3870 net/core/dev.c:3802
 dev_queue_xmit+0x17/0x20 net/core/dev.c:3835
 __bpf_tx_skb net/core/filter.c:2012 [inline]
 __bpf_redirect_common net/core/filter.c:2050 [inline]
 __bpf_redirect+0x5b7/0xae0 net/core/filter.c:2057
 ____bpf_clone_redirect net/core/filter.c:2090 [inline]
 bpf_clone_redirect+0x2f6/0x490 net/core/filter.c:2062
 bpf_prog_c39d1ba309a769f7+0xd1e/0x1000

Allocated by task 4752:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
 __do_kmalloc_node mm/slab.c:3682 [inline]
 __kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3696
 __kmalloc_reserve.isra.41+0x3a/0xe0 net/core/skbuff.c:137
 pskb_expand_head+0x230/0x10e0 net/core/skbuff.c:1463
 skb_ensure_writable+0x3dd/0x640 net/core/skbuff.c:5129
 __bpf_try_make_writable net/core/filter.c:1633 [inline]
 bpf_try_make_writable net/core/filter.c:1639 [inline]
 bpf_try_make_head_writable net/core/filter.c:1647 [inline]
 ____bpf_clone_redirect net/core/filter.c:2084 [inline]
 bpf_clone_redirect+0x14a/0x490 net/core/filter.c:2062
 bpf_prog_c39d1ba309a769f7+0xd1e/0x1000

Freed by task 4752:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kfree+0xd9/0x210 mm/slab.c:3813
 skb_free_head+0x99/0xc0 net/core/skbuff.c:550
 skb_release_data+0x6a4/0x880 net/core/skbuff.c:570
 skb_release_all+0x4a/0x60 net/core/skbuff.c:627
 __kfree_skb net/core/skbuff.c:641 [inline]
 kfree_skb+0x19d/0x4e0 net/core/skbuff.c:659
 vti6_tnl_xmit+0x387/0x1bb1 net/ipv6/ip6_vti.c:561
 __netdev_start_xmit include/linux/netdevice.h:4287 [inline]
 netdev_start_xmit include/linux/netdevice.h:4296 [inline]
 xmit_one net/core/dev.c:3216 [inline]
 dev_hard_start_xmit+0x272/0xc10 net/core/dev.c:3232
 __dev_queue_xmit+0x2ab2/0x3870 net/core/dev.c:3802
 dev_queue_xmit+0x17/0x20 net/core/dev.c:3835
 __bpf_tx_skb net/core/filter.c:2012 [inline]
 __bpf_redirect_common net/core/filter.c:2050 [inline]
 __bpf_redirect+0x5b7/0xae0 net/core/filter.c:2057
 ____bpf_clone_redirect net/core/filter.c:2090 [inline]
 bpf_clone_redirect+0x2f6/0x490 net/core/filter.c:2062
 bpf_prog_c39d1ba309a769f7+0xd1e/0x1000

The buggy address belongs to the object at ffff8801bb87e780
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 511 bytes inside of
 512-byte region [ffff8801bb87e780, ffff8801bb87e980)
The buggy address belongs to the page:
page:ffffea0006ee1f80 count:1 mapcount:0 mapping:ffff8801dac00940 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0006eefd48 ffffea00073f5f08 ffff8801dac00940
raw: 0000000000000000 ffff8801bb87e000 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bb87e800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801bb87e880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801bb87e900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff8801bb87e980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801bb87ea00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/09/06 02:58 upstream b36fdc6853a3 873745f2 .config console log report syz C ci-upstream-kasan-gce-selinux-root
2018/09/06 06:15 bpf-next 69495d2a5295 873745f2 .config console log report syz C ci-upstream-bpf-next-kasan-gce
2018/11/13 14:23 bpf-next 407be8d03e20 5f5f6d14 .config console log report ci-upstream-bpf-next-kasan-gce
2018/10/29 14:42 bpf-next 44adbac8f721 7df9db2e .config console log report ci-upstream-bpf-next-kasan-gce
* Struck through repros no longer work on HEAD.