KASAN: use-after-free Read in xfrm_policy_lookup_bytype

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 33f18c96afdf net: ethernet: don't set phylib state CHANGEL..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=160b54cd400000
kernel config: https://syzkaller.appspot.com/x/.config?x=d9655b05acfc97ff
dashboard link: https://syzkaller.appspot.com/bug?extid=87da0517ca1d154f0610
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+87da05...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in __xfrm_policy_eval_candidates
net/xfrm/xfrm_policy.c:2019 [inline]
BUG: KASAN: use-after-free in xfrm_policy_eval_candidates
net/xfrm/xfrm_policy.c:2053 [inline]
BUG: KASAN: use-after-free in xfrm_policy_lookup_bytype+0xe5d/0xe80
net/xfrm/xfrm_policy.c:2116
Read of size 4 at addr ffff8881d82352b4 by task syz-executor2/15691

CPU: 1 PID: 15691 Comm: syz-executor2 Not tainted 4.20.0-rc6+ #353
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+0x244/0x39d lib/dump_stack.c:113
print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
__xfrm_policy_eval_candidates net/xfrm/xfrm_policy.c:2019 [inline]
xfrm_policy_eval_candidates net/xfrm/xfrm_policy.c:2053 [inline]
xfrm_policy_lookup_bytype+0xe5d/0xe80 net/xfrm/xfrm_policy.c:2116
xfrm_policy_lookup+0x7e/0x80 net/xfrm/xfrm_policy.c:2148
xfrm_bundle_lookup net/xfrm/xfrm_policy.c:2942 [inline]
xfrm_lookup_with_ifid+0x972/0x2b80 net/xfrm/xfrm_policy.c:3083
xfrm_lookup net/xfrm/xfrm_policy.c:3175 [inline]
xfrm_lookup_route+0x3c/0x1f0 net/xfrm/xfrm_policy.c:3186
ip_route_output_flow+0xb1/0xc0 net/ipv4/route.c:2582
ip_route_connect include/net/route.h:309 [inline]
__ip4_datagram_connect+0x70e/0x1330 net/ipv4/datagram.c:51
ip4_datagram_connect+0x2f/0x50 net/ipv4/datagram.c:92
inet_dgram_connect+0x154/0x2e0 net/ipv4/af_inet.c:571
make_send_sock net/netfilter/ipvs/ip_vs_sync.c:1509 [inline]
start_sync_thread+0xf0c/0x2d20 net/netfilter/ipvs/ip_vs_sync.c:1877
do_ip_vs_set_ctl+0x10cb/0x1d70 net/netfilter/ipvs/ip_vs_ctl.c:2360
nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
nf_setsockopt+0x7d/0xd0 net/netfilter/nf_sockopt.c:115
ip_setsockopt+0xd8/0xf0 net/ipv4/ip_sockglue.c:1260
udp_setsockopt+0x62/0xa0 net/ipv4/udp.c:2611
sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:2986
__sys_setsockopt+0x1ba/0x3c0 net/socket.c:1902
__do_sys_setsockopt net/socket.c:1913 [inline]
__se_sys_setsockopt net/socket.c:1910 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:1910
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457669
Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fe3ddccec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000457669
RDX: 000000000000048b RSI: 0000000000000000 RDI: 0000000000000005
RBP: 000000000072bf00 R08: 0000000000000018 R09: 0000000000000000
R10: 0000000020000000 R11: 0000000000000246 R12: 00007fe3ddccf6d4
R13: 00000000004ca9b0 R14: 00000000004d7968 R15: 00000000ffffffff

Allocated by task 5933:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
kmalloc include/linux/slab.h:546 [inline]
syslog_print kernel/printk/printk.c:1301 [inline]
do_syslog+0xb9b/0x1690 kernel/printk/printk.c:1469
kmsg_read+0x8f/0xc0 fs/proc/kmsg.c:40
proc_reg_read+0x2a3/0x3d0 fs/proc/inode.c:231
__vfs_read+0x117/0x9b0 fs/read_write.c:416
vfs_read+0x17f/0x3c0 fs/read_write.c:452
ksys_read+0x101/0x260 fs/read_write.c:578
__do_sys_read fs/read_write.c:588 [inline]
__se_sys_read fs/read_write.c:586 [inline]
__x64_sys_read+0x73/0xb0 fs/read_write.c:586
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 5933:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xcf/0x230 mm/slab.c:3817
syslog_print kernel/printk/printk.c:1352 [inline]
do_syslog+0x147b/0x1690 kernel/printk/printk.c:1469
kmsg_read+0x8f/0xc0 fs/proc/kmsg.c:40
proc_reg_read+0x2a3/0x3d0 fs/proc/inode.c:231
__vfs_read+0x117/0x9b0 fs/read_write.c:416
vfs_read+0x17f/0x3c0 fs/read_write.c:452
ksys_read+0x101/0x260 fs/read_write.c:578
__do_sys_read fs/read_write.c:588 [inline]
__se_sys_read fs/read_write.c:586 [inline]
__x64_sys_read+0x73/0xb0 fs/read_write.c:586
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8881d8235200
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 180 bytes inside of
1024-byte region [ffff8881d8235200, ffff8881d8235600)
The buggy address belongs to the page:
page:ffffea0007608d00 count:1 mapcount:0 mapping:ffff8881da800ac0 index:0x0
compound_mapcount: 0
flags: 0x2fffc0000010200(slab|head)
raw: 02fffc0000010200 ffffea000734f608 ffffea0007021a88 ffff8881da800ac0
raw: 0000000000000000 ffff8881d8234000 0000000100000007 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881d8235180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881d8235200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8881d8235280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881d8235300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881d8235380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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[Florian Westphal]

syzbot <syzbot+87da05...@syzkaller.appspotmail.com> wrote:
> HEAD commit: 33f18c96afdf net: ethernet: don't set phylib state CHANGEL..
> git tree: net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=160b54cd400000
> kernel config: https://syzkaller.appspot.com/x/.config?x=d9655b05acfc97ff
> dashboard link: https://syzkaller.appspot.com/bug?extid=87da0517ca1d154f0610

Possibly resolved by xfrm policy fixup series whose topmost commit is

#syz fix: xfrm: policy: fix infinite loop when merging src-nodes