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SubjectKASAN: slab-out-of-bounds Read in xfrm_policy_lookup_bytype
From
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=17648ab3400000
kernel config: https://syzkaller.appspot.com/x/.config?x=d9655b05acfc97ff
dashboard link: https://syzkaller.appspot.com/bug?extid=485623f77eab9345799d
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+485623f77eab9345799d@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in __xfrm_policy_eval_candidates
net/xfrm/xfrm_policy.c:2019 [inline]
BUG: KASAN: slab-out-of-bounds in xfrm_policy_eval_candidates
net/xfrm/xfrm_policy.c:2053 [inline]
BUG: KASAN: slab-out-of-bounds in xfrm_policy_lookup_bytype+0xe5d/0xe80
net/xfrm/xfrm_policy.c:2116
Read of size 4 at addr ffff8881c178e0b4 by task syz-executor5/21772

CPU: 1 PID: 21772 Comm: syz-executor5 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
raw_sendmsg+0xfe2/0x2ac0 net/ipv4/raw.c:647
inet_sendmsg+0x1a1/0x690 net/ipv4/af_inet.c:798
sock_sendmsg_nosec net/socket.c:621 [inline]
sock_sendmsg+0xd5/0x120 net/socket.c:631
__sys_sendto+0x3d7/0x670 net/socket.c:1788
__do_sys_sendto net/socket.c:1800 [inline]
__se_sys_sendto net/socket.c:1796 [inline]
__x64_sys_sendto+0xe1/0x1a0 net/socket.c:1796
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:00007f1c03de9c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 0000000000457669
RDX: 0000000000000000 RSI: 0000000020000100 RDI: 0000000000000003
RBP: 000000000072bf00 R08: 0000000020000040 R09: 0000000000000010
R10: 000000000404c0c0 R11: 0000000000000246 R12: 00007f1c03dea6d4
R13: 00000000004c452d R14: 00000000004d7590 R15: 00000000ffffffff

Allocated by task 12834:
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
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
kmem_cache_alloc+0x12e/0x730 mm/slab.c:3554
getname_flags+0xd0/0x590 fs/namei.c:140
user_path_at_empty+0x2d/0x50 fs/namei.c:2608
user_path_at include/linux/namei.h:57 [inline]
vfs_statx+0x129/0x210 fs/stat.c:185
vfs_stat include/linux/fs.h:3165 [inline]
__do_sys_newstat+0x8f/0x110 fs/stat.c:339
__se_sys_newstat fs/stat.c:335 [inline]
__x64_sys_newstat+0x54/0x80 fs/stat.c:335
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 12834:
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]
kmem_cache_free+0x83/0x290 mm/slab.c:3760
putname+0xf2/0x130 fs/namei.c:261
filename_lookup+0x39a/0x520 fs/namei.c:2357
user_path_at_empty+0x40/0x50 fs/namei.c:2608
user_path_at include/linux/namei.h:57 [inline]
vfs_statx+0x129/0x210 fs/stat.c:185
vfs_stat include/linux/fs.h:3165 [inline]
__do_sys_newstat+0x8f/0x110 fs/stat.c:339
__se_sys_newstat fs/stat.c:335 [inline]
__x64_sys_newstat+0x54/0x80 fs/stat.c:335
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 ffff8881c178e3c0
which belongs to the cache names_cache of size 4096
The buggy address is located 780 bytes to the left of
4096-byte region [ffff8881c178e3c0, ffff8881c178f3c0)
The buggy address belongs to the page:
page:ffffea000705e380 count:1 mapcount:0 mapping:ffff8881da980e00 index:0x0
compound_mapcount: 0
flags: 0x2fffc0000010200(slab|head)
raw: 02fffc0000010200 ffffea000714a388 ffffea0006312b08 ffff8881da980e00
raw: 0000000000000000 ffff8881c178e3c0 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881c178df80: fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881c178e000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8881c178e080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff8881c178e100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881c178e180: fc fc fc fc fc fc fc fc 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@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
syzbot.

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