KASAN: slab-out-of-bounds Read in xfrm6_tunnel_alloc_spi

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4c43049f Add linux-next specific files for 20200716
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=10e7e9d7100000
kernel config: https://syzkaller.appspot.com/x/.config?x=2c76d72659687242
dashboard link: https://syzkaller.appspot.com/bug?extid=87b2b4484df1d40e7ece
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=117f936f100000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1074fc7f100000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+87b2b4...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in __xfrm6_tunnel_alloc_spi net/ipv6/xfrm6_tunnel.c:124 [inline]
BUG: KASAN: slab-out-of-bounds in xfrm6_tunnel_alloc_spi+0x779/0x8a0 net/ipv6/xfrm6_tunnel.c:174
Read of size 4 at addr ffff88809a3fe000 by task syz-executor597/6834
CPU: 1 PID: 6834 Comm: syz-executor597 Not tainted 5.8.0-rc5-next-20200716-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+0x18f/0x20d lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
__xfrm6_tunnel_alloc_spi net/ipv6/xfrm6_tunnel.c:124 [inline]
xfrm6_tunnel_alloc_spi+0x779/0x8a0 net/ipv6/xfrm6_tunnel.c:174
ipcomp6_tunnel_create net/ipv6/ipcomp6.c:84 [inline]
ipcomp6_tunnel_attach net/ipv6/ipcomp6.c:124 [inline]
ipcomp6_init_state net/ipv6/ipcomp6.c:159 [inline]
ipcomp6_init_state+0x2af/0x700 net/ipv6/ipcomp6.c:139
__xfrm_init_state+0x9a6/0x14b0 net/xfrm/xfrm_state.c:2498
xfrm_init_state+0x1a/0x70 net/xfrm/xfrm_state.c:2525
pfkey_msg2xfrm_state net/key/af_key.c:1291 [inline]
pfkey_add+0x1a10/0x2b70 net/key/af_key.c:1508
pfkey_process+0x66d/0x7a0 net/key/af_key.c:2834
pfkey_sendmsg+0x42d/0x800 net/key/af_key.c:3673
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:671
____sys_sendmsg+0x331/0x810 net/socket.c:2362
___sys_sendmsg+0xf3/0x170 net/socket.c:2416
__sys_sendmmsg+0x195/0x480 net/socket.c:2506
__do_sys_sendmmsg net/socket.c:2535 [inline]
__se_sys_sendmmsg net/socket.c:2532 [inline]
__x64_sys_sendmmsg+0x99/0x100 net/socket.c:2532
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x440409
Code: Bad RIP value.
RSP: 002b:00007ffea3e50018 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440409
RDX: 0400000000000282 RSI: 0000000020000180 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401c10
R13: 0000000000401ca0 R14: 0000000000000000 R15: 0000000000000000
Allocated by task 6731:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
slab_post_alloc_hook mm/slab.h:535 [inline]
slab_alloc mm/slab.c:3312 [inline]
kmem_cache_alloc+0x138/0x3a0 mm/slab.c:3482
dup_fd+0x89/0xc90 fs/file.c:293
copy_files kernel/fork.c:1459 [inline]
copy_process+0x1dd0/0x6b70 kernel/fork.c:2064
_do_fork+0xe8/0xb10 kernel/fork.c:2434
__do_sys_clone+0xc8/0x110 kernel/fork.c:2551
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
entry_SYSCALL_64_after_hwframe+0x44/0xa9
The buggy address belongs to the object at ffff88809a3fe0c0
which belongs to the cache files_cache of size 832
The buggy address is located 192 bytes to the left of
832-byte region [ffff88809a3fe0c0, ffff88809a3fe400)
The buggy address belongs to the page:
page:000000007671797d refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88809a3fec00 pfn:0x9a3fe
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00027a5248 ffffea0002a3b648 ffff88821bc47600
raw: ffff88809a3fec00 ffff88809a3fe0c0 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff88809a3fdf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88809a3fdf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88809a3fe000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff88809a3fe080: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
ffff88809a3fe100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+87b2b4...@syzkaller.appspotmail.com

Tested on:

commit: 26027945 Add linux-next specific files for 20200724
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
kernel config: https://syzkaller.appspot.com/x/.config?x=e1ca07290989303a

dashboard link: https://syzkaller.appspot.com/bug?extid=87b2b4484df1d40e7ece
compiler: gcc (GCC) 10.1.0-syz 20200507

patch: https://syzkaller.appspot.com/x/patch.diff?x=13423454900000

Note: testing is done by a robot and is best-effort only.

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.