KASAN: use-after-free Read in rawv6_sendmsg

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 09eb2ba5 ANDROID: x86_64_cuttlefish_defconfig: Enable lz4 ..
git tree: android-4.9
console output: https://syzkaller.appspot.com/x/log.txt?x=156e17ba400000
kernel config: https://syzkaller.appspot.com/x/.config?x=59246eb7b3f7dd72
dashboard link: https://syzkaller.appspot.com/bug?extid=718aabcd4cb757851227
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1664ca1e400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+718aab...@syzkaller.appspotmail.com

IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
hrtimer: interrupt took 35785 ns
==================================================================
BUG: KASAN: use-after-free in rawv6_send_hdrinc net/ipv6/raw.c:683 [inline]
BUG: KASAN: use-after-free in rawv6_sendmsg+0x2691/0x2820 net/ipv6/raw.c:916
Read of size 8 at addr ffff8801ba755658 by task syz-executor0/8867

CPU: 0 PID: 8867 Comm: syz-executor0 Not tainted 4.9.124-g09eb2ba #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
ffff8801c8e5f6e0 ffffffff81eb95e9 ffffea0006e9d500 ffff8801ba755658
0000000000000000 ffff8801ba755658 ffff8801ba755658 ffff8801c8e5f718
ffffffff8156c35e ffff8801ba755658 0000000000000008 0000000000000000
Call Trace:
[<ffffffff81eb95e9>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffffff81eb95e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
[<ffffffff8156c35e>] print_address_description+0x6c/0x234
mm/kasan/report.c:256
[<ffffffff8156c768>] kasan_report_error mm/kasan/report.c:355 [inline]
[<ffffffff8156c768>] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412
[<ffffffff8153faf4>] __asan_report_load8_noabort+0x14/0x20
mm/kasan/report.c:433
[<ffffffff835da8c1>] rawv6_send_hdrinc net/ipv6/raw.c:683 [inline]
[<ffffffff835da8c1>] rawv6_sendmsg+0x2691/0x2820 net/ipv6/raw.c:916
[<ffffffff83431af3>] inet_sendmsg+0x203/0x4d0 net/ipv4/af_inet.c:770
[<ffffffff8301e0ac>] sock_sendmsg_nosec net/socket.c:648 [inline]
[<ffffffff8301e0ac>] sock_sendmsg+0xcc/0x110 net/socket.c:658
[<ffffffff8301e313>] sock_write_iter+0x223/0x3b0 net/socket.c:856
[<ffffffff81573440>] new_sync_write fs/read_write.c:496 [inline]
[<ffffffff81573440>] __vfs_write+0x3e0/0x580 fs/read_write.c:509
[<ffffffff81577237>] vfs_write+0x187/0x530 fs/read_write.c:557
[<ffffffff8157b069>] SYSC_write fs/read_write.c:604 [inline]
[<ffffffff8157b069>] SyS_write+0xd9/0x1c0 fs/read_write.c:596
[<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
[<ffffffff83a019d3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Allocated by task 8867:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
save_stack+0x43/0xd0 mm/kasan/kasan.c:505
set_track mm/kasan/kasan.c:517 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:609
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:547
slab_post_alloc_hook mm/slab.h:417 [inline]
slab_alloc_node mm/slub.c:2715 [inline]
slab_alloc mm/slub.c:2723 [inline]
kmem_cache_alloc+0xbe/0x290 mm/slub.c:2728
dst_alloc+0xb5/0x1a0 net/core/dst.c:210
__ip6_dst_alloc+0x31/0x130 net/ipv6/route.c:334
ip6_rt_cache_alloc.isra.49+0xe0/0x440 net/ipv6/route.c:956
ip6_pol_route+0x126d/0x1d30 net/ipv6/route.c:1109
ip6_pol_route_output+0x4c/0x60 net/ipv6/route.c:1193
fib6_rule_action+0x23f/0x6b0 net/ipv6/fib6_rules.c:89
fib_rules_lookup+0x2aa/0x8b0 net/core/fib_rules.c:265
fib6_rule_lookup+0xe8/0x1a0 net/ipv6/fib6_rules.c:43
ip6_route_output_flags+0x24b/0x2b0 net/ipv6/route.c:1221
ip6_dst_lookup_tail+0x3df/0x16c0 net/ipv6/ip6_output.c:991
ip6_dst_lookup_flow+0xaa/0x210 net/ipv6/ip6_output.c:1092
rawv6_sendmsg+0x9b5/0x2820 net/ipv6/raw.c:900
inet_sendmsg+0x203/0x4d0 net/ipv4/af_inet.c:770
sock_sendmsg_nosec net/socket.c:648 [inline]
sock_sendmsg+0xcc/0x110 net/socket.c:658
sock_write_iter+0x223/0x3b0 net/socket.c:856
new_sync_write fs/read_write.c:496 [inline]
__vfs_write+0x3e0/0x580 fs/read_write.c:509
vfs_write+0x187/0x530 fs/read_write.c:557
SYSC_write fs/read_write.c:604 [inline]
SyS_write+0xd9/0x1c0 fs/read_write.c:596
do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Freed by task 6877:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
save_stack+0x43/0xd0 mm/kasan/kasan.c:505
set_track mm/kasan/kasan.c:517 [inline]
kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:582
slab_free_hook mm/slub.c:1355 [inline]
slab_free_freelist_hook mm/slub.c:1377 [inline]
slab_free mm/slub.c:2958 [inline]
kmem_cache_free+0xbe/0x310 mm/slub.c:2980
dst_destroy+0x200/0x360 net/core/dst.c:270
dst_destroy_rcu+0x15/0x40 net/core/dst.c:295
__rcu_reclaim kernel/rcu/rcu.h:118 [inline]
rcu_do_batch kernel/rcu/tree.c:2789 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
__rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
__do_softirq+0x210/0x940 kernel/softirq.c:288

The buggy address belongs to the object at ffff8801ba755500
which belongs to the cache ip6_dst_cache of size 384
The buggy address is located 344 bytes inside of
384-byte region [ffff8801ba755500, ffff8801ba755680)
The buggy address belongs to the page:
page:ffffea0006e9d500 count:1 mapcount:0 mapping: (null)
index:0xffff8801ba754a80 compound_mapcount: 0
flags: 0x8000000000004080(slab|head)
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801ba755500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801ba755580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801ba755600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801ba755680: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
ffff8801ba755700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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