KASAN: use-after-free Read in __cfg8NUM_wpan_dev_from_attrs (2)

From: syzbot
Date: Sun Jul 05 2020 - 14:42:24 EST

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Hello,

syzbot found the following crash on:

HEAD commit: e44f65fd xen-netfront: remove redundant assignment to vari..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=120f87e5100000
kernel config: https://syzkaller.appspot.com/x/.config?x=829871134ca5e230
dashboard link: https://syzkaller.appspot.com/bug?extid=14e0e4960091ffae7cf7
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11818aa7100000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10f997d3100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+14e0e4960091ffae7cf7@xxxxxxxxxxxxxxxxxxxxxxxxx

netlink: 26 bytes leftover after parsing attributes in process `syz-executor982'.
==================================================================
BUG: KASAN: use-after-free in nla_len include/net/netlink.h:1135 [inline]
BUG: KASAN: use-after-free in nla_memcpy+0x9c/0xa0 lib/nlattr.c:724
Read of size 2 at addr ffff8880a0ca8414 by task syz-executor982/6816

CPU: 0 PID: 6816 Comm: syz-executor982 Not tainted 5.8.0-rc2-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/0x436 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
nla_len include/net/netlink.h:1135 [inline]
nla_memcpy+0x9c/0xa0 lib/nlattr.c:724
nla_get_u64 include/net/netlink.h:1606 [inline]
__cfg802154_wpan_dev_from_attrs+0x3e0/0x510 net/ieee802154/nl802154.c:55
nl802154_prepare_wpan_dev_dump.constprop.0+0xf9/0x490 net/ieee802154/nl802154.c:245
nl802154_dump_llsec_dev+0xc0/0xb10 net/ieee802154/nl802154.c:1655
genl_lock_dumpit+0x7f/0xb0 net/netlink/genetlink.c:575
netlink_dump+0x4cd/0xf60 net/netlink/af_netlink.c:2245
__netlink_dump_start+0x643/0x900 net/netlink/af_netlink.c:2353
genl_family_rcv_msg_dumpit+0x2ac/0x310 net/netlink/genetlink.c:638
genl_family_rcv_msg net/netlink/genetlink.c:733 [inline]
genl_rcv_msg+0x797/0x9e0 net/netlink/genetlink.c:753
netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2469
genl_rcv+0x24/0x40 net/netlink/genetlink.c:764
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6e8/0x810 net/socket.c:2352
___sys_sendmsg+0xf3/0x170 net/socket.c:2406
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2439
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:359
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4413c9
Code: Bad RIP value.
RSP: 002b:00007fff5b30bca8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004413c9
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00000000006cb018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000402140
R13: 00000000004021d0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6815:
save_stack+0x1b/0x40 mm/kasan/common.c:48
set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:494
__kmalloc_reserve net/core/skbuff.c:142 [inline]
__alloc_skb+0xae/0x550 net/core/skbuff.c:210
alloc_skb include/linux/skbuff.h:1083 [inline]
netlink_alloc_large_skb net/netlink/af_netlink.c:1175 [inline]
netlink_sendmsg+0x94f/0xd90 net/netlink/af_netlink.c:1893
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6e8/0x810 net/socket.c:2352
___sys_sendmsg+0xf3/0x170 net/socket.c:2406
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2439
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:359
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 6815:
save_stack+0x1b/0x40 mm/kasan/common.c:48
set_track mm/kasan/common.c:56 [inline]
kasan_set_free_info mm/kasan/common.c:316 [inline]
__kasan_slab_free+0xf5/0x140 mm/kasan/common.c:455
__cache_free mm/slab.c:3426 [inline]
kfree+0x103/0x2c0 mm/slab.c:3757
skb_free_head net/core/skbuff.c:590 [inline]
skb_release_data+0x6d9/0x910 net/core/skbuff.c:610
skb_release_all net/core/skbuff.c:664 [inline]
__kfree_skb net/core/skbuff.c:678 [inline]
consume_skb net/core/skbuff.c:837 [inline]
consume_skb+0xc2/0x160 net/core/skbuff.c:831
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x53b/0x7d0 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6e8/0x810 net/socket.c:2352
___sys_sendmsg+0xf3/0x170 net/socket.c:2406
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2439
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:359
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff8880a0ca8400
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 20 bytes inside of
512-byte region [ffff8880a0ca8400, ffff8880a0ca8600)
The buggy address belongs to the page:
page:ffffea0002832a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00029e1288 ffffea00028ef888 ffff8880aa000a80
raw: 0000000000000000 ffff8880a0ca8000 0000000100000004 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a0ca8300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880a0ca8380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a0ca8400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880a0ca8480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a0ca8500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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Next message: Waiman Long: "Re: [PATCH v3] x86/speculation/l1tf: Add KConfig for setting the L1D cache flush mode"
Previous message: Lukas Bulwahn: "Re: [PATCH] MAINTAINERS: adjust entry to renaming and conversion"
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