Subject: KASAN: use-after-free Read in nl8NUM_dump_wpan_phy (2)

From: syzbot <[email-masked]>
Date: Fri, 26 Jun 2020 10:08:16 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    b835a71e usbnet: smsc95xx: Fix use-after-free after removal
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=106721ad100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=dcc6334acae363d4
dashboard link: https://syzkaller.appspot.com/bug?extid=4c8afc85aa32ddb020dc
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13c25419100000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1768f009100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]

netlink: 'syz-executor532': attribute type 3 has an invalid length.
==================================================================
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 ffff8880a46aec14 by task syz-executor532/6937

CPU: 1 PID: 6937 Comm: syz-executor532 Not tainted 5.8.0-rc1-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]
 nl802154_dump_wpan_phy_parse net/ieee802154/nl802154.c:559 [inline]
 nl802154_dump_wpan_phy+0x59b/0x9c0 net/ieee802154/nl802154.c:593
 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: 0033:0x441409
Code: Bad RIP value.
RSP: 002b:00007ffda49cc2b8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000441409
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00000000006cc018 R08: 0000000120080522 R09: 0000000120080522
R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000402220
R13: 00000000004022b0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6962:
 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 6962:
 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 ffff8880a46aec00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 20 bytes inside of
 512-byte region [ffff8880a46aec00, ffff8880a46aee00)
The buggy address belongs to the page:
page:ffffea000291ab80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00028dee88 ffffea0002548e08 ffff8880aa000a80
raw: 0000000000000000 ffff8880a46ae000 0000000100000004 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a46aeb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a46aeb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a46aec00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff8880a46aec80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a46aed00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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