Subject: general protection fault in ethnl_parse_header

From: syzbot <[email-masked]>
Date: Thu, 19 Mar 2020 06:37:12 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    2de9780f net: core: dev.c: fix a documentation warning
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=131b4023e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c2e311dba9a02ba9
dashboard link: https://syzkaller.appspot.com/bug?extid=258a9089477493cea67b
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15a3a7c3e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1661ab55e00000

The bug was bisected to:

commit 2363d73a2f3e92787f336721c40918ba2eb0c74c
Author: Michal Kubecek <[email-masked]>
Date:   Sun Mar 15 17:17:53 2020 +0000

    ethtool: reject unrecognized request flags

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1778561de00000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=14f8561de00000
console output: https://syzkaller.appspot.com/x/log.txt?x=10f8561de00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]
Fixes: 2363d73a2f3e ("ethtool: reject unrecognized request flags")

general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
CPU: 1 PID: 9619 Comm: syz-executor891 Not tainted 5.6.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:ethnl_parse_header+0x522/0x840 include/linux/string.h:381
Code: ea 03 80 3c 02 00 0f 85 1d 03 00 00 4d 89 7d 08 e8 d3 70 2d fb 49 8d 7d 10 48 ba 00 00 00 00 00 fc ff df 48 89 f8 48 c1 e8 03 <0f> b6 0c 10 49 8d 45 13 48 89 c6 48 c1 ee 03 0f b6 14 16 48 89 fe
RSP: 0018:ffffc90001f8f4d8 EFLAGS: 00010202
RAX: 0000000000000002 RBX: ffff8880a2593048 RCX: ffffffff8644a170
RDX: dffffc0000000000 RSI: ffffffff8644a4ed RDI: 0000000000000010
RBP: ffff8880a4436980 R08: ffff88809e586500 R09: ffffc90001f8f510
R10: fffff520003f1ea5 R11: ffffc90001f8f52f R12: 1ffff920003f1e9e
R13: 0000000000000000 R14: ffffffff8a343040 R15: ffff8880a259304c
FS:  000000000251d880(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000043eaf0 CR3: 00000000a23d2000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 ethnl_default_parse+0x1c1/0x300 net/ethtool/netlink.c:264
 ethnl_default_start+0x1ed/0x4d0 net/ethtool/netlink.c:492
 __netlink_dump_start+0x58a/0x910 net/netlink/af_netlink.c:2343
 genl_family_rcv_msg_dumpit net/netlink/genetlink.c:630 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:715 [inline]
 genl_rcv_msg+0xa32/0xdf0 net/netlink/genetlink.c:735
 netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2469
 genl_rcv+0x24/0x40 net/netlink/genetlink.c:746
 netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
 netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329
 netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:672
 ____sys_sendmsg+0x6b9/0x7d0 net/socket.c:2343
 ___sys_sendmsg+0x100/0x170 net/socket.c:2397
 __sys_sendmsg+0xec/0x1b0 net/socket.c:2430
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x444319
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 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 1b d8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffc9883dca8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002e0 RCX: 0000000000444319
RDX: 0000000000000000 RSI: 0000000020006440 RDI: 0000000000000003
RBP: 00000000006ce018 R08: 0000000000000008 R09: 00000000004002e0
R10: 000000000000000c R11: 0000000000000246 R12: 0000000000401fc0
R13: 0000000000402050 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace e7c6f01e7d795112 ]---
RIP: 0010:ethnl_parse_header+0x522/0x840 include/linux/string.h:381
Code: ea 03 80 3c 02 00 0f 85 1d 03 00 00 4d 89 7d 08 e8 d3 70 2d fb 49 8d 7d 10 48 ba 00 00 00 00 00 fc ff df 48 89 f8 48 c1 e8 03 <0f> b6 0c 10 49 8d 45 13 48 89 c6 48 c1 ee 03 0f b6 14 16 48 89 fe
RSP: 0018:ffffc90001f8f4d8 EFLAGS: 00010202
RAX: 0000000000000002 RBX: ffff8880a2593048 RCX: ffffffff8644a170
RDX: dffffc0000000000 RSI: ffffffff8644a4ed RDI: 0000000000000010
RBP: ffff8880a4436980 R08: ffff88809e586500 R09: ffffc90001f8f510
R10: fffff520003f1ea5 R11: ffffc90001f8f52f R12: 1ffff920003f1e9e
R13: 0000000000000000 R14: ffffffff8a343040 R15: ffff8880a259304c
FS:  000000000251d880(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000043eaf0 CR3: 00000000a23d2000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

---
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