[syzbot] [net?] general protection fault in phy_start_cable_test_tdr

[syzbot <syzbot+5cf270e2069645b6bd2c@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    f9db28bb09f4 Merge branch 'net-redundant-judgments'
git tree:       net-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1656cc7b980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=df2f0ed7e30a639d
dashboard link: https://syzkaller.appspot.com/bug?extid=5cf270e2069645b6bd2c
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1582047b980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=100af825980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/585e02f7fe7b/disk-f9db28bb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b9faf5d24900/vmlinux-f9db28bb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f9df5868ea4f/bzImage-f9db28bb.xz

The issue was bisected to:

commit 3688ff3077d3f334cee1d4b61d8bfb6a9508c2d2
Author: Maxime Chevallier <maxime.chevallier@bootlin.com>
Date:   Wed Aug 21 15:10:05 2024 +0000

    net: ethtool: cable-test: Target the command to the requested PHY

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10163b05980000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=12163b05980000
console output: https://syzkaller.appspot.com/x/log.txt?x=14163b05980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5cf270e2069645b6bd2c@syzkaller.appspotmail.com
Fixes: 3688ff3077d3 ("net: ethtool: cable-test: Target the command to the requested PHY")

Oops: general protection fault, probably for non-canonical address 0xdffffc00000000f8: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x00000000000007c0-0x00000000000007c7]
CPU: 0 UID: 0 PID: 5234 Comm: syz-executor293 Not tainted 6.11.0-rc4-syzkaller-00565-gf9db28bb09f4 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
RIP: 0010:phy_start_cable_test_tdr+0x3a/0x5c0 drivers/net/phy/phy.c:885
Code: ec 38 48 89 54 24 18 49 89 f6 48 89 fb 49 bd 00 00 00 00 00 fc ff df e8 e4 24 2b fb 48 8d bb c0 07 00 00 48 89 f8 48 c1 e8 03 <42> 80 3c 28 00 74 05 e8 9a 66 92 fb 48 8b 83 c0 07 00 00 48 89 44
RSP: 0018:ffffc90003c7f230 EFLAGS: 00010202
RAX: 00000000000000f8 RBX: 0000000000000000 RCX: ffff888029b23c00
RDX: 0000000000000000 RSI: ffffc90003c7f740 RDI: 00000000000007c0
RBP: ffffc90003c7f470 R08: ffffffff89cb116d R09: 1ffff1100452bc15
R10: dffffc0000000000 R11: ffffffff86686630 R12: ffffc90003c7f3f0
R13: dffffc0000000000 R14: ffffc90003c7f740 R15: 0000000000000000
FS:  000055555a907380(0000) GS:ffff8880b9200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055fce9c1f000 CR3: 000000001a7d2000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ethnl_act_cable_test_tdr+0x607/0x10d0 net/ethtool/cabletest.c:350
 genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
 genl_rcv_msg+0xb14/0xec0 net/netlink/genetlink.c:1210
 netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
 netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1357
 netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x221/0x270 net/socket.c:745
 ____sys_sendmsg+0x525/0x7d0 net/socket.c:2597
 ___sys_sendmsg net/socket.c:2651 [inline]
 __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2680
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3311b2ef49
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 01 1a 00 00 90 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe6e4b3118 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f3311b2ef49
RDX: 0000000000000000 RSI: 0000000020000240 RDI: 0000000000000003
RBP: 00000000000f4240 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe6e4b3170
R13: 00007f3311b7c406 R14: 0000000000000003 R15: 00007ffe6e4b3150
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:phy_start_cable_test_tdr+0x3a/0x5c0 drivers/net/phy/phy.c:885
Code: ec 38 48 89 54 24 18 49 89 f6 48 89 fb 49 bd 00 00 00 00 00 fc ff df e8 e4 24 2b fb 48 8d bb c0 07 00 00 48 89 f8 48 c1 e8 03 <42> 80 3c 28 00 74 05 e8 9a 66 92 fb 48 8b 83 c0 07 00 00 48 89 44
RSP: 0018:ffffc90003c7f230 EFLAGS: 00010202
RAX: 00000000000000f8 RBX: 0000000000000000 RCX: ffff888029b23c00
RDX: 0000000000000000 RSI: ffffc90003c7f740 RDI: 00000000000007c0
RBP: ffffc90003c7f470 R08: ffffffff89cb116d R09: 1ffff1100452bc15
R10: dffffc0000000000 R11: ffffffff86686630 R12: ffffc90003c7f3f0
R13: dffffc0000000000 R14: ffffc90003c7f740 R15: 0000000000000000
FS:  000055555a907380(0000) GS:ffff8880b9300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3311b15a00 CR3: 000000001a7d2000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	ec                   	in     (%dx),%al
   1:	38 48 89             	cmp    %cl,-0x77(%rax)
   4:	54                   	push   %rsp
   5:	24 18                	and    $0x18,%al
   7:	49 89 f6             	mov    %rsi,%r14
   a:	48 89 fb             	mov    %rdi,%rbx
   d:	49 bd 00 00 00 00 00 	movabs $0xdffffc0000000000,%r13
  14:	fc ff df
  17:	e8 e4 24 2b fb       	call   0xfb2b2500
  1c:	48 8d bb c0 07 00 00 	lea    0x7c0(%rbx),%rdi
  23:	48 89 f8             	mov    %rdi,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 80 3c 28 00       	cmpb   $0x0,(%rax,%r13,1) <-- trapping instruction
  2f:	74 05                	je     0x36
  31:	e8 9a 66 92 fb       	call   0xfb9266d0
  36:	48 8b 83 c0 07 00 00 	mov    0x7c0(%rbx),%rax
  3d:	48                   	rex.W
  3e:	89                   	.byte 0x89
  3f:	44                   	rex.R


---
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