Re: [syzbot] [net?] general protection fault in generic_hwtstamp_ioctl_lower (2)

[Jakub Kicinski <kuba@kernel.org>]

On Tue, 04 Feb 2025 07:22:16 -0800 syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    69e858e0b8b2 Merge tag 'uml-for-linus-6.14-rc1' of git://g..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13324b24580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=98d83cc1742b7377
> dashboard link: https://syzkaller.appspot.com/bug?extid=86a8ab09a0f655f1ff19
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17324b24580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=161595f8580000

Hi Kory!

Looks like syzbot wasn't able to bisect and didn't CC you.
Please take a look, looks like struct kernel_hwtstamp_config
gets into the ioctl paths.

> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/3d07b0558b0e/disk-69e858e0.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/e5e2250eb3b1/vmlinux-69e858e0.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/3e676d17effc/bzImage-69e858e0.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+86a8ab09a0f655f1ff19@syzkaller.appspotmail.com
> 
> netdevsim netdevsim0 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
> netdevsim netdevsim0 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
> netdevsim netdevsim0 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0
> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
> CPU: 0 UID: 0 PID: 5827 Comm: syz-executor976 Not tainted 6.13.0-syzkaller-09760-g69e858e0b8b2 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
> RIP: 0010:generic_hwtstamp_ioctl_lower+0x125/0x420 net/core/dev_ioctl.c:456
> Code: fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 b7 02 00 00 48 ba 00 00 00 00 00 fc ff df 4d 8b 75 10 49 8d 7e 10 48 89 f8 48 c1 e8 03 <0f> b6 0c 10 49 8d 46 27 48 89 c6 83 e0 07 48 c1 ee 03 0f b6 14 16
> RSP: 0018:ffffc90003e4f250 EFLAGS: 00010202
> RAX: 0000000000000002 RBX: ffff88807c788000 RCX: 0000000000000000
> RDX: dffffc0000000000 RSI: ffffffff893547b8 RDI: 0000000000000010
> RBP: ffffc90003e4f338 R08: 0000000000000007 R09: 0000000000000003
> R10: ffffc90003e4f2ab R11: 0000000000000001 R12: 1ffff920007c9e4e
> R13: ffffc90003e4f410 R14: 0000000000000000 R15: 1ffff920007c9e9b
> FS:  0000555562e35380(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000180 CR3: 0000000078b1a000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  generic_hwtstamp_get_lower net/core/dev_ioctl.c:480 [inline]
>  generic_hwtstamp_get_lower+0xe8/0x130 net/core/dev_ioctl.c:468
>  dev_get_hwtstamp_phylib+0x181/0x610 net/core/dev_ioctl.c:291
>  tsconfig_prepare_data+0x15f/0x650 net/ethtool/tsconfig.c:51
>  ethnl_default_doit+0x31a/0xbd0 net/ethtool/netlink.c:493
>  genl_family_rcv_msg_doit+0x202/0x2f0 net/netlink/genetlink.c:1115
>  genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
>  genl_rcv_msg+0x565/0x800 net/netlink/genetlink.c:1210
>  netlink_rcv_skb+0x165/0x410 net/netlink/af_netlink.c:2543
>  genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
>  netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline]
>  netlink_unicast+0x53c/0x7f0 net/netlink/af_netlink.c:1348
>  netlink_sendmsg+0x8b8/0xd70 net/netlink/af_netlink.c:1892
>  sock_sendmsg_nosec net/socket.c:713 [inline]
>  __sock_sendmsg net/socket.c:728 [inline]
>  ____sys_sendmsg+0x9ae/0xb40 net/socket.c:2568
>  ___sys_sendmsg+0x135/0x1e0 net/socket.c:2622
>  __sys_sendmsg+0x16e/0x220 net/socket.c:2654
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f098155c919
> Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffca30ea5f8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 00007f09815aa4ad RCX: 00007f098155c919
> RDX: 0000000000000000 RSI: 0000000020000280 RDI: 0000000000000003
> RBP: 00007f09815aa47d R08: 0000000000000000 R09: 0000555500000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f09815aa3e5
> R13: 0000000000000001 R14: 00007ffca30ea640 R15: 0000000000000003
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:generic_hwtstamp_ioctl_lower+0x125/0x420 net/core/dev_ioctl.c:456
> Code: fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 b7 02 00 00 48 ba 00 00 00 00 00 fc ff df 4d 8b 75 10 49 8d 7e 10 48 89 f8 48 c1 e8 03 <0f> b6 0c 10 49 8d 46 27 48 89 c6 83 e0 07 48 c1 ee 03 0f b6 14 16
> RSP: 0018:ffffc90003e4f250 EFLAGS: 00010202
> RAX: 0000000000000002 RBX: ffff88807c788000 RCX: 0000000000000000
> RDX: dffffc0000000000 RSI: ffffffff893547b8 RDI: 0000000000000010
> RBP: ffffc90003e4f338 R08: 0000000000000007 R09: 0000000000000003
> R10: ffffc90003e4f2ab R11: 0000000000000001 R12: 1ffff920007c9e4e
> R13: ffffc90003e4f410 R14: 0000000000000000 R15: 1ffff920007c9e9b
> FS:  0000555562e35380(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000180 CR3: 0000000078b1a000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess), 3 bytes skipped:
>    0:	48 c1 ea 03          	shr    $0x3,%rdx
>    4:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
>    8:	0f 85 b7 02 00 00    	jne    0x2c5
>    e:	48 ba 00 00 00 00 00 	movabs $0xdffffc0000000000,%rdx
>   15:	fc ff df
>   18:	4d 8b 75 10          	mov    0x10(%r13),%r14
>   1c:	49 8d 7e 10          	lea    0x10(%r14),%rdi
>   20:	48 89 f8             	mov    %rdi,%rax
>   23:	48 c1 e8 03          	shr    $0x3,%rax
> * 27:	0f b6 0c 10          	movzbl (%rax,%rdx,1),%ecx <-- trapping instruction
>   2b:	49 8d 46 27          	lea    0x27(%r14),%rax
>   2f:	48 89 c6             	mov    %rax,%rsi
>   32:	83 e0 07             	and    $0x7,%eax
>   35:	48 c1 ee 03          	shr    $0x3,%rsi
>   39:	0f b6 14 16          	movzbl (%rsi,%rdx,1),%edx
> 
> 
> ---
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