[syzbot] general protection fault in hci_uart_tty_ioctl

[syzbot <syzbot+c19afa60d78984711078@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    7ebfc85e2cd7 Merge tag 'net-6.0-rc1' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14aad4f3080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=924833c12349a8c0
dashboard link: https://syzkaller.appspot.com/bug?extid=c19afa60d78984711078
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15669ae3080000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=156d9b4b080000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c19afa60d78984711078@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 PID: 3641 Comm: syz-executor395 Not tainted 5.19.0-syzkaller-13930-g7ebfc85e2cd7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
RIP: 0010:hci_uart_tty_ioctl+0x23f/0xc20 drivers/bluetooth/hci_ldisc.c:771
Code: df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 cb 08 00 00 48 8b 9b b8 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 68 08 00 00 44 8b 23 e9 14 ff
RSP: 0018:ffffc90003b8fd10 EFLAGS: 00010256
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff86978565 RDI: ffff88807902a0b8
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 000000000008c07c R12: ffff88801cb1a000
R13: 0000000000000000 R14: ffffffffffffffea R15: ffff888020e03b20
FS:  00007fef078ad700(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff911ec960 CR3: 0000000071d89000 CR4: 0000000000350ee0
Call Trace:
 <TASK>
 tty_ioctl+0x1045/0x15d0 drivers/tty/tty_io.c:2787
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fef0791cee9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 41 15 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:00007fef078ad318 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fef079a53f8 RCX: 00007fef0791cee9
RDX: 0000000000000000 RSI: 00000000800455c9 RDI: 0000000000000003
RBP: 00007fef079a53f0 R08: 00007fef078ad700 R09: 0000000000000000
R10: 00007fef078ad700 R11: 0000000000000246 R12: 6d74702f7665642f
R13: 00007fff911b316f R14: 00007fef078ad400 R15: 0000000000022000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:hci_uart_tty_ioctl+0x23f/0xc20 drivers/bluetooth/hci_ldisc.c:771
Code: df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 cb 08 00 00 48 8b 9b b8 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 68 08 00 00 44 8b 23 e9 14 ff
RSP: 0018:ffffc90003b8fd10 EFLAGS: 00010256
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff86978565 RDI: ffff88807902a0b8
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 000000000008c07c R12: ffff88801cb1a000
R13: 0000000000000000 R14: ffffffffffffffea R15: ffff888020e03b20
FS:  00007fef078ad700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fef079641c0 CR3: 0000000071d89000 CR4: 0000000000350ef0
----------------
Code disassembly (best guess):
   0:	df 48 89             	fisttps -0x77(%rax)
   3:	fa                   	cli
   4:	48 c1 ea 03          	shr    $0x3,%rdx
   8:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
   c:	0f 85 cb 08 00 00    	jne    0x8dd
  12:	48 8b 9b b8 00 00 00 	mov    0xb8(%rbx),%rbx
  19:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  20:	fc ff df
  23:	48 89 da             	mov    %rbx,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	0f b6 04 02          	movzbl (%rdx,%rax,1),%eax <-- trapping instruction
  2e:	84 c0                	test   %al,%al
  30:	74 08                	je     0x3a
  32:	3c 03                	cmp    $0x3,%al
  34:	0f 8e 68 08 00 00    	jle    0x8a2
  3a:	44 8b 23             	mov    (%rbx),%r12d
  3d:	e9                   	.byte 0xe9
  3e:	14 ff                	adc    $0xff,%al


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