BUG: unable to handle kernel paging request in n_tty_open

[Hao Sun]

Hi

When using Healer(https://github.com/SunHao-0/healer/tree/dev) to fuzz
the Linux kernel, I found the following bug report, but I'm not sure
about this.
Sorry, I do not have a reproducing program for this bug.
I hope that the stack trace information in the crash log can help you
locate the problem.

Here is the details:
commit:   52e44129fba5cfc4e351fdb5e45849afc74d9a53
version:   linux 5.12
git tree:    upstream

================================================================
RAX: ffffffffffffffda RBX: 000000000059c080 RCX: 000000000041a204
RDX: 0000000000000002 RSI: 00007f3a14cc5820 RDI: 00000000ffffff9c
RBP: 00007f3a14cc5820 R08: 0000000000000000 R09: 000000000000000e
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000002
R13: 00007ffd67854d6f R14: 00007ffd67854f10 R15: 00007f3a14cc5dc0
BUG: unable to handle page fault for address: ffff9d8941065050
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 1810067 P4D 1810067 PUD 1915067 PMD 4902067 PTE 0
Oops: 0002 [#1] SMP
CPU: 0 PID: 6311 Comm: syz-executor Not tainted 5.12.0-rc6+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:n_tty_open+0xbb/0x2d0 drivers/tty/n_tty.c:1925
Code: 48 c7 c7 80 79 80 90 e8 53 a2 c4 fc 4d 8d 7c 24 50 4c 8b 30 8b
02 89 45 cc 4d 85 ed 0f 85 90 01 00 00 4c 89 ff e8 55 a2 c4 fc <4c> 89
30 4d 85 f6 0f 85 89 01 00 00 48 8b 45 b8 49 89 44 24 50 49
RSP: 0018:ffff9589410635a8 EFLAGS: 00010286
RAX: ffff9d8941065050 RBX: ffff935284a28a98 RCX: ffff9d8941065050
RDX: ffffa58941065050 RSI: 0000000000000008 RDI: ffff958941065050
RBP: ffff9589410635f8 R08: ffffdbfdc000000f R09: ffff9352fffd3000
R10: 0000000088d5e5c3 R11: ffff958941067fff R12: ffff958941065000
R13: 0000000000000000 R14: 0000000000000000 R15: ffff958941065050
FS:  00007f3a14cc6700(0000) GS:ffff9352ffa00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff9d8941065050 CR3: 000000002e898003 CR4: 0000000000770ef0
PKRU: 55555554
Call Trace:
 tty_ldisc_close drivers/tty/tty_ldisc.c:487 [inline]
 tty_ldisc_setup+0x11d/0x600 drivers/tty/tty_ldisc.c:784
 tty_init_dev+0x51d/0xaf0 drivers/tty/tty_io.c:3154
 tty_open+0xf9f/0x1fd0 drivers/tty/tty_io.c:3588
 chrdev_open+0xc14/0xd80 fs/stat.c:93
 build_open_how fs/open.c:996 [inline]
 do_dentry_open+0xf36/0x17b0 fs/open.c:1163
 d_backing_inode ./include/linux/dcache.h:552 [inline]
 vfs_open fs/open.c:940 [inline]
 vfs_open+0xaf/0xe0 fs/open.c:956
 fsnotify_name ./include/linux/fsnotify.h:33 [inline]
 fsnotify_move ./include/linux/fsnotify.h:149 [inline]
 path_openat+0x4d57/0x5e10 fs/namei.c:4580
 do_filp_open+0x2b8/0x710 fs/namei.c:3495
 do_sys_openat2+0x222/0x770 fs/open.c:1207
 __se_sys_openat+0x24c/0x2b0
 build_open_how fs/open.c:990 [inline]
 do_sys_open fs/open.c:1202 [inline]
 __do_sys_openat fs/open.c:1219 [inline]
 __se_sys_openat fs/open.c:1214 [inline]
 __x64_sys_openat+0x56/0x70 fs/open.c:1214
 do_syscall_32_irqs_on arch/x86/entry/common.c:76 [inline]
 do_syscall_64+0xa2/0x120 arch/x86/entry/common.c:94
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x41a204
Code: 24 20 eb 8f 66 90 44 89 54 24 0c e8 86 f9 ff ff 44 8b 54 24 0c
44 89 e2 48 89 ee 41 89 c0 bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d
00 f0 ff ff 77 32 44 89 c7 89 44 24 0c e8 b8 f9 ff ff 8b 44
RSP: 002b:00007f3a14cc5780 EFLAGS: 00000293 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 000000000059c080 RCX: 000000000041a204
RDX: 0000000000000002 RSI: 00007f3a14cc5820 RDI: 00000000ffffff9c
RBP: 00007f3a14cc5820 R08: 0000000000000000 R09: 000000000000000e
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000002
R13: 00007ffd67854d6f R14: 00007ffd67854f10 R15: 00007f3a14cc5dc0
Modules linked in:
Dumping ftrace buffer:
   (ftrace buffer empty)
CR2: ffff9d8941065050
---[ end trace 1057db73ffbbbc86 ]---
RIP: 0010:n_tty_open+0xbb/0x2d0 drivers/tty/n_tty.c:1925
Code: 48 c7 c7 80 79 80 90 e8 53 a2 c4 fc 4d 8d 7c 24 50 4c 8b 30 8b
02 89 45 cc 4d 85 ed 0f 85 90 01 00 00 4c 89 ff e8 55 a2 c4 fc <4c> 89
30 4d 85 f6 0f 85 89 01 00 00 48 8b 45 b8 49 89 44 24 50 49
RSP: 0018:ffff9589410635a8 EFLAGS: 00010286
RAX: ffff9d8941065050 RBX: ffff935284a28a98 RCX: ffff9d8941065050
RDX: ffffa58941065050 RSI: 0000000000000008 RDI: ffff958941065050
RBP: ffff9589410635f8 R08: ffffdbfdc000000f R09: ffff9352fffd3000
R10: 0000000088d5e5c3 R11: ffff958941067fff R12: ffff958941065000
R13: 0000000000000000 R14: 0000000000000000 R15: ffff958941065050
FS:  00007f3a14cc6700(0000) GS:ffff9352ffa00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff9d8941065050 CR3: 000000002e898003 CR4: 0000000000770ef0
PKRU: 55555554

Attachment: config
Description: Binary data