From: Alexey Dobriyan Additions and removal from tty_drivers list were just done as well as iterating on it for /proc/tty/drivers generation. testing: modprobe/rmmod loop of simple module which does nothing but tty_register_driver() vs cat /proc/tty/drivers loop BUG: unable to handle kernel paging request at virtual address 6b6b6b6b printing eip: c01cefa7 *pde = 00000000 Oops: 0000 [#1] PREEMPT last sysfs file: devices/pci0000:00/0000:00:1d.7/usb5/5-0:1.0/bInterfaceProtocol Modules linked in: ohci_hcd af_packet e1000 ehci_hcd uhci_hcd usbcore xfs CPU: 0 EIP: 0060:[] Not tainted VLI EFLAGS: 00010297 (2.6.21-rc4-mm1 #4) EIP is at vsnprintf+0x3a4/0x5fc eax: 6b6b6b6b ebx: f6cb50f2 ecx: 6b6b6b6b edx: fffffffe esi: c0354700 edi: f6cb6000 ebp: 6b6b6b6b esp: f31f5e68 ds: 007b es: 007b fs: 00d8 gs: 0033 ss: 0068 Process cat (pid: 31864, ti=f31f4000 task=c1998030 task.ti=f31f4000) Stack: 00000000 c0103f20 c013003a c0103f20 00000000 f6cb50da 0000000a 00000f0e f6cb50f2 00000010 00000014 ffffffff ffffffff 00000007 c0354753 f6cb50f2 f73e39dc f73e39dc 00000001 c0175416 f31f5ed8 f31f5ed4 0ee00000 f32090bc Call Trace: [] restore_nocheck+0x12/0x15 [] mark_held_locks+0x6d/0x86 [] restore_nocheck+0x12/0x15 [] seq_printf+0x2e/0x52 [] show_tty_range+0x35/0x1f3 [] seq_printf+0x2e/0x52 [] show_tty_driver+0x8a/0x1d9 [] seq_read+0x70/0x2ba [] seq_read+0x0/0x2ba [] proc_reg_read+0x63/0x9f [] vfs_read+0x7d/0xb5 [] proc_reg_read+0x0/0x9f [] sys_read+0x41/0x6a [] sysenter_past_esp+0x5f/0x99 ======================= Code: 00 8b 4d 04 e9 44 ff ff ff 8d 4d 04 89 4c 24 50 8b 6d 00 81 fd ff 0f 00 00 b8 a4 c1 35 c0 0f 46 e8 8b 54 24 2c 89 e9 89 c8 eb 06 <80> 38 00 74 07 40 4a 83 fa ff 75 f4 29 c8 89 c6 8b 44 24 28 89 EIP: [] vsnprintf+0x3a4/0x5fc SS:ESP 0068:f31f5e68 Signed-off-by: Alexey Dobriyan Cc: Alan Cox Signed-off-by: Andrew Morton --- drivers/char/tty_io.c | 5 ++++- fs/proc/proc_tty.c | 3 +++ 2 files changed, 7 insertions(+), 1 deletion(-) diff -puN drivers/char/tty_io.c~protect-tty-drivers-list-with-tty_mutex drivers/char/tty_io.c --- a/drivers/char/tty_io.c~protect-tty-drivers-list-with-tty_mutex +++ a/drivers/char/tty_io.c @@ -3771,7 +3771,9 @@ int tty_register_driver(struct tty_drive if (!driver->put_char) driver->put_char = tty_default_put_char; + mutex_lock(&tty_mutex); list_add(&driver->tty_drivers, &tty_drivers); + mutex_unlock(&tty_mutex); if ( !(driver->flags & TTY_DRIVER_DYNAMIC_DEV) ) { for(i = 0; i < driver->num; i++) @@ -3797,8 +3799,9 @@ int tty_unregister_driver(struct tty_dri unregister_chrdev_region(MKDEV(driver->major, driver->minor_start), driver->num); - + mutex_lock(&tty_mutex); list_del(&driver->tty_drivers); + mutex_unlock(&tty_mutex); /* * Free the termios and termios_locked structures because diff -puN fs/proc/proc_tty.c~protect-tty-drivers-list-with-tty_mutex fs/proc/proc_tty.c --- a/fs/proc/proc_tty.c~protect-tty-drivers-list-with-tty_mutex +++ a/fs/proc/proc_tty.c @@ -108,6 +108,8 @@ static void *t_start(struct seq_file *m, { struct list_head *p; loff_t l = *pos; + + mutex_lock(&tty_mutex); list_for_each(p, &tty_drivers) if (!l--) return list_entry(p, struct tty_driver, tty_drivers); @@ -124,6 +126,7 @@ static void *t_next(struct seq_file *m, static void t_stop(struct seq_file *m, void *v) { + mutex_unlock(&tty_mutex); } static struct seq_operations tty_drivers_op = { _