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tty_43: Check a bitset from userspace is valid before shifting it 

Passing a negative value to these legacy compat ioctls results in
left shift on a negative value which is undefined behaviour and results
in the tty (at least, possibly other things) locking up.

The argument to the ioctl should always be > 0. Return EINVAL otherwise.

While here, adjustments to code style to match current guidelines.

Found by UBSan.

Reported-by: syzbot+39cd551a05298b222756@syzkaller.appspotmail.com
This commit is contained in:
nia 2020-10-09 10:41:53 +00:00
parent ad11505eeb
commit c32467e149
1 changed files with 10 additions and 6 deletions
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16
sys/compat/common/tty_43.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: tty_43.c,v 1.37 2020/08/08 19:04:58 christos Exp $ */
/* $NetBSD: tty_43.c,v 1.38 2020/10/09 10:41:53 nia Exp $ */
/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
@ -62,7 +62,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tty_43.c,v 1.37 2020/08/08 19:04:58 christos Exp $");
__KERNEL_RCSID(0, "$NetBSD: tty_43.c,v 1.38 2020/10/09 10:41:53 nia Exp $");
#if defined(_KERNEL_OPT)
#include "opt_compat_netbsd.h"
@ -220,20 +220,24 @@ compat_43_ttioctl(struct tty *tp, u_long com, void *data, int flag,
case TIOCLBIC:
case TIOCLSET: {
struct termios term;
int flags;
int argbits, flags;
argbits = *(int *)data;
if (argbits < 0)
return EINVAL;
mutex_spin_enter(&tty_lock);
term = tp->t_termios;
flags = ttcompatgetflags(tp);
switch (com) {
case TIOCLSET:
tp->t_flags = (flags&0xffff) | (*(int *)data<<16);
tp->t_flags = (flags & 0xffff) | (argbits << 16);
break;
case TIOCLBIS:
tp->t_flags = flags | (*(int *)data<<16);
tp->t_flags = flags | (argbits << 16);
break;
case TIOCLBIC:
tp->t_flags = flags & ~(*(int *)data<<16);
tp->t_flags = flags & ~(argbits << 16);
break;
}
ttcompatsetlflags(tp, &term);