linux-kernel - Re: [PATCH 07/33] tty: vt: use

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <97ec2636-915a-498c-903b-d66957420d21@csgroup.eu>
Date: Thu, 31 Jul 2025 16:35:56 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: "Jiri Slaby (SUSE)" <jirislaby@...nel.org>, gregkh@...uxfoundation.org,
 Christian Zigotzky <chzigotzky@...osoft.de>
Cc: linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
 Nicolas Pitre <nico@...xnic.net>,
 "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH 07/33] tty: vt: use _IO() to define ioctl numbers

Hi Jiri,

Le 11/06/2025 à 12:02, Jiri Slaby (SUSE) a écrit :
> _IO*() is the proper way of defining ioctl numbers. All these vt numbers
> were synthetically built up the same way the _IO() macro does.
> 
> So instead of implicit hex numbers, use _IO() properly.
> 
> To not change the pre-existing numbers, use only _IO() (and not _IOR()
> or _IOW()). The latter would change the numbers indeed.

On powerpc your assumption is wrong, because _IOC_NONE is not 0:

$ git grep _IOC_NONE arch/powerpc/
arch/powerpc/include/uapi/asm/ioctl.h:#define _IOC_NONE 1U

Therefore the value changes even with _IO(), leading to failure of Xorg 
as reported by Christian.

Christophe

> 
> Objdump of vt_ioctl.o reveals no difference with this patch.
> 
> Again, VT_GETCONSIZECSRPOS already uses _IOR(), so everything is paved
> for this patch.
> 
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
> Cc: Nicolas Pitre <nico@...xnic.net>
> ---
>   include/uapi/linux/vt.h | 34 +++++++++++++++++-----------------
>   1 file changed, 17 insertions(+), 17 deletions(-)
> 
> diff --git a/include/uapi/linux/vt.h b/include/uapi/linux/vt.h
> index 714483d68c69..b60fcdfb2746 100644
> --- a/include/uapi/linux/vt.h
> +++ b/include/uapi/linux/vt.h
> @@ -14,9 +14,9 @@
>   		/* Note: the ioctl VT_GETSTATE does not work for
>   		   consoles 16 and higher (since it returns a short) */
>   
> -/* 0x56 is 'V', to avoid collision with termios and kd */
> +/* 'V' to avoid collision with termios and kd */
>   
> -#define VT_OPENQRY	0x5600	/* find available vt */
> +#define VT_OPENQRY		_IO('V', 0x00)	/* find available vt */
>   
>   struct vt_mode {
>   	__u8 mode;		/* vt mode */
> @@ -25,8 +25,8 @@ struct vt_mode {
>   	__s16 acqsig;		/* signal to raise on acquisition */
>   	__s16 frsig;		/* unused (set to 0) */
>   };
> -#define VT_GETMODE	0x5601	/* get mode of active vt */
> -#define VT_SETMODE	0x5602	/* set mode of active vt */
> +#define VT_GETMODE		_IO('V', 0x01)	/* get mode of active vt */
> +#define VT_SETMODE		_IO('V', 0x02)	/* set mode of active vt */
>   #define		VT_AUTO		0x00	/* auto vt switching */
>   #define		VT_PROCESS	0x01	/* process controls switching */
>   #define		VT_ACKACQ	0x02	/* acknowledge switch */
> @@ -36,21 +36,21 @@ struct vt_stat {
>   	__u16 v_signal;	/* signal to send */
>   	__u16 v_state;		/* vt bitmask */
>   };
> -#define VT_GETSTATE	0x5603	/* get global vt state info */
> -#define VT_SENDSIG	0x5604	/* signal to send to bitmask of vts */
> +#define VT_GETSTATE		_IO('V', 0x03)	/* get global vt state info */
> +#define VT_SENDSIG		_IO('V', 0x04)	/* signal to send to bitmask of vts */
>   
> -#define VT_RELDISP	0x5605	/* release display */
> +#define VT_RELDISP		_IO('V', 0x05)	/* release display */
>   
> -#define VT_ACTIVATE	0x5606	/* make vt active */
> -#define VT_WAITACTIVE	0x5607	/* wait for vt active */
> -#define VT_DISALLOCATE	0x5608  /* free memory associated to vt */
> +#define VT_ACTIVATE		_IO('V', 0x06)	/* make vt active */
> +#define VT_WAITACTIVE		_IO('V', 0x07)	/* wait for vt active */
> +#define VT_DISALLOCATE		_IO('V', 0x08)  /* free memory associated to vt */
>   
>   struct vt_sizes {
>   	__u16 v_rows;		/* number of rows */
>   	__u16 v_cols;		/* number of columns */
>   	__u16 v_scrollsize;	/* number of lines of scrollback */
>   };
> -#define VT_RESIZE	0x5609	/* set kernel's idea of screensize */
> +#define VT_RESIZE		_IO('V', 0x09)	/* set kernel's idea of screensize */
>   
>   struct vt_consize {
>   	__u16 v_rows;	/* number of rows */
> @@ -60,10 +60,10 @@ struct vt_consize {
>   	__u16 v_vcol;	/* number of pixel columns on screen */
>   	__u16 v_ccol;	/* number of pixel columns per character */
>   };
> -#define VT_RESIZEX      0x560A  /* set kernel's idea of screensize + more */
> -#define VT_LOCKSWITCH   0x560B  /* disallow vt switching */
> -#define VT_UNLOCKSWITCH 0x560C  /* allow vt switching */
> -#define VT_GETHIFONTMASK 0x560D  /* return hi font mask */
> +#define VT_RESIZEX		_IO('V', 0x0A)  /* set kernel's idea of screensize + more */
> +#define VT_LOCKSWITCH		_IO('V', 0x0B)  /* disallow vt switching */
> +#define VT_UNLOCKSWITCH		_IO('V', 0x0C)  /* allow vt switching */
> +#define VT_GETHIFONTMASK	_IO('V', 0x0D)  /* return hi font mask */
>   
>   struct vt_event {
>   	__u32 event;
> @@ -77,14 +77,14 @@ struct vt_event {
>   	__u32 pad[4];		/* Padding for expansion */
>   };
>   
> -#define VT_WAITEVENT	0x560E	/* Wait for an event */
> +#define VT_WAITEVENT		_IO('V', 0x0E)	/* Wait for an event */
>   
>   struct vt_setactivate {
>   	__u32 console;
>   	struct vt_mode mode;
>   };
>   
> -#define VT_SETACTIVATE	0x560F	/* Activate and set the mode of a console */
> +#define VT_SETACTIVATE		_IO('V', 0x0F)	/* Activate and set the mode of a console */
>   
>   /* get console size and cursor position */
>   struct vt_consizecsrpos {