| 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
| ||
|
Message-ID: <ZiD1dih_LQik_zWS@example.org>
Date: Thu, 18 Apr 2024 12:27:02 +0200
From: Alexey Gladkov <legion@...nel.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jiri Slaby <jirislaby@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
kbd@...ts.linux.dev, linux-api@...r.kernel.org,
linux-fbdev@...r.kernel.org, linux-serial@...r.kernel.org,
Helge Deller <deller@....de>
Subject: Re: [PATCH v5 2/3] VT: Add KDFONTINFO ioctl
On Thu, Apr 18, 2024 at 08:18:33AM +0200, Greg Kroah-Hartman wrote:
> On Wed, Apr 17, 2024 at 07:37:36PM +0200, Alexey Gladkov wrote:
> > Each driver has its own restrictions on font size. There is currently no
> > way to understand what the requirements are. The new ioctl allows
> > userspace to get the minimum and maximum font size values.
>
> Is there any userspace code that uses this yet that we can point to
> here?
Yes. I have a code that uses this. It waits for this ioctl to appear in
the kernel.
https://git.kernel.org/pub/scm/linux/kernel/git/legion/kbd.git/commit/?h=kdfontinfo-v1&id=e2ad0117ca8e46cedd8668934db7b04e9054d5d7
> I know tty ioctls are woefully undocumented, but could there be some
> documentation here?
Yes, this is a big problem for this interface. The ioctl_console(2)
describes PIO_FONT/PIO_FONTX, which is no longer supported, but does not
describe KDFONTOP at all, which is exactly used by userspace.
My TODO has a task to fix this.
But I would suggest creating documentation in the kernel because life
shows that man-page is far behind what is implemented.
> >
> > Acked-by: Helge Deller <deller@....de>
> > Signed-off-by: Alexey Gladkov <legion@...nel.org>
> > ---
> > drivers/tty/vt/vt.c | 24 ++++++++++++++++++++++++
> > drivers/tty/vt/vt_ioctl.c | 13 +++++++++++++
> > include/linux/console.h | 3 +++
> > include/linux/vt_kern.h | 1 +
> > include/uapi/linux/kd.h | 14 ++++++++++++++
> > 5 files changed, 55 insertions(+)
> >
> > diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
> > index 9b5b98dfc8b4..e8db0e9ea674 100644
> > --- a/drivers/tty/vt/vt.c
> > +++ b/drivers/tty/vt/vt.c
> > @@ -4851,6 +4851,30 @@ int con_font_op(struct vc_data *vc, struct console_font_op *op)
> > return -ENOSYS;
> > }
> >
> > +int con_font_info(struct vc_data *vc, struct console_font_info *info)
> > +{
> > + int rc;
> > +
> > + info->min_height = 0;
> > + info->max_height = max_font_height;
> > +
> > + info->min_width = 0;
> > + info->max_width = max_font_width;
> > +
> > + info->flags = KD_FONT_INFO_FLAG_LOW_SIZE | KD_FONT_INFO_FLAG_HIGH_SIZE;
> > +
> > + console_lock();
> > + if (vc->vc_mode != KD_TEXT)
> > + rc = -EINVAL;
> > + else if (vc->vc_sw->con_font_info)
> > + rc = vc->vc_sw->con_font_info(vc, info);
> > + else
> > + rc = -ENOSYS;
> > + console_unlock();
> > +
> > + return rc;
> > +}
> > +
> > /*
> > * Interface exported to selection and vcs.
> > */
> > diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
> > index 4b91072f3a4e..9a2f8081f650 100644
> > --- a/drivers/tty/vt/vt_ioctl.c
> > +++ b/drivers/tty/vt/vt_ioctl.c
> > @@ -479,6 +479,19 @@ static int vt_k_ioctl(struct tty_struct *tty, unsigned int cmd,
> > break;
> > }
> >
> > + case KDFONTINFO: {
> > + struct console_font_info fnt_info;
> > +
> > + memset(&fnt_info, 0, sizeof(fnt_info));
> > +
> > + ret = con_font_info(vc, &fnt_info);
>
> Shouldn't con_font_info() memset it first? No need to do it in the
> caller.
>
> > + if (ret)
> > + return ret;
> > + if (copy_to_user(up, &fnt_info, sizeof(fnt_info)))
> > + return -EFAULT;
> > + break;
> > + }
> > +
> > default:
> > return -ENOIOCTLCMD;
> > }
> > diff --git a/include/linux/console.h b/include/linux/console.h
> > index 31a8f5b85f5d..4b798322aa01 100644
> > --- a/include/linux/console.h
> > +++ b/include/linux/console.h
> > @@ -21,6 +21,7 @@
> > #include <linux/vesa.h>
> >
> > struct vc_data;
> > +struct console_font_info;
> > struct console_font_op;
> > struct console_font;
> > struct module;
> > @@ -102,6 +103,8 @@ struct consw {
> > bool (*con_switch)(struct vc_data *vc);
> > bool (*con_blank)(struct vc_data *vc, enum vesa_blank_mode blank,
> > bool mode_switch);
> > + int (*con_font_info)(struct vc_data *vc,
> > + struct console_font_info *info);
>
> To make the names more obvious, how about:
> con_font_info_get()?
>
> > int (*con_font_set)(struct vc_data *vc,
> > const struct console_font *font,
> > unsigned int vpitch, unsigned int flags);
> > diff --git a/include/linux/vt_kern.h b/include/linux/vt_kern.h
> > index d008c3d0a9bb..383b3a4f6113 100644
> > --- a/include/linux/vt_kern.h
> > +++ b/include/linux/vt_kern.h
> > @@ -33,6 +33,7 @@ void do_blank_screen(int entering_gfx);
> > void do_unblank_screen(int leaving_gfx);
> > void poke_blanked_console(void);
> > int con_font_op(struct vc_data *vc, struct console_font_op *op);
> > +int con_font_info(struct vc_data *vc, struct console_font_info *info);
> > int con_set_cmap(unsigned char __user *cmap);
> > int con_get_cmap(unsigned char __user *cmap);
> > void scrollback(struct vc_data *vc);
> > diff --git a/include/uapi/linux/kd.h b/include/uapi/linux/kd.h
> > index 8ddb2219a84b..68b715ad4d5c 100644
> > --- a/include/uapi/linux/kd.h
> > +++ b/include/uapi/linux/kd.h
> > @@ -185,6 +185,20 @@ struct console_font {
> >
> > #define KD_FONT_FLAG_DONT_RECALC 1 /* Don't recalculate hw charcell size [compat] */
> >
> > +/* font information */
> > +
> > +#define KD_FONT_INFO_FLAG_LOW_SIZE _BITUL(0) /* 256 */
> > +#define KD_FONT_INFO_FLAG_HIGH_SIZE _BITUL(1) /* 512 */
>
> I don't understand why bit 0 and bit 1 have those comments after them.
> That's confusing (i.e. bit 0 is NOT 256...)
>
> > +
> > +struct console_font_info {
> > + __u32 flags; /* KD_FONT_INFO_FLAG_* */
>
> Why are there flags if you are only setting these 2 values? What are
> the flags for?
>
> If this is going to be a "multiplexed" type of structure, then make it a
> union? Or maybe we are totally over thinking this whole thing.
>
> All you want is the min/max font size of the console, right? So perhaps
> the whole structure is just:
>
> > + __u32 min_width, min_height; /* minimal font size */
> > + __u32 max_width, max_height; /* maximum font size */
>
> Those 4 variables? Why have anything else here at all? For any new
> thing you wish to discover, have it be a new ioctl?
>
> > + __u32 reserved[5]; /* This field is reserved for future use. Must be 0. */
>
> I understand the "must be 0" but this is a read-only structure, so
> saying "it will be set to 0" might be better?" Or something like that?
>
> > +};
> > +
> > +#define KDFONTINFO _IOR(KD_IOCTL_BASE, 0x73, struct console_font_info)
>
> As mentioned above how about KDFONTINFOGET?
>
> thanks,
>
> greg k-h
>
--
Rgrds, legion
Powered by blists - more mailing lists