vt/vgacon: Check if screen resize request comes from userspace

Various console drivers are able to resize the screen via the con_resize()
hook.  This hook is also visible in userspace via the TIOCWINSZ, VT_RESIZE and
VT_RESIZEX ioctl's.  One particular utility, SVGATextMode, expects that
con_resize() of the VGA console will always return success even if the
resulting screen is not compatible with the hardware.  However, this
particular behavior of the VGA console, as reported in Kernel Bugzilla Bug
7513, can cause undefined behavior if the user starts with a console size
larger than 80x25.

To work around this problem, add an extra parameter to con_resize().  This
parameter is ignored by drivers except for vgacon.  If this parameter is
non-zero, then the resize request came from a VT_RESIZE or VT_RESIZEX ioctl
and vgacon will always return success.  If this parameter is zero, vgacon will
return -EINVAL if the requested size is not compatible with the hardware.  The
latter is the more correct behavior.

With this change, SVGATextMode should still work correctly while in-kernel and
stty resize calls can expect correct behavior from vgacon.

Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index edb7002a32161e1868ca510d27d74116605e9cfd..0d56f8fc105c9314fb9b9e73b539d8acbb7ddfe1 100644 (file)
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -750,13 +750,15 @@ int vc_allocate(unsigned int currcons)    /* return 0 on success */
        return 0;
 }
 
-static inline int resize_screen(struct vc_data *vc, int width, int height)
+static inline int resize_screen(struct vc_data *vc, int width, int height,
+                               int user)
 {
        /* Resizes the resolution of the display adapater */
        int err = 0;
 
        if (vc->vc_mode != KD_GRAPHICS && vc->vc_sw->con_resize)
-               err = vc->vc_sw->con_resize(vc, width, height);
+               err = vc->vc_sw->con_resize(vc, width, height, user);
+
        return err;
 }
 
@@ -772,7 +774,7 @@ int vc_resize(struct vc_data *vc, unsigned int cols, unsigned int lines)
        unsigned long old_origin, new_origin, new_scr_end, rlth, rrem, err = 0;
        unsigned int old_cols, old_rows, old_row_size, old_screen_size;
        unsigned int new_cols, new_rows, new_row_size, new_screen_size;
-       unsigned int end;
+       unsigned int end, user;
        unsigned short *newscreen;
 
        WARN_CONSOLE_UNLOCKED();
@@ -780,6 +782,9 @@ int vc_resize(struct vc_data *vc, unsigned int cols, unsigned int lines)
        if (!vc)
                return -ENXIO;
 
+       user = vc->vc_resize_user;
+       vc->vc_resize_user = 0;
+
        if (cols > VC_RESIZE_MAXCOL || lines > VC_RESIZE_MAXROW)
                return -EINVAL;
 
@@ -800,7 +805,7 @@ int vc_resize(struct vc_data *vc, unsigned int cols, unsigned int lines)
        old_row_size = vc->vc_size_row;
        old_screen_size = vc->vc_screenbuf_size;
 
-       err = resize_screen(vc, new_cols, new_rows);
+       err = resize_screen(vc, new_cols, new_rows, user);
        if (err) {
                kfree(newscreen);
                return err;

diff --git a/drivers/char/vt_ioctl.c b/drivers/char/vt_ioctl.c
index 7a61a2a9aafe3879dc8a0e443fd7d1379e7e493e..f69a8258095cf6de5129f0ba9190f060ae5e5628 100644 (file)
--- a/drivers/char/vt_ioctl.c
+++ b/drivers/char/vt_ioctl.c
@@ -847,14 +847,24 @@ int vt_ioctl(struct tty_struct *tty, struct file * file,
        case VT_RESIZE:
        {
                struct vt_sizes __user *vtsizes = up;
+               struct vc_data *vc;
+
                ushort ll,cc;
                if (!perm)
                        return -EPERM;
                if (get_user(ll, &vtsizes->v_rows) ||
                    get_user(cc, &vtsizes->v_cols))
                        return -EFAULT;
-               for (i = 0; i < MAX_NR_CONSOLES; i++)
-                       vc_lock_resize(vc_cons[i].d, cc, ll);
+
+               for (i = 0; i < MAX_NR_CONSOLES; i++) {
+                       vc = vc_cons[i].d;
+
+                       if (vc) {
+                               vc->vc_resize_user = 1;
+                               vc_lock_resize(vc_cons[i].d, cc, ll);
+                       }
+               }
+
                return 0;
        }
 
@@ -900,6 +910,7 @@ int vt_ioctl(struct tty_struct *tty, struct file * file,
                                vc_cons[i].d->vc_scan_lines = vlin;
                        if (clin)
                                vc_cons[i].d->vc_font.height = clin;
+                       vc_cons[i].d->vc_resize_user = 1;
                        vc_resize(vc_cons[i].d, cc, ll);
                        release_console_sem();
                }

diff --git a/drivers/usb/misc/sisusbvga/sisusb_con.c b/drivers/usb/misc/sisusbvga/sisusb_con.c
index 43722e5a49d13e93bf4671af5daea1f02765f67e..b624320df903da090c8380f59d06593d8c648302 100644 (file)
--- a/drivers/usb/misc/sisusbvga/sisusb_con.c
+++ b/drivers/usb/misc/sisusbvga/sisusb_con.c
@@ -1042,7 +1042,8 @@ sisusbcon_set_origin(struct vc_data *c)
 
 /* Interface routine */
 static int
-sisusbcon_resize(struct vc_data *c, unsigned int newcols, unsigned int newrows)
+sisusbcon_resize(struct vc_data *c, unsigned int newcols, unsigned int newrows,
+                unsigned int user)
 {
        struct sisusb_usb_data *sisusb;
        int fh;

diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index 6d0dcde66eb4a1a3646503efc89c1f0b677832dd..97a0224a0cf06e5225a27611c191e23159011d0b 100644 (file)
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -2168,7 +2168,7 @@ static __inline__ void updatescrollmode(struct display *p,
 }
 
 static int fbcon_resize(struct vc_data *vc, unsigned int width, 
-                       unsigned int height)
+                       unsigned int height, unsigned int user)
 {
        struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
        struct fbcon_ops *ops = info->fbcon_par;

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index d18b73aafa0d16af70fdf41886ee3e2fbcf00b09..e9afb7ebd566144a53f68552ad6f7f1b5b34bb9f 100644 (file)
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -1278,13 +1278,14 @@ static int vgacon_font_get(struct vc_data *c, struct console_font *font)
 #endif
 
 static int vgacon_resize(struct vc_data *c, unsigned int width,
-                               unsigned int height)
+                        unsigned int height, unsigned int user)
 {
        if (width % 2 || width > ORIG_VIDEO_COLS ||
            height > (ORIG_VIDEO_LINES * vga_default_font_height)/
            c->vc_font.height)
-               /* let svgatextmode tinker with video timings */
-               return 0;
+               /* let svgatextmode tinker with video timings and
+                  return success */
+               return (user) ? 0 : -EINVAL;
 
        if (CON_IS_VISIBLE(c) && !vga_is_gfx) /* who knows */
                vgacon_doresize(c, width, height);

diff --git a/include/linux/console.h b/include/linux/console.h
index 56a7bcda49cb202cdbcc0093ee8fd8437edbd5d2..0a4542ddb73dab19ceb9477e22241dc3bc0fe33e 100644 (file)
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -45,7 +45,8 @@ struct consw {
        int     (*con_font_get)(struct vc_data *, struct console_font *);
        int     (*con_font_default)(struct vc_data *, struct console_font *, char *);
        int     (*con_font_copy)(struct vc_data *, int);
-       int     (*con_resize)(struct vc_data *, unsigned int, unsigned int);
+       int     (*con_resize)(struct vc_data *, unsigned int, unsigned int,
+                              unsigned int);
        int     (*con_set_palette)(struct vc_data *, unsigned char *);
        int     (*con_scrolldelta)(struct vc_data *, int);
        int     (*con_set_origin)(struct vc_data *);

diff --git a/include/linux/console_struct.h b/include/linux/console_struct.h
index dc77fed7b28566c585ccc2193f14dfdea8227421..d71f7c0f931b34b63bfacde2b06d19ffc5001616 100644 (file)
--- a/include/linux/console_struct.h
+++ b/include/linux/console_struct.h
@@ -100,6 +100,7 @@ struct vc_data {
        unsigned char   vc_G1_charset;
        unsigned char   vc_saved_G0;
        unsigned char   vc_saved_G1;
+       unsigned int    vc_resize_user;         /* resize request from user */
        unsigned int    vc_bell_pitch;          /* Console bell pitch */
        unsigned int    vc_bell_duration;       /* Console bell duration */
        struct vc_data **vc_display_fg;         /* [!] Ptr to var holding fg console for this display */