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SubjectRe: [linux-fbdev] Re: Video driver bug (fwd)

Did anybody test these patches? Currently any user can crash the kernel by
abusing this bug.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

---------- Forwarded message ----------
Date: Sat, 14 Oct 2000 18:21:25 +0200 (CEST)
From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Samuel Rydh <samuel@ibrium.se>
Cc: Linux Frame Buffer Device Development <linux-fbdev@vuser.vu.union.edu>,
Linux/PPC Development <linuxppc-dev@lists.linuxppc.org>, olh@suse.de
Subject: Re: [linux-fbdev] Re: Video driver bug

On Sat, 7 Oct 2000, Geert Uytterhoeven wrote:
> On Sat, 7 Oct 2000, Samuel Rydh wrote:
> > Certain 2.4 video drivers (aty128, aty, platinum, tdfx, iga)
> > appear to be buggy. More specifically, the problem is the
> > following:
> >
> > In the set_disp function, info->dispsw is initialized and disp->dispsw
> > is given the address of info->dispsw:
> >
> > static void aty128_set_disp(..)
> > {
> > switch(bpp) {
> > case 8:
> > info->dispsw = accel ? fbcon_aty128_8 : fbcon_cfb8;
> > disp->dispsw = &info->dispsw;
> > break;
> > ...
> > }
> >
> > The problem is that the info struct is shared by all virtual consoles.
> > Thus if the video mode is set on a console which is not active, the
> > active console will be affected too. This typically results in a kernel
> > panic (the wrong set of console output functions is used).
>
> You're right. *_set_disp() may be called for non-active VTs, changing
> info->dispsw for the active VT.

Here are my fixes for aty128fb, atyfb, platinumfb, and tdfxfb.

Igafb is not affected since it sets disp during initialization only.

Can someone please test these patches so I can send them to Linus? I'm unable
to test any of them (besides a simple compile test). Thanks!

--- linux-dispsw-fix-2.4.0-test10-pre2/drivers/video/atyfb.c Sun Sep 17 20:04:17 2000
+++ geert-dispsw-fix-2.4.0-test10-pre2/drivers/video/atyfb.c Sat Oct 14 18:17:40 2000
@@ -466,8 +466,8 @@
static int encode_fix(struct fb_fix_screeninfo *fix,
const struct atyfb_par *par,
const struct fb_info_aty *info);
-static void atyfb_set_disp(struct display *disp, struct fb_info_aty *info,
- int bpp, int accel);
+static void atyfb_set_dispsw(struct display *disp, struct fb_info_aty *info,
+ int bpp, int accel);
static int atyfb_getcolreg(u_int regno, u_int *red, u_int *green, u_int *blue,
u_int *transp, struct fb_info *fb);
static int atyfb_setcolreg(u_int regno, u_int red, u_int green, u_int blue,
@@ -2826,8 +2826,8 @@
}


-static void atyfb_set_disp(struct display *disp, struct fb_info_aty *info,
- int bpp, int accel)
+static void atyfb_set_dispsw(struct display *disp, struct fb_info_aty *info,
+ int bpp, int accel)
{
switch (bpp) {
#ifdef FBCON_HAS_CFB8
@@ -2898,6 +2898,7 @@
oldbpp = display->var.bits_per_pixel;
oldaccel = display->var.accel_flags;
display->var = *var;
+ accel = var->accel_flags & FB_ACCELF_TEXT;
if (oldxres != var->xres || oldyres != var->yres ||
oldvxres != var->xres_virtual || oldvyres != var->yres_virtual ||
oldbpp != var->bits_per_pixel || oldaccel != var->accel_flags) {
@@ -2913,8 +2914,6 @@
display->line_length = fix.line_length;
display->can_soft_blank = 1;
display->inverse = 0;
- accel = var->accel_flags & FB_ACCELF_TEXT;
- atyfb_set_disp(display, info, par.crtc.bpp, accel);
if (accel)
display->scrollmode = (info->bus_type == PCI) ? SCROLL_YNOMOVE : 0;
else
@@ -2923,8 +2922,10 @@
(*info->fb_info.changevar)(con);
}
if (!info->fb_info.display_fg ||
- info->fb_info.display_fg->vc_num == con)
+ info->fb_info.display_fg->vc_num == con) {
atyfb_set_par(&par, info);
+ atyfb_set_dispsw(display, info, par.crtc.bpp, accel);
+ }
if (oldbpp != var->bits_per_pixel) {
if ((err = fb_alloc_cmap(&display->cmap, 0, 0)))
return err;
@@ -4241,8 +4242,8 @@

atyfb_decode_var(&fb_display[con].var, &par, info);
atyfb_set_par(&par, info);
- atyfb_set_disp(&fb_display[con], info, par.crtc.bpp,
- par.accel_flags & FB_ACCELF_TEXT);
+ atyfb_set_dispsw(&fb_display[con], info, par.crtc.bpp,
+ par.accel_flags & FB_ACCELF_TEXT);

/* Install new colormap */
do_install_cmap(con, fb);
--- linux-dispsw-fix-2.4.0-test10-pre2/drivers/video/tdfxfb.c Fri Jul 28 21:19:20 2000
+++ geert-dispsw-fix-2.4.0-test10-pre2/drivers/video/tdfxfb.c Sat Oct 14 17:29:21 2000
@@ -327,7 +327,6 @@
struct tdfxfb_par default_par;
struct tdfxfb_par current_par;
struct display disp;
- struct display_switch dispsw;
#if defined(FBCON_HAS_CFB16) || defined(FBCON_HAS_CFB24) || defined(FBCON_HAS_CFB32)
union {
#ifdef FBCON_HAS_CFB16
@@ -412,10 +411,10 @@
static int tdfxfb_encode_fix(struct fb_fix_screeninfo* fix,
const struct tdfxfb_par* par,
const struct fb_info_tdfx* info);
-static void tdfxfb_set_disp(struct display* disp,
- struct fb_info_tdfx* info,
- int bpp,
- int accel);
+static void tdfxfb_set_dispsw(struct display* disp,
+ struct fb_info_tdfx* info,
+ int bpp,
+ int accel);
static int tdfxfb_getcolreg(u_int regno,
u_int* red,
u_int* green,
@@ -1640,48 +1639,43 @@
return 0;
}

-static void tdfxfb_set_disp(struct display *disp,
- struct fb_info_tdfx *info,
- int bpp,
- int accel) {
+static void tdfxfb_set_dispsw(struct display *disp,
+ struct fb_info_tdfx *info,
+ int bpp,
+ int accel) {

if (disp->dispsw && disp->conp)
fb_con.con_cursor(disp->conp, CM_ERASE);
switch(bpp) {
#ifdef FBCON_HAS_CFB8
case 8:
- info->dispsw = noaccel ? fbcon_cfb8 : fbcon_banshee8;
- disp->dispsw = &info->dispsw;
+ disp->dispsw = noaccel ? &fbcon_cfb8 : &fbcon_banshee8;
if (nohwcursor) fbcon_banshee8.cursor = NULL;
break;
#endif
#ifdef FBCON_HAS_CFB16
case 16:
- info->dispsw = noaccel ? fbcon_cfb16 : fbcon_banshee16;
- disp->dispsw = &info->dispsw;
+ disp->dispsw = noaccel ? &fbcon_cfb16 : &fbcon_banshee16;
disp->dispsw_data = info->fbcon_cmap.cfb16;
if (nohwcursor) fbcon_banshee16.cursor = NULL;
break;
#endif
#ifdef FBCON_HAS_CFB24
case 24:
- info->dispsw = noaccel ? fbcon_cfb24 : fbcon_banshee24;
- disp->dispsw = &info->dispsw;
+ disp->dispsw = noaccel ? &fbcon_cfb24 : &fbcon_banshee24;
disp->dispsw_data = info->fbcon_cmap.cfb24;
if (nohwcursor) fbcon_banshee24.cursor = NULL;
break;
#endif
#ifdef FBCON_HAS_CFB32
case 32:
- info->dispsw = noaccel ? fbcon_cfb32 : fbcon_banshee32;
- disp->dispsw = &info->dispsw;
+ disp->dispsw = noaccel ? &fbcon_cfb32 : &fbcon_banshee32;
disp->dispsw_data = info->fbcon_cmap.cfb32;
if (nohwcursor) fbcon_banshee32.cursor = NULL;
break;
#endif
default:
- info->dispsw = fbcon_dummy;
- disp->dispsw = &info->dispsw;
+ disp->dispsw = &fbcon_dummy;
}

}
@@ -1735,7 +1729,7 @@
display->can_soft_blank = 1;
display->inverse = inverse;
accel = var->accel_flags & FB_ACCELF_TEXT;
- tdfxfb_set_disp(display, info, par.bpp, accel);
+ tdfxfb_set_dispsw(display, info, par.bpp, accel);

if(nopan) display->scrollmode = SCROLL_YREDRAW;

@@ -2083,10 +2077,10 @@

info->cursor.redraw=1;

- tdfxfb_set_disp(&fb_display[con],
- info,
- par.bpp,
- par.accel_flags & FB_ACCELF_TEXT);
+ tdfxfb_set_dispsw(&fb_display[con],
+ info,
+ par.bpp,
+ par.accel_flags & FB_ACCELF_TEXT);

tdfxfb_install_cmap(&fb_display[con], fb);
tdfxfb_updatevar(con, fb);
--- linux-dispsw-fix-2.4.0-test10-pre2/drivers/video/aty128fb.c Sun Sep 17 20:04:17 2000
+++ geert-dispsw-fix-2.4.0-test10-pre2/drivers/video/aty128fb.c Sat Oct 14 17:32:10 2000
@@ -283,7 +283,6 @@
const struct aty128_meminfo *mem; /* onboard mem info */
struct aty128fb_par default_par, current_par;
struct display disp;
- struct display_switch dispsw; /* for cursor and font */
struct { u8 red, green, blue, pad; } palette[256];
union {
#ifdef FBCON_HAS_CFB16
@@ -347,7 +346,7 @@
static void aty128_encode_fix(struct fb_fix_screeninfo *fix,
struct aty128fb_par *par,
const struct fb_info_aty128 *info);
-static void aty128_set_disp(struct display *disp,
+static void aty128_set_dispsw(struct display *disp,
struct fb_info_aty128 *info, int bpp, int accel);
static int aty128_getcolreg(u_int regno, u_int *red, u_int *green, u_int *blue,
u_int *transp, struct fb_info *info);
@@ -1392,7 +1391,7 @@
display->inverse = 0;

accel = var->accel_flags & FB_ACCELF_TEXT;
- aty128_set_disp(display, info, par.crtc.bpp, accel);
+ aty128_set_dispsw(display, info, par.crtc.bpp, accel);

if (accel)
display->scrollmode = SCROLL_YNOMOVE;
@@ -1417,35 +1416,31 @@


static void
-aty128_set_disp(struct display *disp,
+aty128_set_dispsw(struct display *disp,
struct fb_info_aty128 *info, int bpp, int accel)
{
switch (bpp) {
#ifdef FBCON_HAS_CFB8
case 8:
- info->dispsw = accel ? fbcon_aty128_8 : fbcon_cfb8;
- disp->dispsw = &info->dispsw;
+ disp->dispsw = accel ? &fbcon_aty128_8 : &fbcon_cfb8;
break;
#endif
#ifdef FBCON_HAS_CFB16
case 15:
case 16:
- info->dispsw = accel ? fbcon_aty128_16 : fbcon_cfb16;
- disp->dispsw = &info->dispsw;
+ disp->dispsw = accel ? &fbcon_aty128_16 : &fbcon_cfb16;
disp->dispsw_data = info->fbcon_cmap.cfb16;
break;
#endif
#ifdef FBCON_HAS_CFB24
case 24:
- info->dispsw = accel ? fbcon_aty128_24 : fbcon_cfb24;
- disp->dispsw = &info->dispsw;
+ disp->dispsw = accel ? &fbcon_aty128_24 : &fbcon_cfb24;
disp->dispsw_data = info->fbcon_cmap.cfb24;
break;
#endif
#ifdef FBCON_HAS_CFB32
case 32:
- info->dispsw = accel ? fbcon_aty128_32 : fbcon_cfb32;
- disp->dispsw = &info->dispsw;
+ disp->dispsw = accel ? &fbcon_aty128_32 : &fbcon_cfb32;
disp->dispsw_data = info->fbcon_cmap.cfb32;
break;
#endif
@@ -2135,7 +2130,7 @@
aty128_decode_var(&fb_display[con].var, &par, info);
aty128_set_par(&par, info);

- aty128_set_disp(&fb_display[con], info, par.crtc.bpp,
+ aty128_set_dispsw(&fb_display[con], info, par.crtc.bpp,
par.accel_flags & FB_ACCELF_TEXT);

do_install_cmap(con, fb);
--- linux-dispsw-fix-2.4.0-test10-pre2/drivers/video/platinumfb.c Sat Aug 5 14:20:03 2000
+++ geert-dispsw-fix-2.4.0-test10-pre2/drivers/video/platinumfb.c Sat Oct 14 17:30:22 2000
@@ -65,7 +65,6 @@
struct fb_info_platinum {
struct fb_info fb_info;
struct display disp;
- struct display_switch dispsw;
struct fb_par_platinum default_par;
struct fb_par_platinum current_par;

@@ -140,8 +139,9 @@
static int platinum_encode_fix(struct fb_fix_screeninfo *fix,
const struct fb_par_platinum *par,
const struct fb_info_platinum *info);
-static void platinum_set_disp(struct display *disp, struct fb_info_platinum *info,
- int cmode, int accel);
+static void platinum_set_dispsw(struct display *disp,
+ struct fb_info_platinum *info, int cmode,
+ int accel);
static int platinum_getcolreg(u_int regno, u_int *red, u_int *green, u_int *blue,
u_int *transp, struct fb_info *fb);
static int platinum_setcolreg(u_int regno, u_int red, u_int green, u_int blue,
@@ -193,27 +193,25 @@
return 0;
}

-static void platinum_set_disp(struct display *disp, struct fb_info_platinum *info,
- int cmode, int accel)
+static void platinum_set_dispsw(struct display *disp,
+ struct fb_info_platinum *info, int cmode,
+ int accel)
{
switch(cmode) {
#ifdef FBCON_HAS_CFB8
case CMODE_8:
- info->dispsw = fbcon_cfb8;
- disp->dispsw = &info->dispsw;
+ disp->dispsw = &fbcon_cfb8;
break;
#endif
#ifdef FBCON_HAS_CFB16
case CMODE_16:
- info->dispsw = fbcon_cfb16;
- disp->dispsw = &info->dispsw;
+ disp->dispsw = &fbcon_cfb16;
disp->dispsw_data = info->fbcon_cmap.cfb16;
break;
#endif
#ifdef FBCON_HAS_CFB32
case CMODE_32:
- info->dispsw = fbcon_cfb32;
- disp->dispsw = &info->dispsw;
+ disp->dispsw = &fbcon_cfb32;
disp->dispsw_data = info->fbcon_cmap.cfb32;
break;
#endif
@@ -271,7 +269,7 @@
display->line_length = fix.line_length;
display->can_soft_blank = 1;
display->inverse = 0;
- platinum_set_disp(display, info, par.cmode, 0);
+ platinum_set_dispsw(display, info, par.cmode, 0);
display->scrollmode = SCROLL_YREDRAW;
if (info->fb_info.changevar)
(*info->fb_info.changevar)(con);
@@ -341,7 +339,7 @@

platinum_var_to_par(&fb_display[con].var, &par, info);
platinum_set_par(&par, info);
- platinum_set_disp(&fb_display[con], info, par.cmode, 0);
+ platinum_set_dispsw(&fb_display[con], info, par.cmode, 0);
do_install_cmap(con, fb);

return 1;
Gr{oetje,eeting}s,
Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds


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