diff options
author | Helge Deller <deller@gmx.de> | 2022-06-25 13:00:34 +0200 |
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committer | Helge Deller <deller@gmx.de> | 2022-07-07 10:50:46 +0200 |
commit | e64242caef18b4a5840b0e7a9bff37abd4f4f933 (patch) | |
tree | be18c49db4dbefbfa6afe060abe7fd645c6b9e3a /drivers/video/fbdev/core/fbcon.c | |
parent | fbcon: Disallow setting font bigger than screen size (diff) | |
download | linux-stable-e64242caef18b4a5840b0e7a9bff37abd4f4f933.tar.xz linux-stable-e64242caef18b4a5840b0e7a9bff37abd4f4f933.zip |
fbcon: Prevent that screen size is smaller than font size
We need to prevent that users configure a screen size which is smaller than the
currently selected font size. Otherwise rendering chars on the screen will
access memory outside the graphics memory region.
This patch adds a new function fbcon_modechange_possible() which
implements this check and which later may be extended with other checks
if necessary. The new function is called from the FBIOPUT_VSCREENINFO
ioctl handler in fbmem.c, which will return -EINVAL if userspace asked
for a too small screen size.
Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: stable@vger.kernel.org # v5.4+
Diffstat (limited to 'drivers/video/fbdev/core/fbcon.c')
-rw-r--r-- | drivers/video/fbdev/core/fbcon.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index a33532564393..5632870a9aeb 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2736,6 +2736,34 @@ void fbcon_update_vcs(struct fb_info *info, bool all) } EXPORT_SYMBOL(fbcon_update_vcs); +/* let fbcon check if it supports a new screen resolution */ +int fbcon_modechange_possible(struct fb_info *info, struct fb_var_screeninfo *var) +{ + struct fbcon_ops *ops = info->fbcon_par; + struct vc_data *vc; + unsigned int i; + + WARN_CONSOLE_UNLOCKED(); + + if (!ops) + return 0; + + /* prevent setting a screen size which is smaller than font size */ + for (i = first_fb_vc; i <= last_fb_vc; i++) { + vc = vc_cons[i].d; + if (!vc || vc->vc_mode != KD_TEXT || + registered_fb[con2fb_map[i]] != info) + continue; + + if (vc->vc_font.width > FBCON_SWAP(var->rotate, var->xres, var->yres) || + vc->vc_font.height > FBCON_SWAP(var->rotate, var->yres, var->xres)) + return -EINVAL; + } + + return 0; +} +EXPORT_SYMBOL_GPL(fbcon_modechange_possible); + int fbcon_mode_deleted(struct fb_info *info, struct fb_videomode *mode) { |