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authorHelge Deller <deller@gmx.de>2022-06-25 14:00:34 +0300
committerHelge Deller <deller@gmx.de>2022-07-07 11:50:46 +0300
commite64242caef18b4a5840b0e7a9bff37abd4f4f933 (patch)
treebe18c49db4dbefbfa6afe060abe7fd645c6b9e3a /drivers/video
parent65a01e601dbba8b7a51a2677811f70f783766682 (diff)
downloadlinux-e64242caef18b4a5840b0e7a9bff37abd4f4f933.tar.xz
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')
-rw-r--r--drivers/video/fbdev/core/fbcon.c28
-rw-r--r--drivers/video/fbdev/core/fbmem.c4
2 files changed, 31 insertions, 1 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)
{
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index ee63b5b47290..7dc6848a96bb 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1107,7 +1107,9 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
return -EFAULT;
console_lock();
lock_fb_info(info);
- ret = fb_set_var(info, &var);
+ ret = fbcon_modechange_possible(info, &var);
+ if (!ret)
+ ret = fb_set_var(info, &var);
if (!ret)
fbcon_update_vcs(info, var.activate & FB_ACTIVATE_ALL);
unlock_fb_info(info);