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[v5,2/4] fbmem: Prevent invalid virtual screen sizes

Message ID 20220626085615.53728-3-deller@gmx.de
State Superseded
Headers show
Series fbcon: Fixes for screen resolution changes | expand

Commit Message

Helge Deller June 26, 2022, 8:56 a.m. UTC 
Prevent that drivers or the user sets the virtual screen resolution
smaller than the physical screen resolution.  This is important, because
otherwise we may access memory outside of the graphics memory area.

Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org # v5.4+
---
 drivers/video/fbdev/core/fbmem.c | 6 ++++++
 1 file changed, 6 insertions(+)

--
2.35.3
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Patch

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index afa2863670f3..5dfa4bbee642 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1006,6 +1006,12 @@  fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
 	if (var->xres < 8 || var->yres < 8)
 		return -EINVAL;

+	/* make sure virtual resolution >= physical resolution */
+	if (var->xres_virtual < var->xres)
+		return -EINVAL;
+	if (var->yres_virtual < var->yres)
+		return -EINVAL;
+
 	/* Too huge resolution causes multiplication overflow. */
 	if (check_mul_overflow(var->xres, var->yres, &unused) ||
 	    check_mul_overflow(var->xres_virtual, var->yres_virtual, &unused))