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authorTetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>2021-09-08 19:27:49 +0900
committerDaniel Vetter <daniel.vetter@ffwll.ch>2021-09-08 18:52:04 +0200
commit8c28051cdcbe9dfcec6bd0a4709d67a09df6edae (patch)
treebf98d1945cca9a2268bff4715044a3542b5d666f
parent87fd9ef47597b2fcee3264eb5f288410b9f376d5 (diff)
fbmem: don't allow too huge resolutionsdrm-misc-next-fixes-2021-09-09
syzbot is reporting page fault at vga16fb_fillrect() [1], for vga16fb_check_var() is failing to detect multiplication overflow. if (vxres * vyres > maxmem) { vyres = maxmem / vxres; if (vyres < yres) return -ENOMEM; } Since no module would accept too huge resolutions where multiplication overflow happens, let's reject in the common path. Link: https://syzkaller.appspot.com/bug?extid=04168c8063cfdde1db5e [1] Reported-by: syzbot <syzbot+04168c8063cfdde1db5e@syzkaller.appspotmail.com> Debugged-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> Cc: stable@vger.kernel.org Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/185175d6-227a-7b55-433d-b070929b262c@i-love.sakura.ne.jp
-rw-r--r--drivers/video/fbdev/core/fbmem.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 71fb710f1ce3..7420d2c16e47 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -962,6 +962,7 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
struct fb_var_screeninfo old_var;
struct fb_videomode mode;
struct fb_event event;
+ u32 unused;
if (var->activate & FB_ACTIVATE_INV_MODE) {
struct fb_videomode mode1, mode2;
@@ -1008,6 +1009,11 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
if (var->xres < 8 || var->yres < 8)
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))
+ return -EINVAL;
+
ret = info->fbops->fb_check_var(var, info);
if (ret)