From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> stable inclusion from linux-4.19.207 commit 5f87c22d3dd91795590524ba69bb4368f8957a72 -------------------------------- commit 8c28051cdcbe9dfcec6bd0a4709d67a09df6edae upstream. 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-b07092... Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- drivers/video/fbdev/core/fbmem.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index de04c097d67c7..2297dfb494d6a 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -971,6 +971,7 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var) if ((var->activate & FB_ACTIVATE_FORCE) || memcmp(&info->var, var, sizeof(struct fb_var_screeninfo))) { u32 activate = var->activate; + u32 unused; /* When using FOURCC mode, make sure the red, green, blue and * transp fields are set to 0. @@ -995,6 +996,11 @@ 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) -- 2.25.1