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authorTetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>2021-09-08 19:27:49 +0900
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-09-15 09:47:41 +0200
commit5de2ee621bc48fc527f0ed51265eea4bed8b769a (patch)
tree3389acabe4f8d3051ecfcbc3ed24addb6d25e145
parent4a95b04afab55ecac3f4b71a61e7ef6dcbfb892f (diff)
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fbmem: don't allow too huge resolutions
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-b070929b262c@i-love.sakura.ne.jp Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-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 d87de5d46718..03b1bf994cc9 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -957,6 +957,7 @@ 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;
@@ -1003,6 +1004,11 @@ 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)