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| author | Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> | 2021-09-08 19:27:49 +0900 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2021-09-08 18:52:04 +0200 |
| commit | 8c28051cdcbe9dfcec6bd0a4709d67a09df6edae (patch) | |
| tree | bf98d1945cca9a2268bff4715044a3542b5d666f | |
| parent | 87fd9ef47597b2fcee3264eb5f288410b9f376d5 (diff) | |
| download | linux-8c28051cdcbe9dfcec6bd0a4709d67a09df6edae.tar.gz linux-8c28051cdcbe9dfcec6bd0a4709d67a09df6edae.tar.bz2 linux-8c28051cdcbe9dfcec6bd0a4709d67a09df6edae.zip | |
fbmem: don't allow too huge resolutions
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.c | 6 |
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) |