From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Carpenter Date: Wed, 27 Oct 2010 09:37:16 +0000 Subject: [RFC] [patch] fbcmap: integer overflow bug Message-Id: <20101027093716.GD6062@bicker> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-fbdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org There is an integer overflow bug in the FBIOPUTCMAP ioctl if cmap->len * 2 overflows. It's harmless, except that it messes up the cmap until someone types `reset`. It could have been caught by checking the return from fb_copy_cmap(). Or it could have been caught by limiting the size of the cmaps to one page. The cmaps are allocated with GFP_ATOMIC and it makes sense to limit them. Different drivers use different sizes of cmaps. There are about 150 drivers. I've checked a bunch (50) of them and the larges cmap.len I've found is gxt4500 which maxes out at 1024 so PAGE_SIZE is about twice that length. For some of the 50 I wasn't sure on the limit. Is PAGE_SIZE a reasonable limit? Does anyone know or do I have to audit all 150 drivers? diff --git a/drivers/video/fbcmap.c b/drivers/video/fbcmap.c index f53b9f1..6dc5817 100644 --- a/drivers/video/fbcmap.c +++ b/drivers/video/fbcmap.c @@ -110,7 +110,9 @@ int fb_alloc_cmap(struct fb_cmap *cmap, int len, int transp) } cmap->start = 0; cmap->len = len; - fb_copy_cmap(fb_default_cmap(len), cmap); + if (fb_copy_cmap(fb_default_cmap(len), cmap)) + goto fail; + return 0; fail: @@ -250,6 +252,9 @@ int fb_set_user_cmap(struct fb_cmap_user *cmap, struct fb_info *info) int rc, size = cmap->len * sizeof(u16); struct fb_cmap umap; + if (cmap->len > PAGE_SIZE || cmap->len * sizeof(u16) > PAGE_SIZE) + return -EINVAL; + memset(&umap, 0, sizeof(struct fb_cmap)); rc = fb_alloc_cmap(&umap, cmap->len, cmap->transp != NULL); if (rc)