From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f48.google.com (mail-wm1-f48.google.com [209.85.128.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 409CC3D668E for ; Wed, 18 Mar 2026 15:12:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773846775; cv=none; b=vCsMhgaXSiGGBQ3VJ5prHtVXwv9r4gWBsh2cK+8SZKTTF72sjksuSNPutp0z5BxEiL18swvAOQcpYXda4snSPu34KYpsSmFQ5ZK8haZI4kIQN1LZOZ1rUea5dMelBG/ybhz8e/iuVdXMO30+jdytLNeu0pHxiD0l0cOBYgyWPKg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773846775; c=relaxed/simple; bh=1AB665uQu3ZGDCKPAtF0lHKxykcrXaiq4mRGceFg65o=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=movnsj0ielwG/FqTDA7qq5Dofe4wFs2mtGiNneTmhDUzpDCwGlf6zRZ/xw40Sa8L3It8qkmLJa0zB/4xIob98xZPRa/gOLiW9fr471o5cpnPktpewNNaWMAbJQuDJslmowCG8RQZ8mTKGcFMhyep/U/93Ah1kI/GEM2HOUKrqW0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=WI2r0yxu; arc=none smtp.client-ip=209.85.128.48 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WI2r0yxu" Received: by mail-wm1-f48.google.com with SMTP id 5b1f17b1804b1-4852fdb36a8so81530545e9.2 for ; Wed, 18 Mar 2026 08:12:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1773846773; x=1774451573; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=exM1Iff+xUWC3C9H/16DKULzTAM9igYujLmwE9sN/Ws=; b=WI2r0yxuVvc4jBlZndmJLrnivwwpA6G8jQq+2/B9NpDSxJBtxBFAqQ3zEuzkGFRzhE uy53E5qjgwcJJyBz//edIGAN4MPWUnzoq3Pjl1UY+1OQAFgUhZ5UX81avPqmqpn8f1iE N8xpRSKXvY6eKD9VWafY1Qb45cYiSeypePhRbxYrgtGHvUO309dq47gwqpbwF6kh2UeN aUBmJCmh+u4+I5JRoPaEA7Gop2CxeimOPwbLCdWihyhrAFWAXIejDW+uSbciGJdDqo5r OpamHiiP8NoyKg/j+2fRrC2s3aQ49KqhqSlDT5DdRPoJnbBhMJHePFZSW5k4kM4BP6eZ eY2A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1773846773; x=1774451573; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=exM1Iff+xUWC3C9H/16DKULzTAM9igYujLmwE9sN/Ws=; b=ro3qK5Npxv1od85mw615GbwOtli9qxzcd2NvsAEBp8KrzN130U7OI8WSZWwhFkFF4/ R3Us4nz5zr199+ajKXHos/+reGzD5PQ6924prBvg1oe/Hgh0LcAR4XVqbglDvavkDK4K Lx4MmVv1C7SjNQP+a1nrk37wh9pXgJAxwmJpKxckhTeHnfu5fta+/oyQWCp7Ws0q1vKu rsAUImjo0bmrRUoiNYKyAoJK9KxK69vGYQeEQ4DSfzcgZUbPTwHC/UNEBvzqQbTt78eD oGxzFYyWDvZ49ha5/l/oQfvzgE3aQ5E57aiB/kKpDLOo6R9bGgkKgIvsoV1itfYFKpB7 Rmww== X-Forwarded-Encrypted: i=1; AJvYcCV8MuQ03FL8mgMStp8FmDl8yQ/tUbOZ8UZDNlN8sjKR9Wg87KcldOZEjNpgOIKfLUxzETII8mquIWuUD6w=@vger.kernel.org X-Gm-Message-State: AOJu0YxzaUM/g9e0/cYQ+l5G6oU9IJ9CAG/JjHDzismVKigKPUWrRwVD /lGPvrVmBSgw6/a5qKj4qSzLBymUEHiKdrEchOIPaEsyRBJFtok8OXnt X-Gm-Gg: ATEYQzxs324iLvHdegXCUqsZVH/ud5qq5mGccjjw6Oj/j6iiCrR1H3MFptBfeOAChl1 2wf1nE54byN/Kv2f3SK501ZWGYBea9KBLvwFjQP0rj9GNAuWdRHOf0t61+KLuznJJdQ1nf5m9FS AT+UoubanrjanYl0nUPrvRPW/DfeUXd2+RbHP/d3BR6gSyaX1O81ZTkRclrGoSSF0+CGwxyGPE2 XlrBr/jh0PBANtt/BHuDLXaWlnGqeIN3sAQZzp5fvwUTtnCrUNDhDRdfYc5y8GX10aImjE5fHY1 3OS+NEmvfIQyFD0PKHHXyb2RCjqgxCh4UrpTbqpsFbJmC9jbOMWGDU3iH7mpcCWp8D8QCZZoRXw KETFd3jjJKKd9yr66yoUEjhDulHVDMWrcRIVzAzjJMYeWSPFvYhk3vmWw1qgcbUVgRzMRBaEwLA Po0Y6el0aVWt8CcooswtbMR8qSQqFDRFf08NWto1ICfFEp4xwZdbTbjqcpaUPOEFgXQEZJ/vhP3 KE= X-Received: by 2002:a05:600c:630f:b0:485:531d:28b9 with SMTP id 5b1f17b1804b1-486f443841amr64877395e9.14.1773846772381; Wed, 18 Mar 2026 08:12:52 -0700 (PDT) Received: from pumpkin (82-69-66-36.dsl.in-addr.zen.co.uk. [82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-486f421a617sm81548895e9.7.2026.03.18.08.12.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2026 08:12:52 -0700 (PDT) Date: Wed, 18 Mar 2026 15:12:50 +0000 From: David Laight To: Steven Rostedt Cc: "Masami Hiramatsu (Google)" , Ard Biesheuvel , Ilias Apalodimas , Josh Law , Andrew Morton , linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 1/1] lib/vsprintf: Limit the returning size to INT_MAX Message-ID: <20260318151250.40fef0ab@pumpkin> In-Reply-To: <20260318094733.1ada0513@gandalf.local.home> References: <177379678638.535490.18200744206158553364.stgit@devnote2> <177379679625.535490.15253547806594621828.stgit@devnote2> <20260318094733.1ada0513@gandalf.local.home> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 18 Mar 2026 09:47:33 -0400 Steven Rostedt wrote: > On Wed, 18 Mar 2026 10:19:56 +0900 > "Masami Hiramatsu (Google)" wrote: > > > From: Masami Hiramatsu (Google) > > > > There seems a design flaw of vsnprintf() whose return value can > > overflow the INT_MAX even on 32bit arch, because the buffer size is > > passed by 'size_t' but it returns the printed or required size in 'int'. > > > > The size_t is unsigned long, thus the caller can pass bigger than INT_MAX > > as the size of buffer (that is OK). But even the vsnprintf calculates > > the required/printed length correctly, if it overflows the INT_MAX, > > it can not return the size correctly by int. > > > > This should never happen but it should be checked and limited. > > > > Signed-off-by: Masami Hiramatsu (Google) > > --- > > drivers/firmware/efi/libstub/vsprintf.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/firmware/efi/libstub/vsprintf.c b/drivers/firmware/efi/libstub/vsprintf.c > > index 71c71c222346..1713cacecc25 100644 > > --- a/drivers/firmware/efi/libstub/vsprintf.c > > +++ b/drivers/firmware/efi/libstub/vsprintf.c > > @@ -549,7 +549,7 @@ int vsnprintf(char *buf, size_t size, const char *fmt, va_list ap) > > if (size) > > buf[min(pos, size-1)] = '\0'; > > > > - return pos; > > + return (pos > INT_MAX) ? INT_MAX : pos; > > } > > > > int snprintf(char *buf, size_t size, const char *fmt, ...) > > Since this would require a buffer of size greater than 2G to be passed in, > I highly doubt this would happen anywhere in the kernel. > > If anything, it would be for "correctness" only, but I don't see this ever > being an issue within this century. What about the return value (on 32bit) from: snprintf(NULL, 0, " %*s %*s ", INT_MAX, "", INT_MAX, ""); This is more of a problem for libc. In reality there are easier ways to crash the kernel.... David > > -- Steve >