From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 53FFE169398; Wed, 29 May 2024 10:17:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716977841; cv=none; b=IA35yUQLo2gKJbUOOJyich++2EHTnX+9RWM7Lvgcu5CM8JzJm0wNnvyLLYDstdqFv4GGqEG5jX3YJw7ScOZXKjmyh0mCSPsa762uBcnU7bscMePUndfV2wfrDZZm6BSO74LUXtxMSBAFVA4reqOoplT0LMBBQGZUGhZYITEDTBw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716977841; c=relaxed/simple; bh=Czi949DADm29y+/uucQdHueJL3drBx5CNw5SdCX8sF0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=m3gAXTyWjllAKbETSVx/9lDVQWUrXQERixd+JcbCz5eanKHP8SotbR5KPglVVQnQekbSw0ul2F+iNFsK+mano5GNJ4jwFvB60zI+Rsw6L0o4cwp2NgAhJI/ynpN1B5TYhwddCHdqKEKAUSzJ2Kam1uEj0JdWZCQnEcCG8wgS0M8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vqbtRrgQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="vqbtRrgQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7D510C2BD10; Wed, 29 May 2024 10:17:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1716977840; bh=Czi949DADm29y+/uucQdHueJL3drBx5CNw5SdCX8sF0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=vqbtRrgQMOdFub4BijLES/067YvaOGoLwh7IJe/Caeeoaptw3gdKlQwdAD/1kJqCz 9Ff9wto4/kpBPdFTmT6j1aVs7HrJp1oyKximLnt8C0ZpxdPctKHSfCtKZV2Ea21ViR jOAOes1gXrnrAlTQ1T9NnCgaZdW/9xV0M9L2jNbg= Date: Wed, 29 May 2024 12:17:09 +0200 From: Greg KH To: quic_zijuhu Cc: Dmitry Torokhov , rafael@kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] kobject_uevent: Fix OOB access within zap_modalias_env() Message-ID: <2024052933-extended-spender-fc41@gregkh> References: <1716866347-11229-1-git-send-email-quic_zijuhu@quicinc.com> <74e2db16-007a-4b31-b43d-649516000f16@quicinc.com> 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-Disposition: inline In-Reply-To: <74e2db16-007a-4b31-b43d-649516000f16@quicinc.com> On Wed, May 29, 2024 at 06:07:06PM +0800, quic_zijuhu wrote: > On 5/29/2024 2:56 AM, Dmitry Torokhov wrote: > > On Tue, May 28, 2024 at 11:19:07AM +0800, Zijun Hu wrote: > >> zap_modalias_env() wrongly calculates size of memory block to move, so > >> will cause OOB memory access issue if variable MODALIAS is not the last > >> one within its @env parameter, fixed by correcting size to memmove. > >> > >> Fixes: 9b3fa47d4a76 ("kobject: fix suppressing modalias in uevents delivered over netlink") > >> Cc: stable@vger.kernel.org > >> Signed-off-by: Zijun Hu > >> --- > >> V1 -> V2: Correct commit messages and add inline comments > >> > >> V1 discussion link: > >> https://lore.kernel.org/lkml/0b916393-eb39-4467-9c99-ac1bc9746512@quicinc.com/T/#m8d80165294640dbac72f5c48d14b7ca4f097b5c7 > >> > >> lib/kobject_uevent.c | 17 ++++++++++++++++- > >> 1 file changed, 16 insertions(+), 1 deletion(-) > >> > >> diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c > >> index 03b427e2707e..f22366be020c 100644 > >> --- a/lib/kobject_uevent.c > >> +++ b/lib/kobject_uevent.c > >> @@ -433,8 +433,23 @@ static void zap_modalias_env(struct kobj_uevent_env *env) > >> len = strlen(env->envp[i]) + 1; > >> > >> if (i != env->envp_idx - 1) { > >> + /* @env->envp[] contains pointers to @env->buf[] > >> + * with @env->buflen elements, and we want to > >> + * remove variable MODALIAS pointed by > >> + * @env->envp[i] with length @len as shown below: > >> + * > >> + * 0 @env->buf[] @env->buflen > >> + * ---------------------------------------- > >> + * ^ ^ ^ > >> + * |-> @len <-| target block | > >> + * @env->envp[i] @env->envp[i+1] > >> + * > >> + * so the "target block" indicated above is moved > >> + * backward by @len, and its right size is > >> + * (@env->buf + @env->buflen - @env->envp[i + 1]). > >> + */ > >> memmove(env->envp[i], env->envp[i + 1], > >> - env->buflen - len); > >> + env->buf + env->buflen - env->envp[i + 1]); > > > > Thank you for noticing this, it is indeed a bug. > > > > I wonder if this would not be expressed better as: > > > > tail_len = env->buflen - (env->envp[i + 1] - env->envp[0]); > > memmove(env->envp[i], env->envp[i + 1], tail_len); > > > > and we would not need the large comment. > > > Greg KH suggests add inline comments since my fix is not obvious with > first glance, let us wait for his comments within 2 days about below > question: > is it okay to remove those inline comments if block size to move is > changed to env->buflen - (env->envp[i + 1] - env->envp[0]) ? I'm all for making this simpler, please do so as Dmitry's response looks better and easier to understand, don't you think? And add comments, they are always good here for stuff like this :) thanks, greg k-h