From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="M9Rgjoxa" Received: from out-185.mta1.migadu.com (out-185.mta1.migadu.com [IPv6:2001:41d0:203:375::b9]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DDBA2D5 for ; Wed, 13 Dec 2023 04:15:32 -0800 (PST) Message-ID: <78c25a62-44d5-d40d-a3e8-1f40a0c95c11@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1702469278; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DU7Ue/NZBO61kVWg5eFser6LJMK31DbbsBvBIKnZORg=; b=M9Rgjoxa+lySX3pH1qW05LzgbxUlUivYz+67rZWH7OnWNUGzpfJfodxrwxDf3aTZGSjyCh Gym/H14JCLFf7PtGmTW1bLpnkva18xTx4uSPQInOeIZiqMtOLtahvjjkmIV9kBQ1GVdIcy clznz3LNmOcfVDly6+Iuj6mCQcqxQ+0= Date: Wed, 13 Dec 2023 20:07:51 +0800 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH] block/rnbd-srv: Check for unlikely string overflow To: Kees Cook , "Md. Haris Iqbal" Cc: kernel test robot , Jack Wang , Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org References: <20231212214738.work.169-kees@kernel.org> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Guoqing Jiang In-Reply-To: <20231212214738.work.169-kees@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 12/13/23 05:47, Kees Cook wrote: > Since "dev_search_path" can technically be as large as PATH_MAX, > there was a risk of truncation when copying it and a second string > into "full_path" since it was also PATH_MAX sized. The W=1 builds were > reporting this warning: > > drivers/block/rnbd/rnbd-srv.c: In function 'process_msg_open.isra': > drivers/block/rnbd/rnbd-srv.c:616:51: warning: '%s' directive output may be truncated writing up to 254 bytes into a region of size between 0 and 4095 [-Wformat-truncation=] > 616 | snprintf(full_path, PATH_MAX, "%s/%s", > | ^~ > In function 'rnbd_srv_get_full_path', > inlined from 'process_msg_open.isra' at drivers/block/rnbd/rnbd-srv.c:721:14: drivers/block/rnbd/rnbd-srv.c:616:17: note: 'snprintf' output between 2 and 4351 bytes into a destination of size 4096 > 616 | snprintf(full_path, PATH_MAX, "%s/%s", > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > 617 | dev_search_path, dev_name); > | ~~~~~~~~~~~~~~~~~~~~~~~~~~ > > To fix this, unconditionally check for truncation (as was already done > for the case where "%SESSNAME%" was present). > > Reported-by: kernel test robot > Closes: https://lore.kernel.org/oe-kbuild-all/202312100355.lHoJPgKy-lkp@intel.com/ > Cc: "Md. Haris Iqbal" > Cc: Jack Wang > Cc: Jens Axboe > Cc: linux-block@vger.kernel.org > Signed-off-by: Kees Cook > --- > drivers/block/rnbd/rnbd-srv.c | 19 ++++++++++--------- > 1 file changed, 10 insertions(+), 9 deletions(-) > > diff --git a/drivers/block/rnbd/rnbd-srv.c b/drivers/block/rnbd/rnbd-srv.c > index 65de51f3dfd9..ab78eab97d98 100644 > --- a/drivers/block/rnbd/rnbd-srv.c > +++ b/drivers/block/rnbd/rnbd-srv.c > @@ -585,6 +585,7 @@ static char *rnbd_srv_get_full_path(struct rnbd_srv_session *srv_sess, > { > char *full_path; > char *a, *b; > + int len; > > full_path = kmalloc(PATH_MAX, GFP_KERNEL); > if (!full_path) > @@ -596,19 +597,19 @@ static char *rnbd_srv_get_full_path(struct rnbd_srv_session *srv_sess, > */ > a = strnstr(dev_search_path, "%SESSNAME%", sizeof(dev_search_path)); > if (a) { > - int len = a - dev_search_path; > + len = a - dev_search_path; > > len = snprintf(full_path, PATH_MAX, "%.*s/%s/%s", len, > dev_search_path, srv_sess->sessname, dev_name); > - if (len >= PATH_MAX) { > - pr_err("Too long path: %s, %s, %s\n", > - dev_search_path, srv_sess->sessname, dev_name); > - kfree(full_path); > - return ERR_PTR(-EINVAL); > - } > } else { > - snprintf(full_path, PATH_MAX, "%s/%s", > - dev_search_path, dev_name); > + len = snprintf(full_path, PATH_MAX, "%s/%s", > + dev_search_path, dev_name); > + } > + if (len >= PATH_MAX) { > + pr_err("Too long path: %s, %s, %s\n", > + dev_search_path, srv_sess->sessname, dev_name); > + kfree(full_path); > + return ERR_PTR(-EINVAL); > } > > /* eliminitate duplicated slashes */ Looks good. Acked-by: Guoqing Jiang