Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Sat, 29 Jul 2023 09:29:33 +0200
From:   Willy Tarreau <w@1wt.eu>
To:     Thomas =?iso-8859-1?Q?Wei=DFschuh?= <linux@weissschuh.net>
Cc:     Shuah Khan <shuah@kernel.org>, Zhangjin Wu <falcon@tinylab.org>,
        linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] selftests/nolibc: avoid buffer underrun in space printing
Message-ID: <20230729072933.GF956@1wt.eu>
References: <20230726-nolibc-result-width-v1-1-d1d2dc21844e@weissschuh.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20230726-nolibc-result-width-v1-1-d1d2dc21844e@weissschuh.net>
User-Agent: Mutt/1.10.1 (2018-07-13)
Precedence: bulk

On Wed, Jul 26, 2023 at 08:08:13AM +0200, Thomas Wei?schuh wrote:
> If the test description is longer than the status alignment the
> parameter 'n' to putcharn() would lead to a signed underflow that then
> gets converted to a very large unsigned value.
> This in turn leads out-of-bound writes in memset() crashing the
> application.
> 
> The failure case of EXPECT_PTRER() used in "mmap_bad" exhibits this
> exact behavior.
> 
> Fixes: 8a27526f49f9 ("selftests/nolibc: add EXPECT_PTREQ, EXPECT_PTRNE and EXPECT_PTRER")
> Signed-off-by: Thomas Wei?schuh <linux@weissschuh.net>

Applied, thank you Thomas!
Willy