linux-kernel - Re: [PATCH] selftests/nolibc: avoid buffer underrun in space printing

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Message-ID: <20230729072933.GF956@1wt.eu>
Date:   Sat, 29 Jul 2023 09:29:33 +0200
From:   Willy Tarreau <w@....eu>
To:     Thomas Weißschuh <linux@...ssschuh.net>
Cc:     Shuah Khan <shuah@...nel.org>, Zhangjin Wu <falcon@...ylab.org>,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests/nolibc: avoid buffer underrun in space printing

On Wed, Jul 26, 2023 at 08:08:13AM +0200, Thomas Weißschuh 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 Weißschuh <linux@...ssschuh.net>

Applied, thank you Thomas!
Willy