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Date:   Tue, 8 Nov 2022 13:05:51 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Francis Laniel <flaniel@linux.microsoft.com>
Cc:     linux-kernel@vger.kernel.org,
        Alban Crequy <alban.crequy@gmail.com>,
        Alban Crequy <albancrequy@microsoft.com>,
        Andrii Nakryiko <andrii@kernel.org>,
        Mykola Lysenko <mykolal@fb.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        Shuah Khan <shuah@kernel.org>, linux-mm@kvack.org,
        bpf@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [RFC PATCH v1 1/2] maccess: fix writing offset in case of fault
 in strncpy_from_kernel_nofault()
Message-Id: <20221108130551.85ad67b402582e3855418294@linux-foundation.org>
In-Reply-To: <20221108195211.214025-2-flaniel@linux.microsoft.com>
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        <20221108195211.214025-2-flaniel@linux.microsoft.com>
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On Tue,  8 Nov 2022 20:52:06 +0100 Francis Laniel <flaniel@linux.microsoft.com> wrote:

> From: Alban Crequy <albancrequy@microsoft.com>
> 
> If a page fault occurs while copying the first byte, this function resets one
> byte before dst.
> As a consequence, an address could be modified and leaded to kernel crashes if
> case the modified address was accessed later.
> 
> Signed-off-by: Alban Crequy <albancrequy@microsoft.com>
> Tested-by: Francis Laniel <flaniel@linux.microsoft.com>

Reviewed-by: Andrew Morton <akpm@linux-foundation.org>

Please merge via the bpf tree.

This looks potentially nasty.  Fortunately only tracing code uses it,
but I'm thinking it should have cc:stable and a Fixes:?