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From:   Alexander Potapenko <glider@google.com>
Date:   Wed, 4 Mar 2020 15:36:18 +0100
Message-ID: <CAG_fn=WvVp7Nxm5E+1dYs4guMYUV8D1XZEt_AZFF6rAQEbbAeg@mail.gmail.com>
Subject: Re: KMSAN: uninit-value in simple_attr_read
To:     syzbot <syzbot+fcab69d1ada3e8d6f06b@syzkaller.appspotmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>
Cc:     linux-fsdevel@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Al Viro <viro@zeniv.linux.org.uk>
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Hi Greg, Rafael, Arnd,

> This report says it's uninit in strlen, but there's actually an
> information leak later on that lets the user read arbitrary data past
> the non-terminated attr->get_buf.

The attached PoC demonstrates the problem.
I am not sure how bad is that, given that /sys/kernel/debug is usually
accessible only to the root, and simple attribute files don't seem to
be used anywhere else.

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