From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [PATCH] binfmt_flat: make load_flat_shared_library() work Date: Sat, 25 May 2019 14:43:04 -0700 Message-ID: <20190525144304.e2b9475a18a1f78a964c5640@linux-foundation.org> References: <20190524201817.16509-1-jannh@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190524201817.16509-1-jannh@google.com> Sender: linux-kernel-owner@vger.kernel.org To: Jann Horn Cc: Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Kees Cook , Nicolas Pitre , Arnd Bergmann , Geert Uytterhoeven , linux-m68k@vger.kernel.org, Russell King , linux-arm-kernel@lists.infradead.org List-Id: linux-m68k@vger.kernel.org On Fri, 24 May 2019 22:18:17 +0200 Jann Horn wrote: > load_flat_shared_library() is broken: It only calls load_flat_file() if > prepare_binprm() returns zero, but prepare_binprm() returns the number of > bytes read - so this only happens if the file is empty. ouch. > Instead, call into load_flat_file() if the number of bytes read is > non-negative. (Even if the number of bytes is zero - in that case, > load_flat_file() will see nullbytes and return a nice -ENOEXEC.) > > In addition, remove the code related to bprm creds and stop using > prepare_binprm() - this code is loading a library, not a main executable, > and it only actually uses the members "buf", "file" and "filename" of the > linux_binprm struct. Instead, call kernel_read() directly. > > Cc: stable@vger.kernel.org > Fixes: 287980e49ffc ("remove lots of IS_ERR_VALUE abuses") > Signed-off-by: Jann Horn > --- > I only found the bug by looking at the code, I have not verified its > existence at runtime. > Also, this patch is compile-tested only. > It would be nice if someone who works with nommu Linux could have a > look at this patch. 287980e49ffc was three years ago! Has it really been broken for all that time? If so, it seems a good source of freed disk space...