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SubjectRe: [PATCH] binfmt_flat: make load_flat_shared_library() work
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On 27/5/19 11:38 pm, Jann Horn wrote:
> On Sat, May 25, 2019 at 11:43 PM Andrew Morton
> <akpm@linux-foundation.org> wrote:
>> On Fri, 24 May 2019 22:18:17 +0200 Jann Horn <jannh@google.com> 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 <jannh@google.com>
>>> ---
>>> 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...
>
> Maybe... but I didn't want to rip it out without having one of the
> maintainers confirm that this really isn't likely to be used anymore.

I have not used shared libraries on m68k non-mmu setups for
a very long time. At least 10 years I would think.

Regards
Greg



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