On Fri, 24 May 2019 22:18:17 +0200 Jann Horn <jannh@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx
Fixes: 287980e49ffc ("remove lots of IS_ERR_VALUE abuses")
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
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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...
