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Date: Mon, 27 May 2019 15:38:26 +0200 From: Jann Horn <jannh@...gle.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Alexander Viro <viro@...iv.linux.org.uk>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, kernel list <linux-kernel@...r.kernel.org>, Kees Cook <keescook@...omium.org>, Nicolas Pitre <nicolas.pitre@...aro.org>, Arnd Bergmann <arnd@...db.de>, Geert Uytterhoeven <geert@...ux-m68k.org>, linux-m68k@...r.kernel.org, Russell King <linux@...linux.org.uk>, linux-arm-kernel@...ts.infradead.org Subject: Re: [PATCH] binfmt_flat: make load_flat_shared_library() work On Sat, May 25, 2019 at 11:43 PM Andrew Morton <akpm@...ux-foundation.org> wrote: > On Fri, 24 May 2019 22:18:17 +0200 Jann Horn <jannh@...gle.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@...r.kernel.org > > Fixes: 287980e49ffc ("remove lots of IS_ERR_VALUE abuses") > > Signed-off-by: Jann Horn <jannh@...gle.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.
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