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Message-ID: <CALCETrWbj=BTDyKqtbSKteANj3J3UFZnrvWv9DMosCoEZaSoeA@mail.gmail.com>
Date: Wed, 22 Oct 2014 11:44:29 -0700
From: Andy Lutomirski <luto@...capital.net>
To: David Drysdale <drysdale@...gle.com>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>,
Alexander Viro <viro@...iv.linux.org.uk>,
Meredydd Luff <meredydd@...atehouse.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Kees Cook <keescook@...omium.org>,
Arnd Bergmann <arnd@...db.de>, X86 ML <x86@...nel.org>,
linux-arch <linux-arch@...r.kernel.org>,
Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCHv5 1/3] syscalls,x86: implement execveat() system call
On Wed, Oct 22, 2014 at 4:44 AM, David Drysdale <drysdale@...gle.com> wrote:
> Add a new system execveat(2) syscall. execveat() is to execve() as
> openat() is to open(): it takes a file descriptor that refers to a
> directory, and resolves the filename relative to that.
>
> bprm->file = file;
> - bprm->filename = bprm->interp = filename->name;
> + if (fd == AT_FDCWD || filename->name[0] == '/') {
> + bprm->filename = filename->name;
> + } else {
> + /*
> + * Build a pathname that reflects how we got to the file,
> + * either "/dev/fd/<fd>" (for an empty filename) or
> + * "/dev/fd/<fd>/<filename>".
> + */
> + pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY);
> + if (!pathbuf) {
> + retval = -ENOMEM;
> + goto out_unmark;
> + }
> + bprm->filename = pathbuf;
> + if (filename->name[0] == '\0')
> + sprintf(pathbuf, "/dev/fd/%d", fd);
If the fd is O_CLOEXEC, then this will result in a confused child
process. Should we fail exec attempts like that for non-static
programs? (E.g. set filename to "" or something and fix up the binfmt
drivers to handle that?)
> + else
> + snprintf(pathbuf, PATH_MAX,
> + "/dev/fd/%d/%s", fd, filename->name);
Does this need to handle the case where the result exceeds PATH_MAX?
--Andy
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