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Date: Thu, 02 Aug 2012 00:03:07 +0200
From: Richard Weinberger <richard@....at>
To: Meredydd Luff <meredydd@...atehouse.org>
CC: linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
Jeff Dike <jdike@...toit.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] [RFC] syscalls,x86: Add execveat() system call
On 01.08.2012 23:44, Meredydd Luff wrote:
> HPA is already on record calling for an execveat() which also does
> fexecve()'s job: https://lkml.org/lkml/2006/7/11/556.
> And the current glibc hack for fexecve() is already causing problems
> in the wild. Eg: https://bugzilla.redhat.com/show_bug.cgi?id=241609,
> https://lkml.org/lkml/2006/12/27/123, and as recounted at
> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043.
>
> So here's an attempt at just that:
>
> ----------------------------------------------------------------------
>
> This patch adds a new system call, execveat(2). execveat() is to
> execve() as openat() is to open(): it takes file descriptor that
> refers to a directory, and resolves the filename relative to that.
>
> In addition, if the filename is NULL, execveat() executes the file
> to which the file descriptor refers. This replicates the functionality
> of fexecve(), which is a system call in other UNIXen, but in Linux
> glibc v2.16 it's a gross hack that depends on /proc being mounted.
> That hack does not work in chrooted sandboxes, or stripped-down
> systems without /proc mounted. execveat() does.
>
> Only x86-64 and i386 ABIs are supported in this patch. User-Mode Linux
> is also supported.
>
> Signed-off-by: Meredydd Luff <meredydd@...atehouse.org>
> ---
> CREDITS | 5 +++
> arch/alpha/kernel/binfmt_loader.c | 2 +-
> arch/um/kernel/exec.c | 36 ++++++++++++++++----
> arch/x86/ia32/ia32entry.S | 1 +
> arch/x86/ia32/sys_ia32.c | 20 +++++++++++
> arch/x86/include/asm/sys_ia32.h | 3 ++
> arch/x86/kernel/entry_32.S | 17 ++++++++++
> arch/x86/kernel/entry_64.S | 15 ++++++++
> arch/x86/kernel/process.c | 27 +++++++++++++++
> arch/x86/syscalls/syscall_32.tbl | 1 +
> arch/x86/syscalls/syscall_64.tbl | 1 +
> arch/x86/um/sys_call_table_32.c | 1 +
> arch/x86/um/sys_call_table_64.c | 1 +
> fs/binfmt_elf.c | 2 +-
> fs/binfmt_elf_fdpic.c | 2 +-
> fs/binfmt_em86.c | 2 +-
> fs/binfmt_flat.c | 2 +-
> fs/binfmt_misc.c | 2 +-
> fs/binfmt_script.c | 2 +-
> fs/exec.c | 65 ++++++++++++++++++++++++++++++------
> include/asm-generic/syscalls.h | 7 ++++
> include/linux/compat.h | 2 +
> include/linux/fs.h | 2 +-
> include/linux/sched.h | 3 ++
> 24 files changed, 195 insertions(+), 26 deletions(-)
>
> diff --git a/CREDITS b/CREDITS
> index d8fe12a..859b40b 100644
> --- a/CREDITS
> +++ b/CREDITS
> @@ -2177,6 +2177,11 @@ S: Asterisk Ltd.
> S: Auckland
> S: New Zealand
>
> +N: Meredydd Luff
> +E: meredydd@...atehouse.org
> +W: http://www.senatehouse.org/
> +D: execveat() system call
> +
CREDITS is no longer used.
git log is the new CREDITS file. :-)
> N: Tuomas J. Lukka
> E: Tuomas.Lukka@...sinki.FI
> D: Original dual-monitor patches
> diff --git a/arch/alpha/kernel/binfmt_loader.c b/arch/alpha/kernel/binfmt_loader.c
> index d1f474d..7968491 100644
> --- a/arch/alpha/kernel/binfmt_loader.c
> +++ b/arch/alpha/kernel/binfmt_loader.c
> @@ -24,7 +24,7 @@ static int load_binary(struct linux_binprm *bprm, struct pt_regs *regs)
>
> loader = bprm->vma->vm_end - sizeof(void *);
>
> - file = open_exec("/sbin/loader");
> + file = open_exec(AT_FDCWD, "/sbin/loader");
> retval = PTR_ERR(file);
> if (IS_ERR(file))
> return retval;
> diff --git a/arch/um/kernel/exec.c b/arch/um/kernel/exec.c
> index 6cade93..cd7b2a9 100644
> --- a/arch/um/kernel/exec.c
> +++ b/arch/um/kernel/exec.c
> @@ -5,6 +5,7 @@
>
> #include <linux/stddef.h>
> #include <linux/module.h>
> +#include <linux/fcntl.h>
> #include <linux/fs.h>
> #include <linux/ptrace.h>
> #include <linux/sched.h>
> @@ -44,13 +45,13 @@ void start_thread(struct pt_regs *regs, unsigned long eip, unsigned long esp)
> }
> EXPORT_SYMBOL(start_thread);
>
> -static long execve1(const char *file,
> - const char __user *const __user *argv,
> - const char __user *const __user *env)
> +static long execveat1(int dfd, const char *file,
> + const char __user *const __user *argv,
> + const char __user *const __user *env)
> {
> long error;
>
> - error = do_execve(file, argv, env, ¤t->thread.regs);
> + error = do_execveat(dfd, file, argv, env, ¤t->thread.regs);
> if (error == 0) {
> task_lock(current);
> current->ptrace &= ~PT_DTRACE;
> @@ -66,7 +67,7 @@ long um_execve(const char *file, const char __user *const __user *argv, const ch
> {
> long err;
>
> - err = execve1(file, argv, env);
> + err = execveat1(AT_FDCWD, file, argv, env);
> if (!err)
> UML_LONGJMP(current->thread.exec_buf, 1);
> return err;
> @@ -80,9 +81,30 @@ long sys_execve(const char __user *file, const char __user *const __user *argv,
>
> filename = getname(file);
> error = PTR_ERR(filename);
> - if (IS_ERR(filename)) goto out;
> - error = execve1(filename, argv, env);
> + if (IS_ERR(filename))
> + goto out;
Please send this coding style fix as separate patch.
Thanks,
//richard
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