Re: [RFC][v8][PATCH 7/10]: Check invalid clone flags

[Oren Laadan]

Sukadev Bhattiprolu wrote:
> 
> Subject: [RFC][v8][PATCH 7/10]: Check invalid clone flags
> 
> As pointed out by Oren Laadan, we want to ensure that unused bits in the
> clone-flags remain unused and available for future. To ensure this, define
> a mask of clone-flags and check the flags in the clone() system calls.
> 
> Changelog[v8]:
> 	- New patch in set
> 
> Signed-off-by: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx>
> 
> ---
>  include/linux/sched.h |   10 ++++++++++
>  kernel/fork.c         |    3 +++
>  2 files changed, 13 insertions(+)
> 
> Index: linux-2.6/include/linux/sched.h
> ===================================================================
> --- linux-2.6.orig/include/linux/sched.h	2009-10-02 18:53:55.000000000 -0700
> +++ linux-2.6/include/linux/sched.h	2009-10-02 19:58:21.000000000 -0700
> @@ -29,6 +29,16 @@
>  #define CLONE_NEWNET		0x40000000	/* New network namespace */
>  #define CLONE_IO		0x80000000	/* Clone io context */
>  
> +#define VALID_CLONE_FLAGS	(CSIGNAL | CLONE_VM | CLONE_FS | CLONE_FILES |\
> +				 CLONE_SIGHAND | CLONE_PTRACE | CLONE_VFORK  |\
> +				 CLONE_PARENT | CLONE_THREAD | CLONE_NEWNS   |\
> +				 CLONE_SYSVSEM | CLONE_SETTLS                |\
> +				 CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID  |\
> +				 CLONE_DETACHED | CLONE_UNTRACED             |\
> +				 CLONE_CHILD_SETTID | CLONE_STOPPED          |\
> +				 CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWUSER |\
> +				 CLONE_NEWPID | CLONE_NEWNET| CLONE_IO)
> +
>  /*
>   * Scheduling policies
>   */
> Index: linux-2.6/kernel/fork.c
> ===================================================================
> --- linux-2.6.orig/kernel/fork.c	2009-10-02 19:00:08.000000000 -0700
> +++ linux-2.6/kernel/fork.c	2009-10-02 19:57:36.000000000 -0700
> @@ -942,6 +942,9 @@ static struct task_struct *copy_process(
>  	struct task_struct *p;
>  	int cgroup_callbacks_done = 0;
>  

We can safely apply these tests to clone3(), because it is a new syscall.

However, I don't know if applying it to clone() can break existing
application that may already be (incorrectly) using invalid flags ?

Oren.

> +	if (clone_flags & ~VALID_CLONE_FLAGS)
> +		return ERR_PTR(-EINVAL);
> +
>  	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
>  		return ERR_PTR(-EINVAL);
>  
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