linux-kernel - Re: [PATCH] call_usermodehelper() increase reliability

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Date:	Wed, 28 May 2008 09:05:28 +0100
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
CC:	Paul Menage <menage@...gle.com>, Li Zefan <lizf@...fujitsu.com>,
	Jeremy Fitzhardinge <jeremy@...source.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] call_usermodehelper() increase reliability

KOSAKI Motohiro wrote:
> Now, call_usermodehelper_setup() uses GFP_ATOMIC.
> but it can return NULL _very_ easily.
>
> GFP_ATOMIC is needed only when we can't sleep.
> and, GFP_KERNEL is robust and better.
>
> thus, I add gfp_mask argument to call_usermodehelper_setup().
>
> So, its caller pass below,
>
> call_usermodehelper() and call_usermodehelper_keys(): 
> 	depend on 'wait' argument.
> call_usermodehelper_pipe():
> 	always GFP_KERNEL because always run under process context.
> orderly_poweroff():
> 	pass to GFP_ATOMIC because may run under interrupt context.
>
>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> CC: "Paul Menage" <menage@...gle.com>
> CC: Li Zefan <lizf@...fujitsu.com>
> CC: Jeremy Fitzhardinge <jeremy@...source.com>
> CC: Rusty Russell <rusty@...tcorp.com.au>
> CC: Andi Kleen <andi@...stfloor.org>
>   

Yes, looks good.

Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>

> ---
>  include/linux/kmod.h |   11 +++++++----
>  kernel/kmod.c        |    9 +++++----
>  kernel/sys.c         |    2 +-
>  3 files changed, 13 insertions(+), 9 deletions(-)
>
> Index: b/kernel/kmod.c
> ===================================================================
> --- a/kernel/kmod.c
> +++ b/kernel/kmod.c
> @@ -352,16 +352,17 @@ static inline void register_pm_notifier_
>   * @path: path to usermode executable
>   * @argv: arg vector for process
>   * @envp: environment for process
> + * @gfp_mask: gfp mask for memory allocation
>   *
>   * Returns either %NULL on allocation failure, or a subprocess_info
>   * structure.  This should be passed to call_usermodehelper_exec to
>   * exec the process and free the structure.
>   */
> -struct subprocess_info *call_usermodehelper_setup(char *path,
> -						  char **argv, char **envp)
> +struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
> +						  char **envp, gfp_t gfp_mask)
>  {
>  	struct subprocess_info *sub_info;
> -	sub_info = kzalloc(sizeof(struct subprocess_info),  GFP_ATOMIC);
> +	sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
>  	if (!sub_info)
>  		goto out;
>  
> @@ -494,7 +495,7 @@ int call_usermodehelper_pipe(char *path,
>  	struct subprocess_info *sub_info;
>  	int ret;
>  
> -	sub_info = call_usermodehelper_setup(path, argv, envp);
> +	sub_info = call_usermodehelper_setup(path, argv, envp, GFP_KERNEL);
>  	if (sub_info == NULL)
>  		return -ENOMEM;
>  
> Index: b/include/linux/kmod.h
> ===================================================================
> --- a/include/linux/kmod.h
> +++ b/include/linux/kmod.h
> @@ -19,6 +19,7 @@
>   *      Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
>   */
>  
> +#include <linux/gfp.h>
>  #include <linux/stddef.h>
>  #include <linux/errno.h>
>  #include <linux/compiler.h>
> @@ -40,8 +41,8 @@ struct file;
>  struct subprocess_info;
>  
>  /* Allocate a subprocess_info structure */
> -struct subprocess_info *call_usermodehelper_setup(char *path,
> -						  char **argv, char **envp);
> +struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
> +						  char **envp, gfp_t gfp_mask);
>  
>  /* Set various pieces of state into the subprocess_info structure */
>  void call_usermodehelper_setkeys(struct subprocess_info *info,
> @@ -68,8 +69,9 @@ static inline int
>  call_usermodehelper(char *path, char **argv, char **envp, enum umh_wait wait)
>  {
>  	struct subprocess_info *info;
> +	gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
>  
> -	info = call_usermodehelper_setup(path, argv, envp);
> +	info = call_usermodehelper_setup(path, argv, envp, gfp_mask);
>  	if (info == NULL)
>  		return -ENOMEM;
>  	return call_usermodehelper_exec(info, wait);
> @@ -80,8 +82,9 @@ call_usermodehelper_keys(char *path, cha
>  			 struct key *session_keyring, enum umh_wait wait)
>  {
>  	struct subprocess_info *info;
> +	gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
>  
> -	info = call_usermodehelper_setup(path, argv, envp);
> +	info = call_usermodehelper_setup(path, argv, envp, gfp_mask);
>  	if (info == NULL)
>  		return -ENOMEM;
>  
> Index: b/kernel/sys.c
> ===================================================================
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -1795,7 +1795,7 @@ int orderly_poweroff(bool force)
>  		goto out;
>  	}
>  
> -	info = call_usermodehelper_setup(argv[0], argv, envp);
> +	info = call_usermodehelper_setup(argv[0], argv, envp, GFP_ATOMIC);
>  	if (info == NULL) {
>  		argv_free(argv);
>  		goto out;
>
>
> --
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