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Message-ID: <20130309202134.GB16399@redhat.com>
Date: Sat, 9 Mar 2013 21:21:34 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Lucas De Marchi <lucas.demarchi@...fusion.mobi>
Cc: lucas.de.marchi@...il.com, David Howells <dhowells@...hat.com>,
James Morris <james.l.morris@...cle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/7] usermodehelper: Export _exec() and _setup()
functions
On 03/08, Lucas De Marchi wrote:
>
> call_usermodehelper_setup() + call_usermodehelper_exec() need to be
> called instead of call_usermodehelper_fns() when the cleanup function
> needs to be called even when an ENOMEM error occurs. In this case using
> call_usermodehelper_fns() the user can't distinguish if the cleanup
> function was called or not.
>
> Signed-off-by: Lucas De Marchi <lucas.demarchi@...fusion.mobi>
Reviewed-by: Oleg Nesterov <oleg@...hat.com>
> ---
> include/linux/kmod.h | 8 ++++++++
> kernel/kmod.c | 56 +++++++++++++++++++++-------------------------------
> 2 files changed, 31 insertions(+), 33 deletions(-)
>
> diff --git a/include/linux/kmod.h b/include/linux/kmod.h
> index 5398d58..7eebcf5 100644
> --- a/include/linux/kmod.h
> +++ b/include/linux/kmod.h
> @@ -71,6 +71,14 @@ call_usermodehelper_fns(char *path, char **argv, char **envp, int wait,
> int (*init)(struct subprocess_info *info, struct cred *new),
> void (*cleanup)(struct subprocess_info *), void *data);
>
> +extern struct subprocess_info *
> +call_usermodehelper_setup(char *path, char **argv, char **envp, gfp_t gfp_mask,
> + int (*init)(struct subprocess_info *info, struct cred *new),
> + void (*cleanup)(struct subprocess_info *), void *data);
> +
> +extern int
> +call_usermodehelper_exec(struct subprocess_info *info, int wait);
> +
> static inline int
> call_usermodehelper(char *path, char **argv, char **envp, int wait)
> {
> diff --git a/kernel/kmod.c b/kernel/kmod.c
> index 56dd349..b39f240 100644
> --- a/kernel/kmod.c
> +++ b/kernel/kmod.c
> @@ -502,14 +502,28 @@ static void helper_unlock(void)
> * @argv: arg vector for process
> * @envp: environment for process
> * @gfp_mask: gfp mask for memory allocation
> + * @cleanup: a cleanup function
> + * @init: an init function
> + * @data: arbitrary context sensitive data
> *
> * 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.
> + *
> + * The init function is used to customize the helper process prior to
> + * exec. A non-zero return code causes the process to error out, exit,
> + * and return the failure to the calling process
> + *
> + * The cleanup function is just before ethe subprocess_info is about to
> + * be freed. This can be used for freeing the argv and envp. The
> + * Function must be runnable in either a process context or the
> + * context in which call_usermodehelper_exec is called.
> */
> -static
> struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
> - char **envp, gfp_t gfp_mask)
> + char **envp, gfp_t gfp_mask,
> + int (*init)(struct subprocess_info *info, struct cred *new),
> + void (*cleanup)(struct subprocess_info *info),
> + void *data)
> {
> struct subprocess_info *sub_info;
> sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
> @@ -520,38 +534,15 @@ struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
> sub_info->path = path;
> sub_info->argv = argv;
> sub_info->envp = envp;
> +
> + sub_info->cleanup = cleanup;
> + sub_info->init = init;
> + sub_info->data = data;
> out:
> return sub_info;
> }
>
> /**
> - * call_usermodehelper_setfns - set a cleanup/init function
> - * @info: a subprocess_info returned by call_usermodehelper_setup
> - * @cleanup: a cleanup function
> - * @init: an init function
> - * @data: arbitrary context sensitive data
> - *
> - * The init function is used to customize the helper process prior to
> - * exec. A non-zero return code causes the process to error out, exit,
> - * and return the failure to the calling process
> - *
> - * The cleanup function is just before ethe subprocess_info is about to
> - * be freed. This can be used for freeing the argv and envp. The
> - * Function must be runnable in either a process context or the
> - * context in which call_usermodehelper_exec is called.
> - */
> -static
> -void call_usermodehelper_setfns(struct subprocess_info *info,
> - int (*init)(struct subprocess_info *info, struct cred *new),
> - void (*cleanup)(struct subprocess_info *info),
> - void *data)
> -{
> - info->cleanup = cleanup;
> - info->init = init;
> - info->data = data;
> -}
> -
> -/**
> * call_usermodehelper_exec - start a usermode application
> * @sub_info: information about the subprocessa
> * @wait: wait for the application to finish and return status.
> @@ -563,7 +554,6 @@ void call_usermodehelper_setfns(struct subprocess_info *info,
> * asynchronously if wait is not set, and runs as a child of keventd.
> * (ie. it runs with full root capabilities).
> */
> -static
> int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
> {
> DECLARE_COMPLETION_ONSTACK(done);
> @@ -615,6 +605,7 @@ unlock:
> helper_unlock();
> return retval;
> }
> +EXPORT_SYMBOL(call_usermodehelper_exec);
>
> /*
> * call_usermodehelper_fns() will not run the caller-provided cleanup function
> @@ -630,13 +621,12 @@ int call_usermodehelper_fns(
> struct subprocess_info *info;
> gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
>
> - info = call_usermodehelper_setup(path, argv, envp, gfp_mask);
> + info = call_usermodehelper_setup(path, argv, envp, gfp_mask,
> + init, cleanup, data);
>
> if (info == NULL)
> return -ENOMEM;
>
> - call_usermodehelper_setfns(info, init, cleanup, data);
> -
> return call_usermodehelper_exec(info, wait);
> }
> EXPORT_SYMBOL(call_usermodehelper_fns);
> --
> 1.8.1.5
>
--
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