[PATCH] call_usermodehelper() increase reliability

[KOSAKI Motohiro]

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@xxxxxxxxxxxxxx>
CC: "Paul Menage" <menage@xxxxxxxxxx>
CC: Li Zefan <lizf@xxxxxxxxxxxxxx>
CC: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
CC: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
CC: Andi Kleen <andi@xxxxxxxxxxxxxx>

---
 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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