Commit 7117bc88 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

usermodehelper: don't use CLONE_VFORK for ____call_usermodehelper() 



After "kernel/kmod: fix use-after-free of the sub_infostructure"
CLONE_VFORK in __call_usermodehelper() buys nothing, we rely on on
umh_complete() in ____call_usermodehelper() anyway.

Remove it.  This also eliminates the unnecessary sleep/wakeup in the
likely case, and this allows the next change.

While at it, kill the "int wait" locals in ____call_usermodehelper() and
__call_usermodehelper(), they can safely use sub_info->wait.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ddbc22e2

kernel/kmod.c

+3 −9
Original line number Diff line number Diff line
@@ -223,7 +223,6 @@ static void umh_complete(struct subprocess_info *sub_info) 
static int ____call_usermodehelper(void *data)

{

	struct subprocess_info *sub_info = data;

	int wait = sub_info->wait & ~UMH_KILLABLE;

	struct cred *new;

	int retval;
@@ -267,7 +266,7 @@ static int ____call_usermodehelper(void *data) 
out:

	sub_info->retval = retval;

	/* wait_for_helper() will call umh_complete if UHM_WAIT_PROC. */

	if (wait != UMH_WAIT_PROC)

	if (!(sub_info->wait & UMH_WAIT_PROC))

		umh_complete(sub_info);

	if (!retval)

		return 0;
@@ -323,18 +322,13 @@ static void __call_usermodehelper(struct work_struct *work) 
{

	struct subprocess_info *sub_info =

		container_of(work, struct subprocess_info, work);

	int wait = sub_info->wait & ~UMH_KILLABLE;

	pid_t pid;



	/* CLONE_VFORK: wait until the usermode helper has execve'd

	 * successfully We need the data structures to stay around

	 * until that is done.  */

	if (wait == UMH_WAIT_PROC)

	if (sub_info->wait & UMH_WAIT_PROC)

		pid = kernel_thread(wait_for_helper, sub_info,

				    CLONE_FS | CLONE_FILES | SIGCHLD);

	else {

		pid = kernel_thread(call_helper, sub_info,

				    CLONE_VFORK | SIGCHLD);

		pid = kernel_thread(call_helper, sub_info, SIGCHLD);

		/* Worker thread stopped blocking khelper thread. */

		kmod_thread_locker = NULL;

	}