usermodehelper: don't use CLONE_VFORK for ____call_usermodehelper() (7117bc88) · Commits · 戴 / test

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:

Oleg Nesterov <oleg@redhat.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

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;
		}

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