call_usermodehelper: simplify/fix UMH_NO_WAIT case (d47419cd) · Commits · 戴 / test

__call_usermodehelper(UMH_NO_WAIT) has 2 problems: - if kernel_thread() fails, call_usermodehelper_freeinfo() is not called. - for unknown reason UMH_NO_WAIT has UMH_WAIT_PROC logic, we spawn yet another thread which waits until the user mode application exits. Change the UMH_NO_WAIT code to use ____call_usermodehelper() instead of wait_for_helper(), and do call_usermodehelper_freeinfo() unconditionally. We can rely on CLONE_VFORK, do_fork(CLONE_VFORK) until the child exits or execs. With or without this patch UMH_NO_WAIT does not report the error if kernel_thread() fails, this is correct since the caller doesn't wait for result. Signed-off-by:

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

+4 −6

Original line number	Diff line number	Diff line
		@@ -205,9 +205,6 @@ static int wait_for_helper(void *data)
		sub_info->retval = ret;
		}

		if (sub_info->wait == UMH_NO_WAIT)
		call_usermodehelper_freeinfo(sub_info);
		else
		complete(sub_info->complete);
		return 0;
		}
		@@ -217,13 +214,13 @@ static void __call_usermodehelper(struct work_struct *work)
		{
		struct subprocess_info *sub_info =
		container_of(work, struct subprocess_info, work);
		pid_t pid;
		enum umh_wait wait = sub_info->wait;
		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 \|\| wait == UMH_NO_WAIT)
		if (wait == UMH_WAIT_PROC)
		pid = kernel_thread(wait_for_helper, sub_info,
		CLONE_FS \| CLONE_FILES \| SIGCHLD);
		else
		@@ -232,6 +229,7 @@ static void __call_usermodehelper(struct work_struct *work)

		switch (wait) {
		case UMH_NO_WAIT:
		call_usermodehelper_freeinfo(sub_info);
		break;

		case UMH_WAIT_PROC:

Admin message