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Commit b1c332c9 authored by Paolo 'Blaisorblade' Giarrusso's avatar Paolo 'Blaisorblade' Giarrusso Committed by Linus Torvalds
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[PATCH] uml: fix hang on run_helper() failure on uml_net 



Fix an hang on a pipe when run_helper() fails when called by change_tramp()
(i.e.  when calling uml_net) - reproduced the bug and verified this fixes it.

Signed-off-by: default avatarPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e6fb54ab

arch/um/drivers/net_user.c

+3 −1
Original line number Diff line number Diff line
@@ -182,7 +182,9 @@ static int change_tramp(char **argv, char *output, int output_len) 
	pe_data.stdout = fds[1];

	pid = run_helper(change_pre_exec, &pe_data, argv, NULL);



	if (pid > 0)	/* Avoid hang as we won't get data in failure case. */

		read_output(fds[0], output, output_len);



	os_close_file(fds[0]);

	os_close_file(fds[1]);

arch/um/os-Linux/helper.c

+5 −5
Original line number Diff line number Diff line
@@ -43,7 +43,7 @@ static int helper_child(void *arg) 
		(*data->pre_exec)(data->pre_data);

	execvp(argv[0], argv);

	errval = errno;

	printk("execvp of '%s' failed - errno = %d\n", argv[0], errno);

	printk("helper_child - execve of '%s' failed - errno = %d\n", argv[0], errno);

	os_write_file(data->fd, &errval, sizeof(errval));

	kill(os_getpid(), SIGKILL);

	return(0);
@@ -92,15 +92,15 @@ int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv, 
	close(fds[1]);

	fds[1] = -1;



	/*Read the errno value from the child.*/

	/* Read the errno value from the child, if the exec failed, or get 0 if

	 * the exec succeeded because the pipe fd was set as close-on-exec. */

	n = os_read_file(fds[0], &ret, sizeof(ret));

	if (n < 0) {

		printk("run_helper : read on pipe failed, ret = %d\n", -n);

		ret = n;

		kill(pid, SIGKILL);

		CATCH_EINTR(waitpid(pid, NULL, 0));

	}

	else if(n != 0){

	} else if(n != 0){

		CATCH_EINTR(n = waitpid(pid, NULL, 0));

		ret = -errno;

	} else {