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[PATCH] uml: fix hang on run_helper() failure on uml_net

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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: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Paolo 'Blaisorblade' Giarrusso 2006-04-10 22:53:37 -07:00 committed by Linus Torvalds
parent e6fb54abb8
commit b1c332c9e8
2 changed files with 8 additions and 6 deletions
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4
arch/um/drivers/net_user.c
View File

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

10
arch/um/os-Linux/helper.c
View File

@ -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){
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 {