core_pattern: allow passing of arguments to user mode helper when core_pattern is a pipe

A rewrite of my previous post for this enhancement.  It uses jeremy's
split_argv/free_argv library functions to translate core_pattern into an argv
array to be passed to the user mode helper process.  It also adds a
translation to format_corename such that the origional value of RLIMIT_CORE
can be passed to userspace as an argument.
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Cc: <martin.pitt@ubuntu.com>
Cc: <wwoods@redhat.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/exec.c

@@ -29,6 +29,7 @@
 #include <linux/stat.h>
 #include <linux/fcntl.h>
 #include <linux/smp_lock.h>
+#include <linux/string.h>
 #include <linux/init.h>
 #include <linux/pagemap.h>
 #include <linux/highmem.h>
@@ -1514,6 +1515,14 @@ static int format_corename(char *corename, const char *pattern, long signr)
 					goto out;
 				out_ptr += rc;
 				break;
+			/* core limit size */
+			case 'c':
+				rc = snprintf(out_ptr, out_end - out_ptr,
+					      "%lu", current->signal->rlim[RLIMIT_CORE].rlim_cur);
+				if (rc > out_end - out_ptr)
+					goto out;
+				out_ptr += rc;
+				break;
 			default:
 				break;
 			}
@@ -1698,6 +1707,9 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
 	int flag = 0;
 	int ispipe = 0;
 	unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
+	char **helper_argv = NULL;
+	int helper_argc = 0;
+	char *delimit;
 
 	audit_core_dumps(signr);
 
@@ -1746,14 +1758,18 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
 	 * at which point file size limits and permissions will be imposed
 	 * as it does with any other process
 	 */
-	if ((!ispipe) &&
-	   (core_limit < binfmt->min_coredump))
+	if ((!ispipe) && (core_limit < binfmt->min_coredump))
 		goto fail_unlock;
 
  	if (ispipe) {
 		core_limit = RLIM_INFINITY;
+		helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc);
+		/* Terminate the string before the first option */
+		delimit = strchr(corename, ' ');
+		if (delimit)
+			*delimit = '\0';
 		/* SIGPIPE can happen, but it's just never processed */
- 		if(call_usermodehelper_pipe(corename+1, NULL, NULL, &file)) {
+ 		if(call_usermodehelper_pipe(corename+1, helper_argv, NULL, &file)) {
  			printk(KERN_INFO "Core dump to %s pipe failed\n",
 			       corename);
  			goto fail_unlock;
@@ -1788,6 +1804,9 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
 close_fail:
 	filp_close(file, NULL);
 fail_unlock:
+	if (helper_argv)
+		argv_free(helper_argv);
+
 	current->fsuid = fsuid;
 	complete_all(&mm->core_done);
 fail: