[PATCH 4/3] Audit: add argc and len fields for split records

[Eric Paris <eparis@redhat.com>]

To make it possible for userspace tools to verify that all of the args
were successfully logged add 2 new pieces of information to the execve
audit messages:

1) All messages now start with argc=%d before the logging of a0.  
2) When a single large argument is split into multiple records the first
of those records will now include a lenX=%d stating the number of bytes
in the original aX argument.

example:

record1: argc=2 a0=test_file
record2: len1=12k a1[0]=first 7.5k chunk of a1 argument
record3: a1[1]=remainder of a1 argument

Signed-off-by: Eric Paris <eparis@redhat.com>

 kernel/auditsc.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index b411737..f8ac79b 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -836,6 +836,8 @@ static void audit_log_execve_info(struct audit_context *context,
 
 	p = (const char __user *)axi->mm->arg_start;
 
+	audit_log_format(*ab, "argc=%d ", axi->argc);
+
 	for (i = 0; i < axi->argc; i++, p += len) {
 		char tmp_buf[12];
 		/* how many digits are in i? */
@@ -888,6 +890,9 @@ static void audit_log_execve_info(struct audit_context *context,
 					kfree(buf);
 					return;
 				}
+				if (j == 0)
+					audit_log_format(*ab, "len%d=%ld ", i,
+							 len + tmplen);
 				audit_log_format(*ab, "a%d[%d]=", i, j);
 				audit_log_untrustedstring(*ab, buf);
 				audit_log_format(*ab, "\n");