[PATCH ghak99 v1] audit: print empty EXECVE args

[Richard Guy Briggs]

Empty executable arguments were being skipped when printing out the list
of arguments in an EXECVE record, making it appear they were somehow
lost.  Include empty arguments as an itemized empty string.

Reproducer:
	autrace /bin/ls "" "/etc"
	ausearch --start recent -m execve -i | grep EXECVE
	type=EXECVE msg=audit(10/03/2018 13:04:03.208:1391) : argc=3 a0=/bin/ls a2=/etc

With fix:
	type=EXECVE msg=audit(10/03/2018 21:51:38.290:194) : argc=3 a0=/bin/ls a1= a2=/etc
	type=EXECVE msg=audit(1538617898.290:194): argc=3 a0="/bin/ls" a1="" a2="/etc"

Passes audit-testsuite
Based on: v4.19-rc2 (audit/next)
See: https://github.com/linux-audit/audit-kernel/issues/99
Signed-off-by: Richard Guy Briggs <rgb at redhat.com>
---
 kernel/auditsc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index b2d1f04..1513873 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1107,7 +1107,7 @@ static void audit_log_execve_info(struct audit_context *context,
 		}
 
 		/* write as much as we can to the audit log */
-		if (len_buf > 0) {
+		if (len_buf >= 0) {
 			/* NOTE: some magic numbers here - basically if we
 			 *       can't fit a reasonable amount of data into the
 			 *       existing audit buffer, flush it and start with
-- 
1.8.3.1