[PATCH ALT1] audit: ignore tracefs and debugfs on inode child

[Richard Guy Briggs]

Tracefs or debugfs were causing hundreds to thousands of null PATH records to
be associated with the init_module and finit_module SYSCALL records on a few
modules when the following rule was in place for startup:
	-a always,exit -F arch=x86_64 -S init_module -F key=mod-load

In __audit_inode_child, return immedialy upon detecting TRACEFS and DEBUGFS
(and potentially other filesystems identified, via dentry->d_sb->s_magic).

See https://github.com/linux-audit/audit-kernel/issues/8
Test case: https://github.com/linux-audit/audit-testsuite/issues/42

Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
---
 kernel/auditsc.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 4db32e8..6050441 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1868,6 +1868,11 @@ void __audit_inode_child(struct inode *parent,
 
 	if (!context->in_syscall)
 		return;
+	switch (parent->i_sb->s_magic) {
+	case TRACEFS_MAGIC:
+	case DEBUGFS_MAGIC:
+		return;
+	}
 
 	if (inode)
 		handle_one(inode);
-- 
1.7.1