audit: filter PATH records keyed on filesystem magic
Tracefs or debugfs were causing hundreds to thousands of 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
Provide a method to ignore these large number of PATH records from
overwhelming the logs if they are not of interest. Introduce a new
filter list "AUDIT_FILTER_FS", with a new field type AUDIT_FSTYPE,
which keys off the filesystem 4-octet hexadecimal magic identifier to
filter specific filesystem PATH records.
An example rule would look like:
-a never,filesystem -F fstype=0x74726163 -F key=ignore_tracefs
-a never,filesystem -F fstype=0x64626720 -F key=ignore_debugfs
Arguably the better way to address this issue is to disable tracefs and
debugfs on boot from production systems.
See: https://github.com/linux-audit/audit-kernel/issues/16
See: https://github.com/linux-audit/audit-userspace/issues/8
Test case: https://github.com/linux-audit/audit-testsuite/issues/42
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
[PM: fixed the whitespace damage in kernel/auditsc.c]
Signed-off-by: Paul Moore <paul@paul-moore.com>
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index 0b0aa58..4a1758a 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -56,7 +56,8 @@ struct list_head audit_filter_list[AUDIT_NR_FILTERS] = {
LIST_HEAD_INIT(audit_filter_list[3]),
LIST_HEAD_INIT(audit_filter_list[4]),
LIST_HEAD_INIT(audit_filter_list[5]),
-#if AUDIT_NR_FILTERS != 6
+ LIST_HEAD_INIT(audit_filter_list[6]),
+#if AUDIT_NR_FILTERS != 7
#error Fix audit_filter_list initialiser
#endif
};
@@ -67,6 +68,7 @@ static struct list_head audit_rules_list[AUDIT_NR_FILTERS] = {
LIST_HEAD_INIT(audit_rules_list[3]),
LIST_HEAD_INIT(audit_rules_list[4]),
LIST_HEAD_INIT(audit_rules_list[5]),
+ LIST_HEAD_INIT(audit_rules_list[6]),
};
DEFINE_MUTEX(audit_filter_mutex);
@@ -263,6 +265,7 @@ static inline struct audit_entry *audit_to_entry_common(struct audit_rule_data *
#endif
case AUDIT_FILTER_USER:
case AUDIT_FILTER_TYPE:
+ case AUDIT_FILTER_FS:
;
}
if (unlikely(rule->action == AUDIT_POSSIBLE)) {
@@ -338,6 +341,21 @@ static int audit_field_valid(struct audit_entry *entry, struct audit_field *f)
entry->rule.listnr != AUDIT_FILTER_USER)
return -EINVAL;
break;
+ case AUDIT_FSTYPE:
+ if (entry->rule.listnr != AUDIT_FILTER_FS)
+ return -EINVAL;
+ break;
+ }
+
+ switch(entry->rule.listnr) {
+ case AUDIT_FILTER_FS:
+ switch(f->type) {
+ case AUDIT_FSTYPE:
+ case AUDIT_FILTERKEY:
+ break;
+ default:
+ return -EINVAL;
+ }
}
switch(f->type) {
@@ -391,6 +409,7 @@ static int audit_field_valid(struct audit_entry *entry, struct audit_field *f)
return -EINVAL;
/* FALL THROUGH */
case AUDIT_ARCH:
+ case AUDIT_FSTYPE:
if (f->op != Audit_not_equal && f->op != Audit_equal)
return -EINVAL;
break;
@@ -910,10 +929,13 @@ static inline int audit_add_rule(struct audit_entry *entry)
#ifdef CONFIG_AUDITSYSCALL
int dont_count = 0;
- /* If either of these, don't count towards total */
- if (entry->rule.listnr == AUDIT_FILTER_USER ||
- entry->rule.listnr == AUDIT_FILTER_TYPE)
+ /* If any of these, don't count towards total */
+ switch(entry->rule.listnr) {
+ case AUDIT_FILTER_USER:
+ case AUDIT_FILTER_TYPE:
+ case AUDIT_FILTER_FS:
dont_count = 1;
+ }
#endif
mutex_lock(&audit_filter_mutex);
@@ -989,10 +1011,13 @@ int audit_del_rule(struct audit_entry *entry)
#ifdef CONFIG_AUDITSYSCALL
int dont_count = 0;
- /* If either of these, don't count towards total */
- if (entry->rule.listnr == AUDIT_FILTER_USER ||
- entry->rule.listnr == AUDIT_FILTER_TYPE)
+ /* If any of these, don't count towards total */
+ switch(entry->rule.listnr) {
+ case AUDIT_FILTER_USER:
+ case AUDIT_FILTER_TYPE:
+ case AUDIT_FILTER_FS:
dont_count = 1;
+ }
#endif
mutex_lock(&audit_filter_mutex);
