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>
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f7b53637c0
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42d5e37654
3 changed files with 61 additions and 9 deletions
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@ -155,8 +155,9 @@
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#define AUDIT_FILTER_WATCH 0x03 /* Apply rule to file system watches */
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#define AUDIT_FILTER_EXIT 0x04 /* Apply rule at syscall exit */
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#define AUDIT_FILTER_TYPE 0x05 /* Apply rule at audit_log_start */
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#define AUDIT_FILTER_FS 0x06 /* Apply rule at __audit_inode_child */
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#define AUDIT_NR_FILTERS 6
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#define AUDIT_NR_FILTERS 7
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#define AUDIT_FILTER_PREPEND 0x10 /* Prepend to front of list */
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@ -256,6 +257,7 @@
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#define AUDIT_OBJ_LEV_HIGH 23
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#define AUDIT_LOGINUID_SET 24
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#define AUDIT_SESSIONID 25 /* Session ID */
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#define AUDIT_FSTYPE 26 /* FileSystem Type */
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/* These are ONLY useful when checking
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* at syscall exit time (AUDIT_AT_EXIT). */
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@ -335,13 +337,15 @@ enum {
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#define AUDIT_FEATURE_BITMAP_EXCLUDE_EXTEND 0x00000008
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#define AUDIT_FEATURE_BITMAP_SESSIONID_FILTER 0x00000010
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#define AUDIT_FEATURE_BITMAP_LOST_RESET 0x00000020
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#define AUDIT_FEATURE_BITMAP_FILTER_FS 0x00000040
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#define AUDIT_FEATURE_BITMAP_ALL (AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT | \
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AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME | \
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AUDIT_FEATURE_BITMAP_EXECUTABLE_PATH | \
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AUDIT_FEATURE_BITMAP_EXCLUDE_EXTEND | \
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AUDIT_FEATURE_BITMAP_SESSIONID_FILTER | \
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AUDIT_FEATURE_BITMAP_LOST_RESET)
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AUDIT_FEATURE_BITMAP_LOST_RESET | \
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AUDIT_FEATURE_BITMAP_FILTER_FS)
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/* deprecated: AUDIT_VERSION_* */
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#define AUDIT_VERSION_LATEST AUDIT_FEATURE_BITMAP_ALL
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@ -56,7 +56,8 @@ struct list_head audit_filter_list[AUDIT_NR_FILTERS] = {
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LIST_HEAD_INIT(audit_filter_list[3]),
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LIST_HEAD_INIT(audit_filter_list[4]),
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LIST_HEAD_INIT(audit_filter_list[5]),
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#if AUDIT_NR_FILTERS != 6
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LIST_HEAD_INIT(audit_filter_list[6]),
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#if AUDIT_NR_FILTERS != 7
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#error Fix audit_filter_list initialiser
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#endif
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};
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@ -67,6 +68,7 @@ static struct list_head audit_rules_list[AUDIT_NR_FILTERS] = {
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LIST_HEAD_INIT(audit_rules_list[3]),
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LIST_HEAD_INIT(audit_rules_list[4]),
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LIST_HEAD_INIT(audit_rules_list[5]),
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LIST_HEAD_INIT(audit_rules_list[6]),
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};
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DEFINE_MUTEX(audit_filter_mutex);
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@ -263,6 +265,7 @@ static inline struct audit_entry *audit_to_entry_common(struct audit_rule_data *
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#endif
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case AUDIT_FILTER_USER:
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case AUDIT_FILTER_TYPE:
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case AUDIT_FILTER_FS:
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;
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}
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if (unlikely(rule->action == AUDIT_POSSIBLE)) {
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@ -338,6 +341,21 @@ static int audit_field_valid(struct audit_entry *entry, struct audit_field *f)
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entry->rule.listnr != AUDIT_FILTER_USER)
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return -EINVAL;
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break;
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case AUDIT_FSTYPE:
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if (entry->rule.listnr != AUDIT_FILTER_FS)
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return -EINVAL;
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break;
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}
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switch(entry->rule.listnr) {
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case AUDIT_FILTER_FS:
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switch(f->type) {
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case AUDIT_FSTYPE:
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case AUDIT_FILTERKEY:
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break;
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default:
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return -EINVAL;
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}
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}
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switch(f->type) {
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@ -391,6 +409,7 @@ static int audit_field_valid(struct audit_entry *entry, struct audit_field *f)
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return -EINVAL;
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/* FALL THROUGH */
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case AUDIT_ARCH:
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case AUDIT_FSTYPE:
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if (f->op != Audit_not_equal && f->op != Audit_equal)
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return -EINVAL;
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break;
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@ -910,10 +929,13 @@ static inline int audit_add_rule(struct audit_entry *entry)
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#ifdef CONFIG_AUDITSYSCALL
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int dont_count = 0;
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/* If either of these, don't count towards total */
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if (entry->rule.listnr == AUDIT_FILTER_USER ||
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entry->rule.listnr == AUDIT_FILTER_TYPE)
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/* If any of these, don't count towards total */
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switch(entry->rule.listnr) {
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case AUDIT_FILTER_USER:
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case AUDIT_FILTER_TYPE:
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case AUDIT_FILTER_FS:
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dont_count = 1;
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}
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#endif
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mutex_lock(&audit_filter_mutex);
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@ -989,10 +1011,13 @@ int audit_del_rule(struct audit_entry *entry)
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#ifdef CONFIG_AUDITSYSCALL
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int dont_count = 0;
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/* If either of these, don't count towards total */
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if (entry->rule.listnr == AUDIT_FILTER_USER ||
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entry->rule.listnr == AUDIT_FILTER_TYPE)
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/* If any of these, don't count towards total */
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switch(entry->rule.listnr) {
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case AUDIT_FILTER_USER:
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case AUDIT_FILTER_TYPE:
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case AUDIT_FILTER_FS:
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dont_count = 1;
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}
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#endif
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mutex_lock(&audit_filter_mutex);
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@ -1869,10 +1869,33 @@ void __audit_inode_child(struct inode *parent,
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struct inode *inode = d_backing_inode(dentry);
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const char *dname = dentry->d_name.name;
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struct audit_names *n, *found_parent = NULL, *found_child = NULL;
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struct audit_entry *e;
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struct list_head *list = &audit_filter_list[AUDIT_FILTER_FS];
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int i;
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if (!context->in_syscall)
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return;
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rcu_read_lock();
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if (!list_empty(list)) {
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list_for_each_entry_rcu(e, list, list) {
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for (i = 0; i < e->rule.field_count; i++) {
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struct audit_field *f = &e->rule.fields[i];
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if (f->type == AUDIT_FSTYPE) {
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if (audit_comparator(parent->i_sb->s_magic,
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f->op, f->val)) {
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if (e->rule.action == AUDIT_NEVER) {
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rcu_read_unlock();
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return;
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}
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}
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}
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}
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}
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}
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rcu_read_unlock();
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if (inode)
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handle_one(inode);
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