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audit: filter PATH records keyed on filesystem magic

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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>
This commit is contained in:
Richard Guy Briggs
2017-08-23 07:03:39 -04:00
committed by Paul Moore
parent f7b53637c0
commit 42d5e37654
3 changed files with 61 additions and 9 deletions
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8
include/uapi/linux/audit.h
View File

@@ -155,8 +155,9 @@
#define AUDIT_FILTER_WATCH 0x03 /* Apply rule to file system watches */
#define AUDIT_FILTER_EXIT 0x04 /* Apply rule at syscall exit */
#define AUDIT_FILTER_TYPE 0x05 /* Apply rule at audit_log_start */
#define AUDIT_FILTER_FS 0x06 /* Apply rule at __audit_inode_child */
#define AUDIT_NR_FILTERS 6
#define AUDIT_NR_FILTERS 7
#define AUDIT_FILTER_PREPEND 0x10 /* Prepend to front of list */
@@ -256,6 +257,7 @@
#define AUDIT_OBJ_LEV_HIGH 23
#define AUDIT_LOGINUID_SET 24
#define AUDIT_SESSIONID 25 /* Session ID */
#define AUDIT_FSTYPE 26 /* FileSystem Type */
/* These are ONLY useful when checking
* at syscall exit time (AUDIT_AT_EXIT). */
@@ -335,13 +337,15 @@ enum {
#define AUDIT_FEATURE_BITMAP_EXCLUDE_EXTEND 0x00000008
#define AUDIT_FEATURE_BITMAP_SESSIONID_FILTER 0x00000010
#define AUDIT_FEATURE_BITMAP_LOST_RESET 0x00000020
#define AUDIT_FEATURE_BITMAP_FILTER_FS 0x00000040
#define AUDIT_FEATURE_BITMAP_ALL (AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT | \
AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME | \
AUDIT_FEATURE_BITMAP_EXECUTABLE_PATH | \
AUDIT_FEATURE_BITMAP_EXCLUDE_EXTEND | \
AUDIT_FEATURE_BITMAP_SESSIONID_FILTER | \
AUDIT_FEATURE_BITMAP_LOST_RESET)
AUDIT_FEATURE_BITMAP_LOST_RESET | \
AUDIT_FEATURE_BITMAP_FILTER_FS)
/* deprecated: AUDIT_VERSION_* */
#define AUDIT_VERSION_LATEST AUDIT_FEATURE_BITMAP_ALL