[PATCH v3 0/3] dm: audit event logging

[PATCH v3 0/3] dm: audit event logging

[Michael Weiß]

dm integrity and also stacked dm crypt devices track integrity
violations internally. Thus, integrity violations could be polled
from user space, e.g., by 'integritysetup status'.

From an auditing perspective, we only could see that there were
a number of integrity violations, but not when and where the
violation exactly was taking place. The current error log to
the kernel ring buffer, contains those information, time stamp and
sector on device. However, for auditing the audit subsystem provides
a separate logging mechanism which meets certain criteria for secure
audit logging.

With this small series we make use of the kernel audit framework
and extend the dm driver to log audit events in case of such
integrity violations. Further, we also log construction and
destruction of the device mappings.

We focus on dm-integrity and stacked dm-crypt devices for now.
However, the helper functions to log audit messages should be
applicable to dm-verity too.

The first patch introduce generic audit wrapper functions.
The second patch makes use of the audit wrapper functions in the
dm-integrity.c.
The third patch uses the wrapper functions in dm-crypt.c.

The audit logs look like this if executing the following simple test:

# dd if=/dev/zero of=test.img bs=1M count=1024
# losetup -f test.img
# integritysetup -vD format --integrity sha256 -t 32 /dev/loop0
# integritysetup open -D /dev/loop0 --integrity sha256 integritytest
# integritysetup status integritytest
# integritysetup close integritytest
# integritysetup open -D /dev/loop0 --integrity sha256 integritytest
# integritysetup status integritytest
# dd if=/dev/urandom of=/dev/loop0 bs=512 count=1 seek=100000
# dd if=/dev/mapper/integritytest of=/dev/null

-------------------------
audit.log from auditd

type=UNKNOWN[1336] msg=audit(1630425039.363:184): module=integrity
op=ctr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
exe="/sbin/integritysetup" subj==unconfined dev=254:3
error_msg='success' res=1
type=UNKNOWN[1336] msg=audit(1630425039.471:185): module=integrity
op=dtr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
exe="/sbin/integritysetup" subj==unconfined dev=254:3
error_msg='success' res=1
type=UNKNOWN[1336] msg=audit(1630425039.611:186): module=integrity
op=ctr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
exe="/sbin/integritysetup" subj==unconfined dev=254:3
error_msg='success' res=1
type=UNKNOWN[1336] msg=audit(1630425054.475:187): module=integrity
op=dtr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
exe="/sbin/integritysetup" subj==unconfined dev=254:3
error_msg='success' res=1

type=UNKNOWN[1336] msg=audit(1630425073.171:191): module=integrity
op=ctr ppid=3807 pid=3883 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
exe="/sbin/integritysetup" subj==unconfined dev=254:3
error_msg='success' res=1

type=UNKNOWN[1336] msg=audit(1630425087.239:192): module=integrity
op=dtr ppid=3807 pid=3902 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
exe="/sbin/integritysetup" subj==unconfined dev=254:3
error_msg='success' res=1

type=UNKNOWN[1336] msg=audit(1630425093.755:193): module=integrity
op=ctr ppid=3807 pid=3906 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
exe="/sbin/integritysetup" subj==unconfined dev=254:3
error_msg='success' res=1

type=UNKNOWN[1337] msg=audit(1630425112.119:194): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:195): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:196): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:197): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:198): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:199): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:200): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:201): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:202): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:203): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0

v3 Changes:
- Use of two audit event types AUDIT_DM_EVENT und AUDIT_DM_CTRL
- Additionally use audit_log_task_info in case of AUDIT_DM_CTRL messages
- Provide consistent fields per message type as suggested by Paul
- Added sample events to commit message of [1/3] as suggested by Paul
- Rebased on v5.14


v2 Changes:
- Fixed compile errors if CONFIG_DM_AUDIT is not set
- Fixed formatting and typos as suggested by Casey

Michael Weiß (3):
  dm: introduce audit event module for device mapper
  dm integrity: log audit events for dm-integrity target
  dm crypt: log aead integrity violations to audit subsystem

 drivers/md/Kconfig         | 10 +++++
 drivers/md/Makefile        |  4 ++
 drivers/md/dm-audit.c      | 79 ++++++++++++++++++++++++++++++++++++++
 drivers/md/dm-audit.h      | 62 ++++++++++++++++++++++++++++++
 drivers/md/dm-crypt.c      | 22 +++++++++--
 drivers/md/dm-integrity.c  | 25 ++++++++++--
 include/uapi/linux/audit.h |  2 +
 7 files changed, 196 insertions(+), 8 deletions(-)
 create mode 100644 drivers/md/dm-audit.c
 create mode 100644 drivers/md/dm-audit.h

-- 
2.20.1

[PATCH v3 1/3] dm: introduce audit event module for device mapper

[Michael Weiß]

To be able to send auditing events to user space, we introduce a
generic dm-audit module. It provides helper functions to emit audit
events through the kernel audit subsystem. We claim the
AUDIT_DM_CTRL type=1336 and AUDIT_DM_EVENT type=1337 out of the
audit event messages range in the corresponding userspace api in
'include/uapi/linux/audit.h' for those events.

AUDIT_DM_CTRL is used to provide information about creation and
destruction of device mapper targets which are triggered by user space
admin control actions.
AUDIT_DM_EVENT is used to provide information about actual errors
during operation of the mapped device, showing e.g. integrity
violations in audit log.

Following commits to device mapper targets actually will make use of
this to emit those events in relevant cases.

The audit logs look like this if executing the following simple test:

 # dd if=/dev/zero of=test.img bs=1M count=1024
 # losetup -f test.img
 # integritysetup -vD format --integrity sha256 -t 32 /dev/loop0
 # integritysetup open -D /dev/loop0 --integrity sha256 integritytest
 # integritysetup status integritytest
 # integritysetup close integritytest
 # integritysetup open -D /dev/loop0 --integrity sha256 integritytest
 # integritysetup status integritytest
 # dd if=/dev/urandom of=/dev/loop0 bs=512 count=1 seek=100000
 # dd if=/dev/mapper/integritytest of=/dev/null

-------------------------
audit.log from auditd

type=UNKNOWN[1336] msg=audit(1630425039.363:184): module=integrity
op=ctr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
exe="/sbin/integritysetup" subj==unconfined dev=254:3
error_msg='success' res=1
type=UNKNOWN[1336] msg=audit(1630425039.471:185): module=integrity
op=dtr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
exe="/sbin/integritysetup" subj==unconfined dev=254:3
error_msg='success' res=1
type=UNKNOWN[1336] msg=audit(1630425039.611:186): module=integrity
op=ctr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
exe="/sbin/integritysetup" subj==unconfined dev=254:3
error_msg='success' res=1
type=UNKNOWN[1336] msg=audit(1630425054.475:187): module=integrity
op=dtr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
exe="/sbin/integritysetup" subj==unconfined dev=254:3
error_msg='success' res=1

type=UNKNOWN[1336] msg=audit(1630425073.171:191): module=integrity
op=ctr ppid=3807 pid=3883 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
exe="/sbin/integritysetup" subj==unconfined dev=254:3
error_msg='success' res=1

type=UNKNOWN[1336] msg=audit(1630425087.239:192): module=integrity
op=dtr ppid=3807 pid=3902 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
exe="/sbin/integritysetup" subj==unconfined dev=254:3
error_msg='success' res=1

type=UNKNOWN[1336] msg=audit(1630425093.755:193): module=integrity
op=ctr ppid=3807 pid=3906 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
exe="/sbin/integritysetup" subj==unconfined dev=254:3
error_msg='success' res=1

type=UNKNOWN[1337] msg=audit(1630425112.119:194): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:195): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:196): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:197): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:198): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:199): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:200): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:201): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:202): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0
type=UNKNOWN[1337] msg=audit(1630425112.119:203): module=integrity
op=integrity-checksum dev=254:3 sector 77480 res=0

Signed-off-by: Michael Weiß <michael.weiss@aisec.fraunhofer.de>
---
 drivers/md/Kconfig         | 10 +++++
 drivers/md/Makefile        |  4 ++
 drivers/md/dm-audit.c      | 79 ++++++++++++++++++++++++++++++++++++++
 drivers/md/dm-audit.h      | 62 ++++++++++++++++++++++++++++++
 include/uapi/linux/audit.h |  2 +
 5 files changed, 157 insertions(+)
 create mode 100644 drivers/md/dm-audit.c
 create mode 100644 drivers/md/dm-audit.h

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 0602e82a9516..48adbec12148 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -608,6 +608,7 @@ config DM_INTEGRITY
 	select CRYPTO
 	select CRYPTO_SKCIPHER
 	select ASYNC_XOR
+	select DM_AUDIT if AUDIT
 	help
 	  This device-mapper target emulates a block device that has
 	  additional per-sector tags that can be used for storing
@@ -640,4 +641,13 @@ config DM_ZONED
 
 	  If unsure, say N.
 
+config DM_AUDIT
+	bool "DM audit events"
+	depends on AUDIT
+	help
+	  Generate audit events for device-mapper.
+
+	  Enables audit logging of several security relevant events in the
+	  particular device-mapper targets, especially the integrity target.
+
 endif # MD
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index a74aaf8b1445..2f83d649500d 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -103,3 +103,7 @@ endif
 ifeq ($(CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG),y)
 dm-verity-objs			+= dm-verity-verify-sig.o
 endif
+
+ifeq ($(CONFIG_DM_AUDIT),y)
+dm-mod-objs			+= dm-audit.o
+endif
diff --git a/drivers/md/dm-audit.c b/drivers/md/dm-audit.c
new file mode 100644
index 000000000000..761ecfdcd49a
--- /dev/null
+++ b/drivers/md/dm-audit.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Creating audit records for mapped devices.
+ *
+ * Copyright (C) 2021 Fraunhofer AISEC. All rights reserved.
+ *
+ * Authors: Michael Weiß <michael.weiss@aisec.fraunhofer.de>
+ */
+
+#include <linux/audit.h>
+#include <linux/module.h>
+#include <linux/device-mapper.h>
+#include <linux/bio.h>
+#include <linux/blkdev.h>
+
+#include "dm-audit.h"
+#include "dm-core.h"
+
+static struct audit_buffer *dm_audit_log_start(int audit_type,
+					       const char *dm_msg_prefix,
+					       const char *op)
+{
+	struct audit_buffer *ab;
+
+	if (audit_enabled == AUDIT_OFF)
+		return NULL;
+
+	ab = audit_log_start(audit_context(), GFP_KERNEL, audit_type);
+	if (unlikely(!ab))
+		return NULL;
+
+	audit_log_format(ab, "module=%s op=%s", dm_msg_prefix, op);
+	return ab;
+}
+
+void dm_audit_log_ti(int audit_type, const char *dm_msg_prefix, const char *op,
+		     struct dm_target *ti, int result)
+{
+	struct audit_buffer *ab;
+	struct mapped_device *md = dm_table_get_md(ti->table);
+	int dev_major = dm_disk(md)->major;
+	int dev_minor = dm_disk(md)->first_minor;
+
+	ab = dm_audit_log_start(audit_type, dm_msg_prefix, op);
+	if (unlikely(!ab))
+		return;
+
+	switch (audit_type) {
+	case AUDIT_DM_CTRL:
+		audit_log_task_info(ab);
+		audit_log_format(ab, " dev=%d:%d error_msg='%s'", dev_major,
+				 dev_minor, !result ? ti->error : "success");
+		break;
+	case AUDIT_DM_EVENT:
+		audit_log_format(ab, " dev=%d:%d sector=?", dev_major,
+				 dev_minor);
+		break;
+	}
+	audit_log_format(ab, " res=%d", result);
+	audit_log_end(ab);
+}
+EXPORT_SYMBOL_GPL(dm_audit_log_ti);
+
+void dm_audit_log_bio(const char *dm_msg_prefix, const char *op,
+		      struct bio *bio, sector_t sector, int result)
+{
+	struct audit_buffer *ab;
+	int dev_major = MAJOR(bio->bi_bdev->bd_dev);
+	int dev_minor = MINOR(bio->bi_bdev->bd_dev);
+
+	ab = dm_audit_log_start(AUDIT_DM_EVENT, dm_msg_prefix, op);
+	if (unlikely(!ab))
+		return;
+
+	audit_log_format(ab, " dev=%d:%d sector %llu res=%d",
+			 dev_major, dev_minor, sector, result);
+	audit_log_end(ab);
+}
+EXPORT_SYMBOL_GPL(dm_audit_log_bio);
diff --git a/drivers/md/dm-audit.h b/drivers/md/dm-audit.h
new file mode 100644
index 000000000000..4e3fe8aab920
--- /dev/null
+++ b/drivers/md/dm-audit.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Creating audit records for mapped devices.
+ *
+ * Copyright (C) 2021 Fraunhofer AISEC. All rights reserved.
+ *
+ * Authors: Michael Weiß <michael.weiss@aisec.fraunhofer.de>
+ */
+
+#ifndef DM_AUDIT_H
+#define DM_AUDIT_H
+
+#include <linux/device-mapper.h>
+#include <linux/audit.h>
+
+#ifdef CONFIG_DM_AUDIT
+void dm_audit_log_bio(const char *dm_msg_prefix, const char *op,
+		      struct bio *bio, sector_t sector, int result);
+
+void dm_audit_log_ti(int audit_type, const char *dm_msg_prefix, const char *op,
+		     struct dm_target *ti, int result);
+
+static inline void dm_audit_log_ctr(const char *dm_msg_prefix,
+				    struct dm_target *ti, int result)
+{
+	dm_audit_log_ti(AUDIT_DM_CTRL, dm_msg_prefix, "ctr", ti, result);
+}
+
+static inline void dm_audit_log_dtr(const char *dm_msg_prefix,
+				    struct dm_target *ti, int result)
+{
+	dm_audit_log_ti(AUDIT_DM_CTRL, dm_msg_prefix, "dtr", ti, result);
+}
+
+static inline void dm_audit_log_target(const char *dm_msg_prefix, const char *op,
+				       struct dm_target *ti, int result)
+{
+	dm_audit_log_ti(AUDIT_DM_EVENT, dm_msg_prefix, op, ti, result);
+}
+#else
+static inline void dm_audit_log_bio(const char *dm_msg_prefix, const char *op,
+				    struct bio *bio, sector_t sector,
+				    int result)
+{
+}
+static inline void dm_audit_log_target(const char *dm_msg_prefix,
+				       const char *op, struct dm_target *ti,
+				       int result)
+{
+}
+static inline void dm_audit_log_ctr(const char *dm_msg_prefix,
+				    struct dm_target *ti, int result)
+{
+}
+
+static inline void dm_audit_log_dtr(const char *dm_msg_prefix,
+				    struct dm_target *ti, int result)
+{
+}
+#endif
+
+#endif
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index daa481729e9b..6650ab6def2a 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -118,6 +118,8 @@
 #define AUDIT_TIME_ADJNTPVAL	1333	/* NTP value adjustment */
 #define AUDIT_BPF		1334	/* BPF subsystem */
 #define AUDIT_EVENT_LISTENER	1335	/* Task joined multicast read socket */
+#define AUDIT_DM_CTRL		1336	/* Device Mapper target control */
+#define AUDIT_DM_EVENT		1337	/* Device Mapper events */
 
 #define AUDIT_AVC		1400	/* SE Linux avc denial or grant */
 #define AUDIT_SELINUX_ERR	1401	/* Internal SE Linux Errors */
-- 
2.20.1

[PATCH v3 2/3] dm integrity: log audit events for dm-integrity target

[Michael Weiß]

dm-integrity signals integrity violations by returning I/O errors
to user space. To identify integrity violations by a controlling
instance, the kernel audit subsystem can be used to emit audit
events to user space. We use the new dm-audit submodule allowing
to emit audit events on relevant I/O errors.

The construction and destruction of integrity device mappings are
also relevant for auditing a system. Thus, those events are also
logged as audit events.

Signed-off-by: Michael Weiß <michael.weiss@aisec.fraunhofer.de>
---
 drivers/md/dm-integrity.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
index 20f2510db1f6..a881ead4b506 100644
--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -23,6 +23,8 @@
 #include <linux/async_tx.h>
 #include <linux/dm-bufio.h>
 
+#include "dm-audit.h"
+
 #define DM_MSG_PREFIX "integrity"
 
 #define DEFAULT_INTERLEAVE_SECTORS	32768
@@ -539,6 +541,7 @@ static int sb_mac(struct dm_integrity_c *ic, bool wr)
 		}
 		if (memcmp((__u8 *)ic->sb + (1 << SECTOR_SHIFT) - size, result, size)) {
 			dm_integrity_io_error(ic, "superblock mac", -EILSEQ);
+			dm_audit_log_target(DM_MSG_PREFIX, "mac-superblock", ic->ti, 0);
 			return -EILSEQ;
 		}
 	}
@@ -876,8 +879,10 @@ static void rw_section_mac(struct dm_integrity_c *ic, unsigned section, bool wr)
 		if (likely(wr))
 			memcpy(&js->mac, result + (j * JOURNAL_MAC_PER_SECTOR), JOURNAL_MAC_PER_SECTOR);
 		else {
-			if (memcmp(&js->mac, result + (j * JOURNAL_MAC_PER_SECTOR), JOURNAL_MAC_PER_SECTOR))
+			if (memcmp(&js->mac, result + (j * JOURNAL_MAC_PER_SECTOR), JOURNAL_MAC_PER_SECTOR)) {
 				dm_integrity_io_error(ic, "journal mac", -EILSEQ);
+				dm_audit_log_target(DM_MSG_PREFIX, "mac-journal", ic->ti, 0);
+			}
 		}
 	}
 }
@@ -1782,10 +1787,15 @@ static void integrity_metadata(struct work_struct *w)
 			if (unlikely(r)) {
 				if (r > 0) {
 					char b[BDEVNAME_SIZE];
-					DMERR_LIMIT("%s: Checksum failed at sector 0x%llx", bio_devname(bio, b),
-						    (sector - ((r + ic->tag_size - 1) / ic->tag_size)));
+					sector_t s;
+
+					s = sector - ((r + ic->tag_size - 1) / ic->tag_size);
+					DMERR_LIMIT("%s: Checksum failed at sector 0x%llx",
+						    bio_devname(bio, b), s);
 					r = -EILSEQ;
 					atomic64_inc(&ic->number_of_mismatches);
+					dm_audit_log_bio(DM_MSG_PREFIX, "integrity-checksum",
+							 bio, s, 0);
 				}
 				if (likely(checksums != checksums_onstack))
 					kfree(checksums);
@@ -1991,6 +2001,8 @@ static bool __journal_read_write(struct dm_integrity_io *dio, struct bio *bio,
 					if (unlikely(memcmp(checksums_onstack, journal_entry_tag(ic, je), ic->tag_size))) {
 						DMERR_LIMIT("Checksum failed when reading from journal, at sector 0x%llx",
 							    logical_sector);
+						dm_audit_log_bio(DM_MSG_PREFIX, "journal-checksum",
+								 bio, logical_sector, 0);
 					}
 				}
 #endif
@@ -2534,8 +2546,10 @@ static void do_journal_write(struct dm_integrity_c *ic, unsigned write_start,
 
 					integrity_sector_checksum(ic, sec + ((l - j) << ic->sb->log2_sectors_per_block),
 								  (char *)access_journal_data(ic, i, l), test_tag);
-					if (unlikely(memcmp(test_tag, journal_entry_tag(ic, je2), ic->tag_size)))
+					if (unlikely(memcmp(test_tag, journal_entry_tag(ic, je2), ic->tag_size))) {
 						dm_integrity_io_error(ic, "tag mismatch when replaying journal", -EILSEQ);
+						dm_audit_log_target(DM_MSG_PREFIX, "integrity-replay-journal", ic->ti, 0);
+					}
 				}
 
 				journal_entry_set_unused(je2);
@@ -4490,9 +4504,11 @@ static int dm_integrity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 	if (ic->discard)
 		ti->num_discard_bios = 1;
 
+	dm_audit_log_ctr(DM_MSG_PREFIX, ti, 1);
 	return 0;
 
 bad:
+	dm_audit_log_ctr(DM_MSG_PREFIX, ti, 0);
 	dm_integrity_dtr(ti);
 	return r;
 }
@@ -4566,6 +4582,7 @@ static void dm_integrity_dtr(struct dm_target *ti)
 	free_alg(&ic->journal_mac_alg);
 
 	kfree(ic);
+	dm_audit_log_dtr(DM_MSG_PREFIX, ti, 1);
 }
 
 static struct target_type integrity_target = {
-- 
2.20.1

[PATCH v3 3/3] dm crypt: log aead integrity violations to audit subsystem

[Michael Weiß]

Since dm-crypt target can be stacked on dm-integrity targets to
provide authenticated encryption, integrity violations are recognized
here during aead computation. We use the dm-audit submodule to
signal those events to user space, too.

The construction and destruction of crypt device mappings are also
logged as audit events.

Signed-off-by: Michael Weiß <michael.weiss@aisec.fraunhofer.de>
---
 drivers/md/dm-crypt.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 50f4cbd600d5..5e02002345fa 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -41,6 +41,8 @@
 
 #include <linux/device-mapper.h>
 
+#include "dm-audit.h"
+
 #define DM_MSG_PREFIX "crypt"
 
 /*
@@ -1362,8 +1364,12 @@ static int crypt_convert_block_aead(struct crypt_config *cc,
 
 	if (r == -EBADMSG) {
 		char b[BDEVNAME_SIZE];
-		DMERR_LIMIT("%s: INTEGRITY AEAD ERROR, sector %llu", bio_devname(ctx->bio_in, b),
-			    (unsigned long long)le64_to_cpu(*sector));
+		sector_t s = le64_to_cpu(*sector);
+
+		DMERR_LIMIT("%s: INTEGRITY AEAD ERROR, sector %llu",
+			    bio_devname(ctx->bio_in, b), s);
+		dm_audit_log_bio(DM_MSG_PREFIX, "integrity-aead",
+				 ctx->bio_in, s, 0);
 	}
 
 	if (!r && cc->iv_gen_ops && cc->iv_gen_ops->post)
@@ -2173,8 +2179,12 @@ static void kcryptd_async_done(struct crypto_async_request *async_req,
 
 	if (error == -EBADMSG) {
 		char b[BDEVNAME_SIZE];
-		DMERR_LIMIT("%s: INTEGRITY AEAD ERROR, sector %llu", bio_devname(ctx->bio_in, b),
-			    (unsigned long long)le64_to_cpu(*org_sector_of_dmreq(cc, dmreq)));
+		sector_t s = le64_to_cpu(*org_sector_of_dmreq(cc, dmreq));
+
+		DMERR_LIMIT("%s: INTEGRITY AEAD ERROR, sector %llu",
+			    bio_devname(ctx->bio_in, b), s);
+		dm_audit_log_bio(DM_MSG_PREFIX, "integrity-aead",
+				 ctx->bio_in, s, 0);
 		io->error = BLK_STS_PROTECTION;
 	} else if (error < 0)
 		io->error = BLK_STS_IOERR;
@@ -2729,6 +2739,8 @@ static void crypt_dtr(struct dm_target *ti)
 	dm_crypt_clients_n--;
 	crypt_calculate_pages_per_client();
 	spin_unlock(&dm_crypt_clients_lock);
+
+	dm_audit_log_dtr(DM_MSG_PREFIX, ti, 1);
 }
 
 static int crypt_ctr_ivmode(struct dm_target *ti, const char *ivmode)
@@ -3357,9 +3369,11 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	ti->num_flush_bios = 1;
 	ti->limit_swap_bios = true;
 
+	dm_audit_log_ctr(DM_MSG_PREFIX, ti, 1);
 	return 0;
 
 bad:
+	dm_audit_log_ctr(DM_MSG_PREFIX, ti, 0);
 	crypt_dtr(ti);
 	return ret;
 }
-- 
2.20.1

Re: [PATCH v3 1/3] dm: introduce audit event module for device mapper

[Paul Moore]

On Tue, Aug 31, 2021 at 3:19 PM Michael Weiß
<michael.weiss@aisec.fraunhofer.de> wrote:
>
> To be able to send auditing events to user space, we introduce a
> generic dm-audit module. It provides helper functions to emit audit
> events through the kernel audit subsystem. We claim the
> AUDIT_DM_CTRL type=1336 and AUDIT_DM_EVENT type=1337 out of the
> audit event messages range in the corresponding userspace api in
> 'include/uapi/linux/audit.h' for those events.
>
> AUDIT_DM_CTRL is used to provide information about creation and
> destruction of device mapper targets which are triggered by user space
> admin control actions.
> AUDIT_DM_EVENT is used to provide information about actual errors
> during operation of the mapped device, showing e.g. integrity
> violations in audit log.
>
> Following commits to device mapper targets actually will make use of
> this to emit those events in relevant cases.
>
> The audit logs look like this if executing the following simple test:
>
>  # dd if=/dev/zero of=test.img bs=1M count=1024
>  # losetup -f test.img
>  # integritysetup -vD format --integrity sha256 -t 32 /dev/loop0
>  # integritysetup open -D /dev/loop0 --integrity sha256 integritytest
>  # integritysetup status integritytest
>  # integritysetup close integritytest
>  # integritysetup open -D /dev/loop0 --integrity sha256 integritytest
>  # integritysetup status integritytest
>  # dd if=/dev/urandom of=/dev/loop0 bs=512 count=1 seek=100000
>  # dd if=/dev/mapper/integritytest of=/dev/null
>
> -------------------------
> audit.log from auditd
>
> type=UNKNOWN[1336] msg=audit(1630425039.363:184): module=integrity
> op=ctr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
> egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
> exe="/sbin/integritysetup" subj==unconfined dev=254:3
> error_msg='success' res=1
> type=UNKNOWN[1336] msg=audit(1630425039.471:185): module=integrity
> op=dtr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
> egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
> exe="/sbin/integritysetup" subj==unconfined dev=254:3
> error_msg='success' res=1
> type=UNKNOWN[1336] msg=audit(1630425039.611:186): module=integrity
> op=ctr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
> egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
> exe="/sbin/integritysetup" subj==unconfined dev=254:3
> error_msg='success' res=1
> type=UNKNOWN[1336] msg=audit(1630425054.475:187): module=integrity
> op=dtr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
> egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
> exe="/sbin/integritysetup" subj==unconfined dev=254:3
> error_msg='success' res=1
>
> type=UNKNOWN[1336] msg=audit(1630425073.171:191): module=integrity
> op=ctr ppid=3807 pid=3883 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
> egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
> exe="/sbin/integritysetup" subj==unconfined dev=254:3
> error_msg='success' res=1
>
> type=UNKNOWN[1336] msg=audit(1630425087.239:192): module=integrity
> op=dtr ppid=3807 pid=3902 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
> egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
> exe="/sbin/integritysetup" subj==unconfined dev=254:3
> error_msg='success' res=1
>
> type=UNKNOWN[1336] msg=audit(1630425093.755:193): module=integrity
> op=ctr ppid=3807 pid=3906 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
> egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
> exe="/sbin/integritysetup" subj==unconfined dev=254:3
> error_msg='success' res=1
>
> type=UNKNOWN[1337] msg=audit(1630425112.119:194): module=integrity
> op=integrity-checksum dev=254:3 sector 77480 res=0
> type=UNKNOWN[1337] msg=audit(1630425112.119:195): module=integrity
> op=integrity-checksum dev=254:3 sector 77480 res=0
> type=UNKNOWN[1337] msg=audit(1630425112.119:196): module=integrity
> op=integrity-checksum dev=254:3 sector 77480 res=0
> type=UNKNOWN[1337] msg=audit(1630425112.119:197): module=integrity
> op=integrity-checksum dev=254:3 sector 77480 res=0
> type=UNKNOWN[1337] msg=audit(1630425112.119:198): module=integrity
> op=integrity-checksum dev=254:3 sector 77480 res=0
> type=UNKNOWN[1337] msg=audit(1630425112.119:199): module=integrity
> op=integrity-checksum dev=254:3 sector 77480 res=0
> type=UNKNOWN[1337] msg=audit(1630425112.119:200): module=integrity
> op=integrity-checksum dev=254:3 sector 77480 res=0
> type=UNKNOWN[1337] msg=audit(1630425112.119:201): module=integrity
> op=integrity-checksum dev=254:3 sector 77480 res=0
> type=UNKNOWN[1337] msg=audit(1630425112.119:202): module=integrity
> op=integrity-checksum dev=254:3 sector 77480 res=0
> type=UNKNOWN[1337] msg=audit(1630425112.119:203): module=integrity
> op=integrity-checksum dev=254:3 sector 77480 res=0
>
> Signed-off-by: Michael Weiß <michael.weiss@aisec.fraunhofer.de>
> ---
>  drivers/md/Kconfig         | 10 +++++
>  drivers/md/Makefile        |  4 ++
>  drivers/md/dm-audit.c      | 79 ++++++++++++++++++++++++++++++++++++++
>  drivers/md/dm-audit.h      | 62 ++++++++++++++++++++++++++++++
>  include/uapi/linux/audit.h |  2 +
>  5 files changed, 157 insertions(+)
>  create mode 100644 drivers/md/dm-audit.c
>  create mode 100644 drivers/md/dm-audit.h
>
> diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
> index 0602e82a9516..48adbec12148 100644
> --- a/drivers/md/Kconfig
> +++ b/drivers/md/Kconfig
> @@ -608,6 +608,7 @@ config DM_INTEGRITY
>         select CRYPTO
>         select CRYPTO_SKCIPHER
>         select ASYNC_XOR
> +       select DM_AUDIT if AUDIT
>         help
>           This device-mapper target emulates a block device that has
>           additional per-sector tags that can be used for storing
> @@ -640,4 +641,13 @@ config DM_ZONED
>
>           If unsure, say N.
>
> +config DM_AUDIT
> +       bool "DM audit events"
> +       depends on AUDIT
> +       help
> +         Generate audit events for device-mapper.
> +
> +         Enables audit logging of several security relevant events in the
> +         particular device-mapper targets, especially the integrity target.
> +
>  endif # MD
> diff --git a/drivers/md/Makefile b/drivers/md/Makefile
> index a74aaf8b1445..2f83d649500d 100644
> --- a/drivers/md/Makefile
> +++ b/drivers/md/Makefile
> @@ -103,3 +103,7 @@ endif
>  ifeq ($(CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG),y)
>  dm-verity-objs                 += dm-verity-verify-sig.o
>  endif
> +
> +ifeq ($(CONFIG_DM_AUDIT),y)
> +dm-mod-objs                    += dm-audit.o
> +endif
> diff --git a/drivers/md/dm-audit.c b/drivers/md/dm-audit.c
> new file mode 100644
> index 000000000000..761ecfdcd49a
> --- /dev/null
> +++ b/drivers/md/dm-audit.c
> @@ -0,0 +1,79 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Creating audit records for mapped devices.
> + *
> + * Copyright (C) 2021 Fraunhofer AISEC. All rights reserved.
> + *
> + * Authors: Michael Weiß <michael.weiss@aisec.fraunhofer.de>
> + */
> +
> +#include <linux/audit.h>
> +#include <linux/module.h>
> +#include <linux/device-mapper.h>
> +#include <linux/bio.h>
> +#include <linux/blkdev.h>
> +
> +#include "dm-audit.h"
> +#include "dm-core.h"
> +
> +static struct audit_buffer *dm_audit_log_start(int audit_type,
> +                                              const char *dm_msg_prefix,
> +                                              const char *op)
> +{
> +       struct audit_buffer *ab;
> +
> +       if (audit_enabled == AUDIT_OFF)
> +               return NULL;
> +
> +       ab = audit_log_start(audit_context(), GFP_KERNEL, audit_type);
> +       if (unlikely(!ab))
> +               return NULL;
> +
> +       audit_log_format(ab, "module=%s op=%s", dm_msg_prefix, op);
> +       return ab;
> +}
> +
> +void dm_audit_log_ti(int audit_type, const char *dm_msg_prefix, const char *op,
> +                    struct dm_target *ti, int result)
> +{
> +       struct audit_buffer *ab;
> +       struct mapped_device *md = dm_table_get_md(ti->table);
> +       int dev_major = dm_disk(md)->major;
> +       int dev_minor = dm_disk(md)->first_minor;
> +
> +       ab = dm_audit_log_start(audit_type, dm_msg_prefix, op);
> +       if (unlikely(!ab))
> +               return;
> +
> +       switch (audit_type) {
> +       case AUDIT_DM_CTRL:
> +               audit_log_task_info(ab);
> +               audit_log_format(ab, " dev=%d:%d error_msg='%s'", dev_major,
> +                                dev_minor, !result ? ti->error : "success");
> +               break;
> +       case AUDIT_DM_EVENT:
> +               audit_log_format(ab, " dev=%d:%d sector=?", dev_major,
> +                                dev_minor);
> +               break;
> +       }
> +       audit_log_format(ab, " res=%d", result);
> +       audit_log_end(ab);
> +}
> +EXPORT_SYMBOL_GPL(dm_audit_log_ti);

Just checking, but are you okay when the inevitable happens and
someone passes an @audit_type that is not either AUDIT_CM_CTRL or
AUDIT_DM_EVENT?  Right now that will succeed without error and give a
rather short audit record.

> +void dm_audit_log_bio(const char *dm_msg_prefix, const char *op,
> +                     struct bio *bio, sector_t sector, int result)
> +{
> +       struct audit_buffer *ab;
> +       int dev_major = MAJOR(bio->bi_bdev->bd_dev);
> +       int dev_minor = MINOR(bio->bi_bdev->bd_dev);
> +
> +       ab = dm_audit_log_start(AUDIT_DM_EVENT, dm_msg_prefix, op);
> +       if (unlikely(!ab))
> +               return;
> +
> +       audit_log_format(ab, " dev=%d:%d sector %llu res=%d",
> +                        dev_major, dev_minor, sector, result);

I think you forgot the "=" after "sector", e.g. "sector=%llu".

> +       audit_log_end(ab);
> +}
> +EXPORT_SYMBOL_GPL(dm_audit_log_bio);

-- 
paul moore
www.paul-moore.com

Re: [PATCH v3 1/3] dm: introduce audit event module for device mapper

[Weiß, Michael]

On Fri, 2021-09-03 at 13:27 -0400, Paul Moore wrote:
> On Tue, Aug 31, 2021 at 3:19 PM Michael Weiß
> <michael.weiss@aisec.fraunhofer.de> wrote:
> > To be able to send auditing events to user space, we introduce a
> > generic dm-audit module. It provides helper functions to emit audit
> > events through the kernel audit subsystem. We claim the
> > AUDIT_DM_CTRL type=1336 and AUDIT_DM_EVENT type=1337 out of the
> > audit event messages range in the corresponding userspace api in
> > 'include/uapi/linux/audit.h' for those events.
> > 
> > AUDIT_DM_CTRL is used to provide information about creation and
> > destruction of device mapper targets which are triggered by user space
> > admin control actions.
> > AUDIT_DM_EVENT is used to provide information about actual errors
> > during operation of the mapped device, showing e.g. integrity
> > violations in audit log.
> > 
> > Following commits to device mapper targets actually will make use of
> > this to emit those events in relevant cases.
> > 
> > The audit logs look like this if executing the following simple test:
> > 
> >  # dd if=/dev/zero of=test.img bs=1M count=1024
> >  # losetup -f test.img
> >  # integritysetup -vD format --integrity sha256 -t 32 /dev/loop0
> >  # integritysetup open -D /dev/loop0 --integrity sha256 integritytest
> >  # integritysetup status integritytest
> >  # integritysetup close integritytest
> >  # integritysetup open -D /dev/loop0 --integrity sha256 integritytest
> >  # integritysetup status integritytest
> >  # dd if=/dev/urandom of=/dev/loop0 bs=512 count=1 seek=100000
> >  # dd if=/dev/mapper/integritytest of=/dev/null
> > 
> > -------------------------
> > audit.log from auditd
> > 
> > type=UNKNOWN[1336] msg=audit(1630425039.363:184): module=integrity
> > op=ctr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
> > egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
> > exe="/sbin/integritysetup" subj==unconfined dev=254:3
> > error_msg='success' res=1
> > type=UNKNOWN[1336] msg=audit(1630425039.471:185): module=integrity
> > op=dtr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
> > egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
> > exe="/sbin/integritysetup" subj==unconfined dev=254:3
> > error_msg='success' res=1
> > type=UNKNOWN[1336] msg=audit(1630425039.611:186): module=integrity
> > op=ctr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
> > egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
> > exe="/sbin/integritysetup" subj==unconfined dev=254:3
> > error_msg='success' res=1
> > type=UNKNOWN[1336] msg=audit(1630425054.475:187): module=integrity
> > op=dtr ppid=3807 pid=3819 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
> > egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
> > exe="/sbin/integritysetup" subj==unconfined dev=254:3
> > error_msg='success' res=1
> > 
> > type=UNKNOWN[1336] msg=audit(1630425073.171:191): module=integrity
> > op=ctr ppid=3807 pid=3883 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
> > egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
> > exe="/sbin/integritysetup" subj==unconfined dev=254:3
> > error_msg='success' res=1
> > 
> > type=UNKNOWN[1336] msg=audit(1630425087.239:192): module=integrity
> > op=dtr ppid=3807 pid=3902 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
> > egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
> > exe="/sbin/integritysetup" subj==unconfined dev=254:3
> > error_msg='success' res=1
> > 
> > type=UNKNOWN[1336] msg=audit(1630425093.755:193): module=integrity
> > op=ctr ppid=3807 pid=3906 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0
> > egid=0 sgid=0 fsgid=0 tty=pts2 ses=3 comm="integritysetup"
> > exe="/sbin/integritysetup" subj==unconfined dev=254:3
> > error_msg='success' res=1
> > 
> > type=UNKNOWN[1337] msg=audit(1630425112.119:194): module=integrity
> > op=integrity-checksum dev=254:3 sector 77480 res=0
> > type=UNKNOWN[1337] msg=audit(1630425112.119:195): module=integrity
> > op=integrity-checksum dev=254:3 sector 77480 res=0
> > type=UNKNOWN[1337] msg=audit(1630425112.119:196): module=integrity
> > op=integrity-checksum dev=254:3 sector 77480 res=0
> > type=UNKNOWN[1337] msg=audit(1630425112.119:197): module=integrity
> > op=integrity-checksum dev=254:3 sector 77480 res=0
> > type=UNKNOWN[1337] msg=audit(1630425112.119:198): module=integrity
> > op=integrity-checksum dev=254:3 sector 77480 res=0
> > type=UNKNOWN[1337] msg=audit(1630425112.119:199): module=integrity
> > op=integrity-checksum dev=254:3 sector 77480 res=0
> > type=UNKNOWN[1337] msg=audit(1630425112.119:200): module=integrity
> > op=integrity-checksum dev=254:3 sector 77480 res=0
> > type=UNKNOWN[1337] msg=audit(1630425112.119:201): module=integrity
> > op=integrity-checksum dev=254:3 sector 77480 res=0
> > type=UNKNOWN[1337] msg=audit(1630425112.119:202): module=integrity
> > op=integrity-checksum dev=254:3 sector 77480 res=0
> > type=UNKNOWN[1337] msg=audit(1630425112.119:203): module=integrity
> > op=integrity-checksum dev=254:3 sector 77480 res=0
> > 
> > Signed-off-by: Michael Weiß <michael.weiss@aisec.fraunhofer.de>
> > ---
> >  drivers/md/Kconfig         | 10 +++++
> >  drivers/md/Makefile        |  4 ++
> >  drivers/md/dm-audit.c      | 79 ++++++++++++++++++++++++++++++++++++++
> >  drivers/md/dm-audit.h      | 62 ++++++++++++++++++++++++++++++
> >  include/uapi/linux/audit.h |  2 +
> >  5 files changed, 157 insertions(+)
> >  create mode 100644 drivers/md/dm-audit.c
> >  create mode 100644 drivers/md/dm-audit.h
> > 
> > diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
> > index 0602e82a9516..48adbec12148 100644
> > --- a/drivers/md/Kconfig
> > +++ b/drivers/md/Kconfig
> > @@ -608,6 +608,7 @@ config DM_INTEGRITY
> >         select CRYPTO
> >         select CRYPTO_SKCIPHER
> >         select ASYNC_XOR
> > +       select DM_AUDIT if AUDIT
> >         help
> >           This device-mapper target emulates a block device that has
> >           additional per-sector tags that can be used for storing
> > @@ -640,4 +641,13 @@ config DM_ZONED
> > 
> >           If unsure, say N.
> > 
> > +config DM_AUDIT
> > +       bool "DM audit events"
> > +       depends on AUDIT
> > +       help
> > +         Generate audit events for device-mapper.
> > +
> > +         Enables audit logging of several security relevant events in the
> > +         particular device-mapper targets, especially the integrity target.
> > +
> >  endif # MD
> > diff --git a/drivers/md/Makefile b/drivers/md/Makefile
> > index a74aaf8b1445..2f83d649500d 100644
> > --- a/drivers/md/Makefile
> > +++ b/drivers/md/Makefile
> > @@ -103,3 +103,7 @@ endif
> >  ifeq ($(CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG),y)
> >  dm-verity-objs                 += dm-verity-verify-sig.o
> >  endif
> > +
> > +ifeq ($(CONFIG_DM_AUDIT),y)
> > +dm-mod-objs                    += dm-audit.o
> > +endif
> > diff --git a/drivers/md/dm-audit.c b/drivers/md/dm-audit.c
> > new file mode 100644
> > index 000000000000..761ecfdcd49a
> > --- /dev/null
> > +++ b/drivers/md/dm-audit.c
> > @@ -0,0 +1,79 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Creating audit records for mapped devices.
> > + *
> > + * Copyright (C) 2021 Fraunhofer AISEC. All rights reserved.
> > + *
> > + * Authors: Michael Weiß <michael.weiss@aisec.fraunhofer.de>
> > + */
> > +
> > +#include <linux/audit.h>
> > +#include <linux/module.h>
> > +#include <linux/device-mapper.h>
> > +#include <linux/bio.h>
> > +#include <linux/blkdev.h>
> > +
> > +#include "dm-audit.h"
> > +#include "dm-core.h"
> > +
> > +static struct audit_buffer *dm_audit_log_start(int audit_type,
> > +                                              const char *dm_msg_prefix,
> > +                                              const char *op)
> > +{
> > +       struct audit_buffer *ab;
> > +
> > +       if (audit_enabled == AUDIT_OFF)
> > +               return NULL;
> > +
> > +       ab = audit_log_start(audit_context(), GFP_KERNEL, audit_type);
> > +       if (unlikely(!ab))
> > +               return NULL;
> > +
> > +       audit_log_format(ab, "module=%s op=%s", dm_msg_prefix, op);
> > +       return ab;
> > +}
> > +
> > +void dm_audit_log_ti(int audit_type, const char *dm_msg_prefix, const char *op,
> > +                    struct dm_target *ti, int result)
> > +{
> > +       struct audit_buffer *ab;
> > +       struct mapped_device *md = dm_table_get_md(ti->table);
> > +       int dev_major = dm_disk(md)->major;
> > +       int dev_minor = dm_disk(md)->first_minor;
> > +
> > +       ab = dm_audit_log_start(audit_type, dm_msg_prefix, op);
> > +       if (unlikely(!ab))
> > +               return;
> > +
> > +       switch (audit_type) {
> > +       case AUDIT_DM_CTRL:
> > +               audit_log_task_info(ab);
> > +               audit_log_format(ab, " dev=%d:%d error_msg='%s'", dev_major,
> > +                                dev_minor, !result ? ti->error : "success");
> > +               break;
> > +       case AUDIT_DM_EVENT:
> > +               audit_log_format(ab, " dev=%d:%d sector=?", dev_major,
> > +                                dev_minor);
> > +               break;
> > +       }
> > +       audit_log_format(ab, " res=%d", result);
> > +       audit_log_end(ab);
> > +}
> > +EXPORT_SYMBOL_GPL(dm_audit_log_ti);
> 
> Just checking, but are you okay when the inevitable happens and
> someone passes an @audit_type that is not either AUDIT_CM_CTRL or
> AUDIT_DM_EVENT?  Right now that will succeed without error and give a
> rather short audit record.
> 
Well, this function is not intended to be called directly from other dm
modules. Only the corresponding wrapper functions in dm-audit.h should
be called. I will add a comment in the header and provide a default case
which does not log anything here.

> > +void dm_audit_log_bio(const char *dm_msg_prefix, const char *op,
> > +                     struct bio *bio, sector_t sector, int result)
> > +{
> > +       struct audit_buffer *ab;
> > +       int dev_major = MAJOR(bio->bi_bdev->bd_dev);
> > +       int dev_minor = MINOR(bio->bi_bdev->bd_dev);
> > +
> > +       ab = dm_audit_log_start(AUDIT_DM_EVENT, dm_msg_prefix, op);
> > +       if (unlikely(!ab))
> > +               return;
> > +
> > +       audit_log_format(ab, " dev=%d:%d sector %llu res=%d",
> > +                        dev_major, dev_minor, sector, result);
> 
> I think you forgot the "=" after "sector", e.g. "sector=%llu".
> 
Damn, you are right. I'll fix that.

> > +       audit_log_end(ab);
> > +}
> > +EXPORT_SYMBOL_GPL(dm_audit_log_bio);

-- 
Thanks,
Michael