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

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Message-Id: <20210812145748.4460-3-michael.weiss@aisec.fraunhofer.de>
Date:   Thu, 12 Aug 2021 16:57:43 +0200
From:   Michael Weiß <michael.weiss@...ec.fraunhofer.de>
To:     michael.weiss@...ec.fraunhofer.de
Cc:     Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com,
        Song Liu <song@...nel.org>, Paul Moore <paul@...l-moore.com>,
        Eric Paris <eparis@...hat.com>, linux-kernel@...r.kernel.org,
        linux-raid@...r.kernel.org, linux-audit@...hat.com
Subject: [PATCH 2/3] dm integrity: log audit events for dm-integrity target

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@...ec.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..fbbb4c3f16cb 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_target(DM_MSG_PREFIX, "ctr", ti, 1);
 	return 0;
 
 bad:
+	dm_audit_log_target(DM_MSG_PREFIX, "ctr", 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_target(DM_MSG_PREFIX, "dtr", ti, 1);
 }
 
 static struct target_type integrity_target = {
-- 
2.20.1