Hi Lakshmi,
On 06.05.22 22:25, Lakshmi Ramasubramanian wrote:
Hi Thore,
On 1/6/2022 12:34 PM, Thore Sommer wrote:
A new DM event dm_target_update is introduced for targets to remeasure
their table entry. This is intended for targets that indicate security
relevant events by updating one of their table entries (e.g. verity for
corruption).
In the patch description please state the existing problem (or,
limitation in the existing implementation) and then describe how the
proposed change addresses the issue.
For v2 I will add the problem description from the cover letter also to
this patch description.
In the event the dm version, device metadata and target data gets
measured.
This does not update the hash of the active table because it would
require
to rehash the whole table with all the other targets entries.
Signed-off-by: Thore Sommer <public@xxxxxxxx>
---
drivers/md/dm-ima.c | 76 +++++++++++++++++++++++++++++++++++++++++++++
drivers/md/dm-ima.h | 2 ++
2 files changed, 78 insertions(+)
diff --git a/drivers/md/dm-ima.c b/drivers/md/dm-ima.c
index 957999998d70..3b1bb97263d9 100644
--- a/drivers/md/dm-ima.c
+++ b/drivers/md/dm-ima.c
@@ -750,3 +750,79 @@ void dm_ima_measure_on_device_rename(struct
mapped_device *md)
kfree(new_dev_name);
kfree(new_dev_uuid);
}
+
+/*
+ * Give the option for targets to remeasure on state change.
+ */
+void dm_ima_measure_on_target_update(struct dm_target *ti)
+{
+ char *ima_buf = NULL, *target_metadata_buf = NULL,
*target_data_buf = NULL;
+ struct dm_target *ti2;
+ size_t target_metadata_buf_len, target_data_buf_len;
+ unsigned int num_targets, target_index;
+ struct dm_table *table = ti->table;
+ struct mapped_device *md = table->md;
+ bool found = false;
+ bool noio = true;
+ int l = 0;
+
Initializing "ima_buf" to NULL is not necessary since the statement
below initializes it.
Yes, I will remove that.
+ ima_buf = dm_ima_alloc(DM_IMA_MEASUREMENT_BUF_LEN, GFP_KERNEL,
noio);
+ if (!ima_buf)
+ return;
+
+ target_metadata_buf =
dm_ima_alloc(DM_IMA_TARGET_METADATA_BUF_LEN, GFP_KERNEL, noio);
+ if (!target_metadata_buf)
+ goto exit;
+
+ target_data_buf = dm_ima_alloc(DM_IMA_TARGET_DATA_BUF_LEN,
GFP_KERNEL, noio);
+ if (!target_data_buf)
+ goto exit;
+
+ /*
+ * Get the index of the target in the table.
+ */
+ num_targets = dm_table_get_num_targets(table);
+ for (target_index = 0; target_index < num_targets; target_index++) {
+ ti2 = dm_table_get_target(table, target_index);
+ if (!ti)
+ goto exit;
This check for "ti" can be done on function entry to avoid memory
allocations and calls to dm_table_get_num_targets(),
dm_table_get_target() when "ti" is NULL.
I actually wanted to check for ti2, but I think this entire loop can be
simplified to:
num_targets = dm_table_get_num_targets(table);
for (target_index = 0; target_index < num_targets; target_index++) {
ti2 = dm_table_get_target(table, target_index);
if (ti == ti2)
break;
}
if (target_index == num_targets)
goto exit;
This should work and because we iterate over all targets and if we
iterated over all and did not find a match then we skip the measuring.
I do not know if checking if "ti" is NULL is required because it should
never be NULL in my understanding.
+ if (ti == ti2) {
+ found = true;
+ break;
+ }
+ }
+ if (!found)
+ goto exit;
+
+ scnprintf(target_metadata_buf, DM_IMA_TARGET_METADATA_BUF_LEN,
+ "target_index=%d,target_begin=%llu,target_len=%llu,",
+ target_index, ti->begin, ti->len);
Check return status of "scnprintf()" and handle any error.
The other code in dm-ima.c also does not check for errors "scnprintf()".
Do you have an example on how to handle "scnprintf()" errors?
Regards,
Thore
thanks,
-lakshmi
+ target_metadata_buf_len = strlen(target_metadata_buf);
+
+ if (ti->type->status)
+ ti->type->status(ti, STATUSTYPE_IMA, STATUSTYPE_IMA,
target_data_buf,
+ DM_IMA_TARGET_DATA_BUF_LEN);
+ else
+ target_data_buf[0] = '\0';
+ target_data_buf_len = strlen(target_data_buf);
+
+ memcpy(ima_buf + l, DM_IMA_VERSION_STR, md->ima.dm_version_str_len);
+ l += md->ima.dm_version_str_len;
+
+ memcpy(ima_buf + l, md->ima.active_table.device_metadata,
+ md->ima.active_table.device_metadata_len);
+ l += md->ima.active_table.device_metadata_len;
+
+ memcpy(ima_buf + l, target_metadata_buf, target_metadata_buf_len);
+ l += target_metadata_buf_len;
+
+ memcpy(ima_buf + l, target_data_buf, target_data_buf_len);
+
+ dm_ima_measure_data("dm_target_update", ima_buf, strlen(ima_buf),
noio);
+
+exit:
+ kfree(ima_buf);
+ kfree(target_data_buf);
+ kfree(target_metadata_buf);
+}
+EXPORT_SYMBOL_GPL(dm_ima_measure_on_target_update);
diff --git a/drivers/md/dm-ima.h b/drivers/md/dm-ima.h
index b8c3b614670b..281a8b65f8a9 100644
--- a/drivers/md/dm-ima.h
+++ b/drivers/md/dm-ima.h
@@ -63,6 +63,7 @@ void dm_ima_measure_on_device_resume(struct
mapped_device *md, bool swap);
void dm_ima_measure_on_device_remove(struct mapped_device *md, bool
remove_all);
void dm_ima_measure_on_table_clear(struct mapped_device *md, bool
new_map);
void dm_ima_measure_on_device_rename(struct mapped_device *md);
+void dm_ima_measure_on_target_update(struct dm_target *ti);
#else
@@ -72,6 +73,7 @@ static inline void
dm_ima_measure_on_device_resume(struct mapped_device *md, boo
static inline void dm_ima_measure_on_device_remove(struct
mapped_device *md, bool remove_all) {}
static inline void dm_ima_measure_on_table_clear(struct
mapped_device *md, bool new_map) {}
static inline void dm_ima_measure_on_device_rename(struct
mapped_device *md) {}
+static inline void dm_ima_measure_on_target_update(struct dm_target
*ti) {}
#endif /* CONFIG_IMA */
