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dm ima: measure data on device remove

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Presence of an active block-device, configured with expected parameters,
is important for an external attestation service to determine if a system
meets the attestation requirements.  Therefore it is important for DM to
measure the device remove events.

Measure device parameters and table hashes when the device is removed,
using either remove or remove_all.

Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Tushar Sugandhi 2021-07-12 17:49:00 -07:00 committed by Mike Snitzer
parent 8eb6fab402
commit 84010e519f
3 changed files with 124 additions and 0 deletions
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119
drivers/md/dm-ima.c
View File

@ -444,3 +444,122 @@ error:
kfree(capacity_str);
kfree(device_table_data);
}
/*
* Measure IMA data on remove.
*/
void dm_ima_measure_on_device_remove(struct mapped_device *md, bool remove_all)
{
char *device_table_data, *dev_name = NULL, *dev_uuid = NULL, *capacity_str = NULL;
char active_table_str[] = "active_table_hash=";
char inactive_table_str[] = "inactive_table_hash=";
char device_active_str[] = "device_active_metadata=";
char device_inactive_str[] = "device_inactive_metadata=";
char remove_all_str[] = "remove_all=";
unsigned int active_table_len = strlen(active_table_str);
unsigned int inactive_table_len = strlen(inactive_table_str);
unsigned int device_active_len = strlen(device_active_str);
unsigned int device_inactive_len = strlen(device_inactive_str);
unsigned int remove_all_len = strlen(remove_all_str);
unsigned int capacity_len = 0;
unsigned int l = 0;
bool noio = true;
int r;
device_table_data = dm_ima_alloc(DM_IMA_DEVICE_BUF_LEN*2, GFP_KERNEL, noio);
if (!device_table_data)
goto exit;
r = dm_ima_alloc_and_copy_capacity_str(md, &capacity_str, noio);
if (r) {
kfree(device_table_data);
goto exit;
}
if (md->ima.active_table.device_metadata) {
memcpy(device_table_data + l, device_active_str, device_active_len);
l += device_active_len;
memcpy(device_table_data + l, md->ima.active_table.device_metadata,
md->ima.active_table.device_metadata_len);
l += md->ima.active_table.device_metadata_len;
}
if (md->ima.inactive_table.device_metadata) {
memcpy(device_table_data + l, device_inactive_str, device_inactive_len);
l += device_inactive_len;
memcpy(device_table_data + l, md->ima.inactive_table.device_metadata,
md->ima.inactive_table.device_metadata_len);
l += md->ima.inactive_table.device_metadata_len;
}
if (md->ima.active_table.hash) {
memcpy(device_table_data + l, active_table_str, active_table_len);
l += active_table_len;
memcpy(device_table_data + l, md->ima.active_table.hash,
md->ima.active_table.hash_len);
l += md->ima.active_table.hash_len;
memcpy(device_table_data + l, ",", 1);
l++;
}
if (md->ima.inactive_table.hash) {
memcpy(device_table_data + l, inactive_table_str, inactive_table_len);
l += inactive_table_len;
memcpy(device_table_data + l, md->ima.inactive_table.hash,
md->ima.inactive_table.hash_len);
l += md->ima.inactive_table.hash_len;
memcpy(device_table_data + l, ",", 1);
l++;
}
/*
* In case both active and inactive tables, and corresponding
* device metadata is cleared/missing - record the name and uuid
* in IMA measurements.
*/
if (!l) {
if (dm_ima_alloc_and_copy_name_uuid(md, &dev_name, &dev_uuid, noio))
goto error;
scnprintf(device_table_data, DM_IMA_DEVICE_BUF_LEN,
"name=%s,uuid=%s;device_remove=no_data;",
dev_name, dev_uuid);
l += strlen(device_table_data);
}
memcpy(device_table_data + l, remove_all_str, remove_all_len);
l += remove_all_len;
memcpy(device_table_data + l, remove_all ? "y;" : "n;", 2);
l += 2;
capacity_len = strlen(capacity_str);
memcpy(device_table_data + l, capacity_str, capacity_len);
l += capacity_len;
dm_ima_measure_data("device_remove", device_table_data, l, noio);
error:
kfree(device_table_data);
kfree(capacity_str);
exit:
kfree(md->ima.active_table.device_metadata);
if (md->ima.active_table.device_metadata !=
md->ima.inactive_table.device_metadata)
kfree(md->ima.inactive_table.device_metadata);
kfree(md->ima.active_table.hash);
if (md->ima.active_table.hash != md->ima.inactive_table.hash)
kfree(md->ima.inactive_table.hash);
dm_ima_reset_data(md);
kfree(dev_name);
kfree(dev_uuid);
}

2
drivers/md/dm-ima.h
View File

@ -50,12 +50,14 @@ struct dm_ima_measurements {
void dm_ima_reset_data(struct mapped_device *md);
void dm_ima_measure_on_table_load(struct dm_table *table, unsigned int status_flags);
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);
#else
static inline void dm_ima_reset_data(struct mapped_device *md) {}
static inline void dm_ima_measure_on_table_load(struct dm_table *table, unsigned int status_flags) {}
static inline void dm_ima_measure_on_device_resume(struct mapped_device *md, bool swap) {}
static inline void dm_ima_measure_on_device_remove(struct mapped_device *md, bool remove_all) {}
#endif /* CONFIG_IMA */

3
drivers/md/dm-ioctl.c
View File

@ -348,6 +348,7 @@ retry:
dm_sync_table(md);
dm_table_destroy(t);
}
dm_ima_measure_on_device_remove(md, true);
dm_put(md);
if (likely(keep_open_devices))
dm_destroy(md);
@ -982,6 +983,8 @@ static int dev_remove(struct file *filp, struct dm_ioctl *param, size_t param_si
param->flags &= ~DM_DEFERRED_REMOVE;
dm_ima_measure_on_device_remove(md, false);
if (!dm_kobject_uevent(md, KOBJ_REMOVE, param->event_nr))
param->flags |= DM_UEVENT_GENERATED_FLAG;