dm ima: fix wrong length calculation for no_data string

Commit Message

Thore Sommer Jan. 25, 2022, 2:05 p.m. UTC

All entries measured by dm ima are prefixed by a version string
(dm_version=N.N.N). When there is no data to measure, the entire buffer is
overwritten with a string containing the version string again and the
length of that string is added to the length of the version string.
The new length is now wrong because it contains the version string twice.

This caused entries like this:
dm_version=4.45.0;name=test,uuid=test;table_clear=no_data; \
\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00 \
current_device_capacity=204808;

Signed-off-by: Thore Sommer <[e-mail]>
---
 drivers/md/dm-ima.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Patch

diff --git a/drivers/md/dm-ima.c b/drivers/md/dm-ima.c
index 957999998d70..1842d3a958ef 100644
--- a/drivers/md/dm-ima.c
+++ b/drivers/md/dm-ima.c
@@ -455,7 +455,7 @@  void dm_ima_measure_on_device_resume(struct mapped_device *md, bool swap)
 		scnprintf(device_table_data, DM_IMA_DEVICE_BUF_LEN,
 			  "%sname=%s,uuid=%s;device_resume=no_data;",
 			  DM_IMA_VERSION_STR, dev_name, dev_uuid);
-		l += strlen(device_table_data);
+		l = strlen(device_table_data);
 
 	}
 
@@ -568,7 +568,7 @@  void dm_ima_measure_on_device_remove(struct mapped_device *md, bool remove_all)
 		scnprintf(device_table_data, DM_IMA_DEVICE_BUF_LEN,
 			  "%sname=%s,uuid=%s;device_remove=no_data;",
 			  DM_IMA_VERSION_STR, dev_name, dev_uuid);
-		l += strlen(device_table_data);
+		l = strlen(device_table_data);
 	}
 
 	memcpy(device_table_data + l, remove_all_str, remove_all_len);
@@ -654,7 +654,7 @@  void dm_ima_measure_on_table_clear(struct mapped_device *md, bool new_map)
 		scnprintf(device_table_data, DM_IMA_DEVICE_BUF_LEN,
 			  "%sname=%s,uuid=%s;table_clear=no_data;",
 			   DM_IMA_VERSION_STR, dev_name, dev_uuid);
-		l += strlen(device_table_data);
+		l = strlen(device_table_data);
 	}
 
 	capacity_len = strlen(capacity_str);