The avb_ops.h header file, which has been imported from the upstream
libavb, says:
/* Reads a persistent value corresponding to the given |name|. The value is
* returned in |out_buffer| which must point to |buffer_size| bytes. On
* success |out_num_bytes_read| contains the number of bytes read into
* |out_buffer|. If AVB_IO_RESULT_ERROR_INSUFFICIENT_SPACE is returned,
* |out_num_bytes_read| contains the number of bytes that would have been
read
* which can be used to allocate a buffer.
The invoke_func() wrapper does translate a TEE_ERROR_STORAGE_NO_SPACE
return to AVB_IO_RESULT_ERROR_INSUFFICIENT_SPACE. However, this
implementation of the read_persistent_value method currently never
updates *out_num_bytes_read in case of an error.
Also note that currently, at least the upstream optee-os
implementation of TA_AVB_CMD_READ_PERSIST_VALUE never returns
TEE_ERROR_STORAGE_NO_SPACE, but instead silently returns a truncated
value, with no way for the caller to know that happened. A fix has
been proposed (https://github.com/OP-TEE/optee_os/pull/7959).
Signed-off-by: Rasmus Villemoes <[email protected]>
---
common/avb_verify.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/common/avb_verify.c b/common/avb_verify.c
index 76c523fd0ba..af166e7dfba 100644
--- a/common/avb_verify.c
+++ b/common/avb_verify.c
@@ -963,8 +963,11 @@ static AvbIOResult read_persistent_value(AvbOps *ops,
rc = invoke_func(ops->user_data, TA_AVB_CMD_READ_PERSIST_VALUE,
2, param);
- if (rc)
+ if (rc) {
+ if (rc == AVB_IO_RESULT_ERROR_INSUFFICIENT_SPACE)
+ *out_num_bytes_read = param[1].u.memref.size;
goto out;
+ }
if (param[1].u.memref.size > buffer_size) {
rc = AVB_IO_RESULT_ERROR_NO_SUCH_VALUE;
--
2.55.0
