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SubjectRe: [PATCH 1/2] ima: split ima_add_digest_entry() function
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On Wed, 2011-11-16 at 11:10 +0100, Roberto Sassu wrote:
> The ima_add_digest_entry() function has been split in order to avoid
> adding an entry in the measurements list for which the PCR extend
> operation subsequently fails. Required memory is allocated earlier in the
> new function ima_prepare_template_entry() and the template entry is added
> after ima_pcr_extend().
>
> Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>

Not adding a measurement would certainly resolve the problems with
validating the measurement list against the PCR, but poses a risk that
something was read/executed that wasn't included in the measurement
list. One solution would be for IMA to queue these measurements for the
TPM, but, I think, a better solution would be for the tpm driver to
queue them.

thanks,

Mimi

> ---
> security/integrity/ima/ima_queue.c | 35 ++++++++++++++++++++++++++---------
> 1 files changed, 26 insertions(+), 9 deletions(-)
>
> diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
> index 8e28f04..ddc7e18 100644
> --- a/security/integrity/ima/ima_queue.c
> +++ b/security/integrity/ima/ima_queue.c
> @@ -59,30 +59,41 @@ static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value)
> return ret;
> }
>
> -/* ima_add_template_entry helper function:
> - * - Add template entry to measurement list and hash table.
> +/* ima_prepare_template_entry helper function:
> + * - prepare template entry before adding it to the measurement list.
> *
> * (Called with ima_extend_list_mutex held.)
> */
> -static int ima_add_digest_entry(struct ima_template_entry *entry)
> +static struct ima_queue_entry *ima_prepare_template_entry(
> + struct ima_template_entry *entry)
> {
> struct ima_queue_entry *qe;
> - unsigned int key;
>
> qe = kmalloc(sizeof(*qe), GFP_KERNEL);
> if (qe == NULL) {
> pr_err("IMA: OUT OF MEMORY ERROR creating queue entry.\n");
> - return -ENOMEM;
> + goto out;
> }
> qe->entry = entry;
> +out:
> + return qe;
> +}
> +
> +/* ima_add_digest_entry helper function:
> + * - Add template entry to measurement list and hash table.
> + *
> + * (Called with ima_extend_list_mutex held.)
> + */
> +static void ima_add_digest_entry(struct ima_queue_entry *qe)
> +{
> + unsigned int key;
>
> INIT_LIST_HEAD(&qe->later);
> list_add_tail_rcu(&qe->later, &ima_measurements);
>
> atomic_long_inc(&ima_htable.len);
> - key = ima_hash_key(entry->digest);
> + key = ima_hash_key(qe->entry->digest);
> hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
> - return 0;
> }
>
> static int ima_pcr_extend(const u8 *hash)
> @@ -104,6 +115,7 @@ static int ima_pcr_extend(const u8 *hash)
> int ima_add_template_entry(struct ima_template_entry *entry, int violation,
> const char *op, struct inode *inode)
> {
> + struct ima_queue_entry *qe;
> u8 digest[IMA_DIGEST_SIZE];
> const char *audit_cause = "hash_added";
> int audit_info = 1;
> @@ -118,10 +130,11 @@ int ima_add_template_entry(struct ima_template_entry *entry, int violation,
> }
> }
>
> - result = ima_add_digest_entry(entry);
> - if (result < 0) {
> + qe = ima_prepare_template_entry(entry);
> + if (qe == NULL) {
> audit_cause = "ENOMEM";
> audit_info = 0;
> + result = -ENOMEM;
> goto out;
> }
>
> @@ -132,7 +145,11 @@ int ima_add_template_entry(struct ima_template_entry *entry, int violation,
> if (result != 0) {
> audit_cause = "TPM error";
> audit_info = 0;
> + kfree(qe);
> + goto out;
> }
> +
> + ima_add_digest_entry(qe);
> out:
> mutex_unlock(&ima_extend_list_mutex);
> integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,




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