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SubjectRe: [PATCH v2 2/3] IMA: Add log statements for failure conditions.
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Hi Joe,

On 2020-02-10 7:23 p.m., Joe Perches wrote:
> On Mon, 2020-02-10 at 18:47 -0800, Tushar Sugandhi wrote:
>> process_buffer_measurement() and ima_alloc_key_entry()
>> functions do not have log messages for failure conditions.
>
> trivia:
>
>> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> []
>> @@ -757,6 +757,9 @@ void process_buffer_measurement(const void *buf, int size,
>> ima_free_template_entry(entry);
>>
>> out:
>> + if (ret < 0)
>> + pr_err("Process buffer measurement failed, result: %d\n", ret);
>
> perhaps use %s, __func__
>
> pr_err("%s: failed, result: %d\n", __func__, ret);
>
Sounds good. Will make this change in the next update.
>> diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
> []
>> @@ -90,6 +90,7 @@ static struct ima_key_entry *ima_alloc_key_entry(struct key *keyring,
>>
>> out:
>> if (rc) {
>> + pr_err("Key entry allocation failed, result: %d\n", rc);
>> ima_free_key_entry(entry);
>> entry = NULL;
>> }
>
> Likely the pr_err is unnecessary here as kmalloc, kstrdup
> and kmemdup all emit a dump_stack() on allocation failure.
Thanks for pointing out kmalloc, kstrdup, and kmemdup emit a
dump_stack(). But keeping the above pr_err() will help associate the
failure with IMA.
For instance - "dmesg | grep ima:" will include this error.
Perhaps I should add __func__ here as well.
And since we are redefining the pr_fmt to prefix module and base names,
it will help further to pinpoint where exactly the failure is coming from.

>
> Perhaps instead:
>
> o Remove unnecessary indentation in ima_free_key_entry by
> returning early on NULL argument
> o Remove unnecessary rc, tests and label in ima_alloc_key_entry
> ---
> security/integrity/ima/ima_queue_keys.c | 37 +++++++++++++--------------------
> 1 file changed, 15 insertions(+), 22 deletions(-)
>
> diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
> index c87c722..ba449f 100644
> --- a/security/integrity/ima/ima_queue_keys.c
> +++ b/security/integrity/ima/ima_queue_keys.c
> @@ -58,42 +58,35 @@ void ima_init_key_queue(void)
>
> static void ima_free_key_entry(struct ima_key_entry *entry)
> {
> - if (entry) {
> - kfree(entry->payload);
> - kfree(entry->keyring_name);
> - kfree(entry);
> - }
> + if (!entry)
> + return;
> +
> + kfree(entry->payload);
> + kfree(entry->keyring_name);
> + kfree(entry);
> }
>
Thanks for the feedback. Appreciate it. I would like to make this fix.
But I am not sure if this patchset, which mainly focuses on improving
logging in IMA, is the right patchset for this.
> static struct ima_key_entry *ima_alloc_key_entry(struct key *keyring,
> const void *payload,
> size_t payload_len)
> {
> - int rc = 0;
> struct ima_key_entry *entry;
>
> entry = kzalloc(sizeof(*entry), GFP_KERNEL);
> - if (entry) {
> - entry->payload = kmemdup(payload, payload_len, GFP_KERNEL);
> - entry->keyring_name = kstrdup(keyring->description,
> - GFP_KERNEL);
> - entry->payload_len = payload_len;
> - }
> -
> - if ((entry == NULL) || (entry->payload == NULL) ||
> - (entry->keyring_name == NULL)) {
> - rc = -ENOMEM;
> - goto out;
> - }
> + if (!entry)
> + return NULL;
>
> - INIT_LIST_HEAD(&entry->list);
> + entry->payload = kmemdup(payload, payload_len, GFP_KERNEL);
> + entry->payload_len = payload_len;
> + entry->keyring_name = kstrdup(keyring->description, GFP_KERNEL);
>
> -out:
> - if (rc) {
> + if (!entry->payload || !entry->keyring_name) {
> ima_free_key_entry(entry);
> - entry = NULL;
> + return NULL;
> }
>
> + INIT_LIST_HEAD(&entry->list);
> +
> return entry;
> }
>
>
Thanks again. This recommended change certainly makes the code more
readable. But again, I am not sure if this patchset is the right one for
this proposed change.
Perhaps I can create another patchset for the above two recommended
changes, and only focus on improving logging in this patchset?

Thanks,
Tushar

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