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SubjectRe: [PATCH v3] cred: Propagate security_prepare_creds() error code
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Hi Eric,

On 6/9/22 6:18 PM, Eric Biggers wrote:
> On Wed, Jun 08, 2022 at 10:09:42AM -0500, Frederick Lawler wrote:
>> diff --git a/fs/aio.c b/fs/aio.c
>> index 3c249b938632..5abbe88c3ca7 100644
>> --- a/fs/aio.c
>> +++ b/fs/aio.c
>> @@ -1620,6 +1620,8 @@ static void aio_fsync_work(struct work_struct *work)
>> static int aio_fsync(struct fsync_iocb *req, const struct iocb *iocb,
>> bool datasync)
>> {
>> + int err;
>> +
>> if (unlikely(iocb->aio_buf || iocb->aio_offset || iocb->aio_nbytes ||
>> iocb->aio_rw_flags))
>> return -EINVAL;
>> @@ -1628,8 +1630,11 @@ static int aio_fsync(struct fsync_iocb *req, const struct iocb *iocb,
>> return -EINVAL;
>>
>> req->creds = prepare_creds();
>> - if (!req->creds)
>> - return -ENOMEM;
>> + if (IS_ERR(req->creds)) {
>> + err = PTR_ERR(req->creds);
>> + req->creds = NULL;
>> + return err;
>> + }
>
> This part is a little ugly. How about doing:
>
> creds = prepare_creds();
> if (IS_ERR(creds))
> return PTR_ERR(creds);
> req->creds = creds;
>

I can do that, and same for below.

>> diff --git a/fs/exec.c b/fs/exec.c
>> index 0989fb8472a1..02624783e40e 100644
>> --- a/fs/exec.c
>> +++ b/fs/exec.c
>> @@ -1468,15 +1468,19 @@ EXPORT_SYMBOL(finalize_exec);
>> */
>> static int prepare_bprm_creds(struct linux_binprm *bprm)
>> {
>> + int err = -ERESTARTNOINTR;
>> if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
>> - return -ERESTARTNOINTR;
>> + return err;
>>
>> bprm->cred = prepare_exec_creds();
>> - if (likely(bprm->cred))
>> - return 0;
>> + if (IS_ERR(bprm->cred)) {
>> + err = PTR_ERR(bprm->cred);
>> + bprm->cred = NULL;
>> + mutex_unlock(&current->signal->cred_guard_mutex);
>> + return err;
>> + }
>>
>> - mutex_unlock(&current->signal->cred_guard_mutex);
>> - return -ENOMEM;
>> + return 0;
>> }
>
> Similarly:
>
> static int prepare_bprm_creds(struct linux_binprm *bprm)
> {
> struct cred *cred;
>
> if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
> return -ERESTARTNOINTR;
>
> cred = prepare_exec_creds();
> if (IS_ERR(cred)) {
> mutex_unlock(&current->signal->cred_guard_mutex);
> return PTR_ERR(cred);
> }
> bprm->cred = cred;
> return 0;
> }
>
>> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
>> index eec72ca962e2..6cf75aa83b6c 100644
>> --- a/kernel/nsproxy.c
>> +++ b/kernel/nsproxy.c
>> @@ -311,6 +311,7 @@ static void put_nsset(struct nsset *nsset)
>>
>> static int prepare_nsset(unsigned flags, struct nsset *nsset)
>> {
>> + int err = -ENOMEM;
>> struct task_struct *me = current;
>>
>> nsset->nsproxy = create_new_namespaces(0, me, current_user_ns(), me->fs);
>> @@ -324,6 +325,12 @@ static int prepare_nsset(unsigned flags, struct nsset *nsset)
>> if (!nsset->cred)
>> goto out;
>>
>> + if (IS_ERR(nsset->cred)) {
>> + err = PTR_ERR(nsset->cred);
>> + nsset->cred = NULL;
>> + goto out;
>> + }
>
> Why is the NULL check above being kept?
>

In the branch prior:

if (flags & CLONE_NEWUSER) {
nsset->cred = prepare_creds();
else
nsset->cred = current_cred();

I don't see cases where others are checking for null after
current_cred(), therefore I can remove that check.

> Also, drivers/crypto/ccp/sev-dev.c needs to be updated.
>

Nice catch! I clearly missed addition after the merge window.

> - Eric

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