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SubjectRe: [PATCH v3] cred: Propagate security_prepare_creds() error code
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;

> 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?

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

- Eric

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