Re: [PATCH v2 2/3] remoteproc: Introduce deny_sysfs_ops flag

Bjorn Andersson
2020-11-21T03:38:16Z

On Fri 20 Nov 21:01 CST 2020, Suman Anna wrote:

> The remoteproc framework provides sysfs interfaces for changing
> the firmware name and for starting/stopping a remote processor
> through the sysfs files 'state' and 'firmware'. The 'recovery'
> sysfs file can also be used similarly to control the error recovery
> state machine of a remoteproc. These interfaces are currently
> allowed irrespective of how the remoteprocs were booted (like
> remoteproc self auto-boot, remoteproc client-driven boot etc).
> These interfaces can adversely affect a remoteproc and its clients
> especially when a remoteproc is being controlled by a remoteproc
> client driver(s). Also, not all remoteproc drivers may want to
> support the sysfs interfaces by default.
>
> Add support to deny the sysfs state/firmware/recovery change by
> introducing a state flag 'deny_sysfs_ops' that the individual
> remoteproc drivers can set based on their usage needs. The default
> behavior is to allow the sysfs operations as before.
>

This makes sense, but can't we implement attribute_group->is_visible to
simply hide these entries from userspace instead of leaving them
"broken"?

Regards,
Bjorn

> Signed-off-by: Suman Anna <s-anna@ti.com>
> ---
> v2: revised to account for the 'recovery' sysfs file as well, patch
> description updated accordingly
> v1: https://patchwork.kernel.org/project/linux-remoteproc/patch/20180915003725.17549-5-s-anna@ti.com/
>
> drivers/remoteproc/remoteproc_sysfs.c | 12 ++++++++++++
> include/linux/remoteproc.h | 2 ++
> 2 files changed, 14 insertions(+)
>
> diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
> index bd2950a246c9..3fd18a71c188 100644
> --- a/drivers/remoteproc/remoteproc_sysfs.c
> +++ b/drivers/remoteproc/remoteproc_sysfs.c
> @@ -49,6 +49,10 @@ static ssize_t recovery_store(struct device *dev,
> {
> struct rproc *rproc = to_rproc(dev);
>
> + /* restrict sysfs operations if not allowed by remoteproc drivers */
> + if (rproc->deny_sysfs_ops)
> + return -EPERM;
> +
> if (sysfs_streq(buf, "enabled")) {
> /* change the flag and begin the recovery process if needed */
> rproc->recovery_disabled = false;
> @@ -158,6 +162,10 @@ static ssize_t firmware_store(struct device *dev,
> char *p;
> int err, len = count;
>
> + /* restrict sysfs operations if not allowed by remoteproc drivers */
> + if (rproc->deny_sysfs_ops)
> + return -EPERM;
> +
> err = mutex_lock_interruptible(&rproc->lock);
> if (err) {
> dev_err(dev, "can't lock rproc %s: %d\n", rproc->name, err);
> @@ -225,6 +233,10 @@ static ssize_t state_store(struct device *dev,
> struct rproc *rproc = to_rproc(dev);
> int ret = 0;
>
> + /* restrict sysfs operations if not allowed by remoteproc drivers */
> + if (rproc->deny_sysfs_ops)
> + return -EPERM;
> +
> if (sysfs_streq(buf, "start")) {
> if (rproc->state == RPROC_RUNNING)
> return -EBUSY;
> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> index 3fa3ba6498e8..dbc3767f7d0e 100644
> --- a/include/linux/remoteproc.h
> +++ b/include/linux/remoteproc.h
> @@ -508,6 +508,7 @@ struct rproc_dump_segment {
> * @has_iommu: flag to indicate if remote processor is behind an MMU
> * @auto_boot: flag to indicate if remote processor should be auto-started
> * @autonomous: true if an external entity has booted the remote processor
> + * @deny_sysfs_ops: flag to not permit sysfs operations on state, firmware and recovery
> * @dump_segments: list of segments in the firmware
> * @nb_vdev: number of vdev currently handled by rproc
> * @char_dev: character device of the rproc
> @@ -545,6 +546,7 @@ struct rproc {
> bool has_iommu;
> bool auto_boot;
> bool autonomous;
> + bool deny_sysfs_ops;
> struct list_head dump_segments;
> int nb_vdev;
> u8 elf_class;
> --
> 2.28.0
>