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SubjectRe: [PATCH] regmap: Disable debugfs when locking is disabled
2017-12-12 18:13 GMT+01:00 Mark Brown <broonie@kernel.org>:
> The recently added support for disabling the regmap internal locking left
> debugfs enabled for devices with the locking disabled. This is a problem
> since debugfs allows userspace to do things like initiate reads from the
> hardware which will use the scratch buffers protected by the regmap locking
> so could cause data corruption.
>
> For safety address this by just disabling debugfs for these devices. That
> is overly conservative since some of the debugfs files just read internal
> data structures but it's much simpler to implmement and less likely to
> lead to problems with tooling that works with debugfs.
>
> Reported-by: Lars-Peter Clausen <lars@metafoo.de>
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
>
> Compile tested only so far.
>
> drivers/base/regmap/internal.h | 8 ++++++++
> drivers/base/regmap/regmap-debugfs.c | 3 +++
> drivers/base/regmap/regmap.c | 1 +
> 3 files changed, 12 insertions(+)
>
> diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
> index 8641183cac2f..8d652023f8bd 100644
> --- a/drivers/base/regmap/internal.h
> +++ b/drivers/base/regmap/internal.h
> @@ -77,6 +77,7 @@ struct regmap {
> int async_ret;
>
> #ifdef CONFIG_DEBUG_FS
> + bool debugfs_disable;
> struct dentry *debugfs;
> const char *debugfs_name;
>
> @@ -215,10 +216,17 @@ struct regmap_field {
> extern void regmap_debugfs_initcall(void);
> extern void regmap_debugfs_init(struct regmap *map, const char *name);
> extern void regmap_debugfs_exit(struct regmap *map);
> +
> +static void regmap_debugfs_disable(struct regmap *map)
> +{
> + map->debugfs_disable = true;
> +}
> +
> #else
> static inline void regmap_debugfs_initcall(void) { }
> static inline void regmap_debugfs_init(struct regmap *map, const char *name) { }
> static inline void regmap_debugfs_exit(struct regmap *map) { }
> +static inline void regmap_debugfs_disable(struct regmap *map) { }
> #endif
>
> /* regcache core declarations */
> diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
> index 36ce3511c733..c8ecefd75d6f 100644
> --- a/drivers/base/regmap/regmap-debugfs.c
> +++ b/drivers/base/regmap/regmap-debugfs.c
> @@ -529,6 +529,9 @@ void regmap_debugfs_init(struct regmap *map, const char *name)
> struct regmap_range_node *range_node;
> const char *devname = "dummy";
>
> + if (map->debugfs_disable)
> + return;
> +

I would still add the dev_dbg() here like in my version, since someone
may start wondering why the debugfs files are not being creating for
certain regmaps.

Thanks,
Bartosz

> /* If we don't have the debugfs root yet, postpone init */
> if (!regmap_debugfs_root) {
> struct regmap_debugfs_node *node;
> diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
> index 1da2a9fc40b0..b884da59dd71 100644
> --- a/drivers/base/regmap/regmap.c
> +++ b/drivers/base/regmap/regmap.c
> @@ -674,6 +674,7 @@ struct regmap *__regmap_init(struct device *dev,
>
> if (config->disable_locking) {
> map->lock = map->unlock = regmap_lock_unlock_empty;
> + regmap_debugfs_disable(map);
> } else if (config->lock && config->unlock) {
> map->lock = config->lock;
> map->unlock = config->unlock;
> --
> 2.15.1
>

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