commit b440396387418fe2feaacd41ca16080e7a8bc9ad upstream.
linereq_set_config() behaves badly when direction is not set.
The configuration validation is borrowed from linereq_create(), where,
to verify the intent of the user, the direction must be set to in order to
effect a change to the electrical configuration of a line. But, when
applied to reconfiguration, that validation does not allow for the unset
direction case, making it possible to clear flags set previously without
specifying the line direction.
Adding to the inconsistency, those changes are not immediately applied by
linereq_set_config(), but will take effect when the line value is next get
or set.
For example, by requesting a configuration with no flags set, an output
line with GPIO_V2_LINE_FLAG_ACTIVE_LOW and GPIO_V2_LINE_FLAG_OPEN_DRAIN
set could have those flags cleared, inverting the sense of the line and
changing the line drive to push-pull on the next line value set.
Skip the reconfiguration of lines for which the direction is not set, and
only reconfigure the lines for which direction is set.
Fixes: a54756cb24ea ("gpiolib: cdev: support GPIO_V2_LINE_SET_CONFIG_IOCTL")
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Link: https://lore.kernel.org/r/20240626052925.174272-3-warthog618@gmail.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 9919cce62f68e6ab68dc2a975b5dc670f8ca7d40 ]
linehandle_set_config() behaves badly when direction is not set.
The configuration validation is borrowed from linehandle_create(), where,
to verify the intent of the user, the direction must be set to in order
to effect a change to the electrical configuration of a line. But, when
applied to reconfiguration, that validation does not allow for the unset
direction case, making it possible to clear flags set previously without
specifying the line direction.
Adding to the inconsistency, those changes are not immediately applied by
linehandle_set_config(), but will take effect when the line value is next
get or set.
For example, by requesting a configuration with no flags set, an output
line with GPIOHANDLE_REQUEST_ACTIVE_LOW and GPIOHANDLE_REQUEST_OPEN_DRAIN
requested could have those flags cleared, inverting the sense of the line
and changing the line drive to push-pull on the next line value set.
Ensure the intent of the user by disallowing configurations which do not
have direction set, returning an error to userspace to indicate that the
configuration is invalid.
And, for clarity, use lflags, a local copy of gcnf.flags, throughout when
dealing with the requested flags, rather than a mixture of both.
Fixes: e588bb1eae31 ("gpio: add new SET_CONFIG ioctl() to gpio chardev")
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Link: https://lore.kernel.org/r/20240626052925.174272-2-warthog618@gmail.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
