| Message ID | 20241025171128.1226045-1-quic_mojha@quicinc.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] leds: class: Protect brightness_show() with led_cdev->led_access mutex | expand |
On Fri, Oct 25, 2024 at 10:12 AM Mukesh Ojha <quic_mojha@quicinc.com> wrote: > > There is NULL pointer issue observed if from Process A where hid device > being added which results in adding a led_cdev addition and later a > another call to access of led_cdev attribute from Process B can result > in NULL pointer issue. > > Use mutex led_cdev->led_access to protect access to led->cdev and its > attribute inside brightness_show() and max_brightness_show() and also > update the comment for mutex that it should be used to protect the led > class device fields. > > Process A Process B > > kthread+0x114 > worker_thread+0x244 > process_scheduled_works+0x248 > uhid_device_add_worker+0x24 > hid_add_device+0x120 > device_add+0x268 > bus_probe_device+0x94 > device_initial_probe+0x14 > __device_attach+0xfc > bus_for_each_drv+0x10c > __device_attach_driver+0x14c > driver_probe_device+0x3c > __driver_probe_device+0xa0 > really_probe+0x190 > hid_device_probe+0x130 > ps_probe+0x990 > ps_led_register+0x94 > devm_led_classdev_register_ext+0x58 > led_classdev_register_ext+0x1f8 > device_create_with_groups+0x48 > device_create_groups_vargs+0xc8 > device_add+0x244 > kobject_uevent+0x14 > kobject_uevent_env[jt]+0x224 > mutex_unlock[jt]+0xc4 > __mutex_unlock_slowpath+0xd4 > wake_up_q+0x70 > try_to_wake_up[jt]+0x48c > preempt_schedule_common+0x28 > __schedule+0x628 > __switch_to+0x174 > el0t_64_sync+0x1a8/0x1ac > el0t_64_sync_handler+0x68/0xbc > el0_svc+0x38/0x68 > do_el0_svc+0x1c/0x28 > el0_svc_common+0x80/0xe0 > invoke_syscall+0x58/0x114 > __arm64_sys_read+0x1c/0x2c > ksys_read+0x78/0xe8 > vfs_read+0x1e0/0x2c8 > kernfs_fop_read_iter+0x68/0x1b4 > seq_read_iter+0x158/0x4ec > kernfs_seq_show+0x44/0x54 > sysfs_kf_seq_show+0xb4/0x130 > dev_attr_show+0x38/0x74 > brightness_show+0x20/0x4c > dualshock4_led_get_brightness+0xc/0x74 > > [ 3313.874295][ T4013] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000060 > [ 3313.874301][ T4013] Mem abort info: > [ 3313.874303][ T4013] ESR = 0x0000000096000006 > [ 3313.874305][ T4013] EC = 0x25: DABT (current EL), IL = 32 bits > [ 3313.874307][ T4013] SET = 0, FnV = 0 > [ 3313.874309][ T4013] EA = 0, S1PTW = 0 > [ 3313.874311][ T4013] FSC = 0x06: level 2 translation fault > [ 3313.874313][ T4013] Data abort info: > [ 3313.874314][ T4013] ISV = 0, ISS = 0x00000006, ISS2 = 0x00000000 > [ 3313.874316][ T4013] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 > [ 3313.874318][ T4013] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 > [ 3313.874320][ T4013] user pgtable: 4k pages, 39-bit VAs, pgdp=00000008f2b0a000 > .. > > [ 3313.874332][ T4013] Dumping ftrace buffer: > [ 3313.874334][ T4013] (ftrace buffer empty) > .. > .. > [ dd3313.874639][ T4013] CPU: 6 PID: 4013 Comm: InputReader > [ 3313.874648][ T4013] pc : dualshock4_led_get_brightness+0xc/0x74 > [ 3313.874653][ T4013] lr : led_update_brightness+0x38/0x60 > [ 3313.874656][ T4013] sp : ffffffc0b910bbd0 > .. > .. > [ 3313.874685][ T4013] Call trace: > [ 3313.874687][ T4013] dualshock4_led_get_brightness+0xc/0x74 > [ 3313.874690][ T4013] brightness_show+0x20/0x4c > [ 3313.874692][ T4013] dev_attr_show+0x38/0x74 > [ 3313.874696][ T4013] sysfs_kf_seq_show+0xb4/0x130 > [ 3313.874700][ T4013] kernfs_seq_show+0x44/0x54 > [ 3313.874703][ T4013] seq_read_iter+0x158/0x4ec > [ 3313.874705][ T4013] kernfs_fop_read_iter+0x68/0x1b4 > [ 3313.874708][ T4013] vfs_read+0x1e0/0x2c8 > [ 3313.874711][ T4013] ksys_read+0x78/0xe8 > [ 3313.874714][ T4013] __arm64_sys_read+0x1c/0x2c > [ 3313.874718][ T4013] invoke_syscall+0x58/0x114 > [ 3313.874721][ T4013] el0_svc_common+0x80/0xe0 > [ 3313.874724][ T4013] do_el0_svc+0x1c/0x28 > [ 3313.874727][ T4013] el0_svc+0x38/0x68 > [ 3313.874730][ T4013] el0t_64_sync_handler+0x68/0xbc > [ 3313.874732][ T4013] el0t_64_sync+0x1a8/0x1ac > > Signed-off-by: Mukesh Ojha <quic_mojha@quicinc.com> Reviewed-by: anish kumar <yesanishhere@gmail.com> > --- > Changes in v2: > - Updated the comment for led_access mutex lock. > - Also added mutex protection for max_brightness_show(). > > drivers/leds/led-class.c | 14 +++++++++++--- > include/linux/leds.h | 2 +- > 2 files changed, 12 insertions(+), 4 deletions(-) > > diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c > index 06b97fd49ad9..f69f4e928d61 100644 > --- a/drivers/leds/led-class.c > +++ b/drivers/leds/led-class.c > @@ -29,11 +29,14 @@ static ssize_t brightness_show(struct device *dev, > struct device_attribute *attr, char *buf) > { > struct led_classdev *led_cdev = dev_get_drvdata(dev); > + unsigned int brightness; > > - /* no lock needed for this */ > + mutex_lock(&led_cdev->led_access); > led_update_brightness(led_cdev); > + brightness = led_cdev->brightness; > + mutex_unlock(&led_cdev->led_access); > > - return sprintf(buf, "%u\n", led_cdev->brightness); > + return sprintf(buf, "%u\n", brightness); > } > > static ssize_t brightness_store(struct device *dev, > @@ -70,8 +73,13 @@ static ssize_t max_brightness_show(struct device *dev, > struct device_attribute *attr, char *buf) > { > struct led_classdev *led_cdev = dev_get_drvdata(dev); > + unsigned int max_brightness; > + > + mutex_lock(&led_cdev->led_access); > + max_brightness = led_cdev->max_brightness; > + mutex_unlock(&led_cdev->led_access); > > - return sprintf(buf, "%u\n", led_cdev->max_brightness); > + return sprintf(buf, "%u\n", max_brightness); > } > static DEVICE_ATTR_RO(max_brightness); > > diff --git a/include/linux/leds.h b/include/linux/leds.h > index e5968c3ed4ae..3524634fcc47 100644 > --- a/include/linux/leds.h > +++ b/include/linux/leds.h > @@ -238,7 +238,7 @@ struct led_classdev { > struct kernfs_node *brightness_hw_changed_kn; > #endif > > - /* Ensures consistent access to the LED Flash Class device */ > + /* Ensures consistent access to the LED Class device */ > struct mutex led_access; > }; > > -- > 2.34.1 > >
Hi Mukesh, On 10/25/24 19:11, Mukesh Ojha wrote: > There is NULL pointer issue observed if from Process A where hid device > being added which results in adding a led_cdev addition and later a > another call to access of led_cdev attribute from Process B can result > in NULL pointer issue. > > Use mutex led_cdev->led_access to protect access to led->cdev and its > attribute inside brightness_show() and max_brightness_show() and also > update the comment for mutex that it should be used to protect the led > class device fields. > > Process A Process B > > kthread+0x114 > worker_thread+0x244 > process_scheduled_works+0x248 > uhid_device_add_worker+0x24 > hid_add_device+0x120 > device_add+0x268 > bus_probe_device+0x94 > device_initial_probe+0x14 > __device_attach+0xfc > bus_for_each_drv+0x10c > __device_attach_driver+0x14c > driver_probe_device+0x3c > __driver_probe_device+0xa0 > really_probe+0x190 > hid_device_probe+0x130 > ps_probe+0x990 > ps_led_register+0x94 > devm_led_classdev_register_ext+0x58 > led_classdev_register_ext+0x1f8 > device_create_with_groups+0x48 > device_create_groups_vargs+0xc8 > device_add+0x244 > kobject_uevent+0x14 > kobject_uevent_env[jt]+0x224 > mutex_unlock[jt]+0xc4 > __mutex_unlock_slowpath+0xd4 > wake_up_q+0x70 > try_to_wake_up[jt]+0x48c > preempt_schedule_common+0x28 > __schedule+0x628 > __switch_to+0x174 > el0t_64_sync+0x1a8/0x1ac > el0t_64_sync_handler+0x68/0xbc > el0_svc+0x38/0x68 > do_el0_svc+0x1c/0x28 > el0_svc_common+0x80/0xe0 > invoke_syscall+0x58/0x114 > __arm64_sys_read+0x1c/0x2c > ksys_read+0x78/0xe8 > vfs_read+0x1e0/0x2c8 > kernfs_fop_read_iter+0x68/0x1b4 > seq_read_iter+0x158/0x4ec > kernfs_seq_show+0x44/0x54 > sysfs_kf_seq_show+0xb4/0x130 > dev_attr_show+0x38/0x74 > brightness_show+0x20/0x4c > dualshock4_led_get_brightness+0xc/0x74 > > [ 3313.874295][ T4013] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000060 > [ 3313.874301][ T4013] Mem abort info: > [ 3313.874303][ T4013] ESR = 0x0000000096000006 > [ 3313.874305][ T4013] EC = 0x25: DABT (current EL), IL = 32 bits > [ 3313.874307][ T4013] SET = 0, FnV = 0 > [ 3313.874309][ T4013] EA = 0, S1PTW = 0 > [ 3313.874311][ T4013] FSC = 0x06: level 2 translation fault > [ 3313.874313][ T4013] Data abort info: > [ 3313.874314][ T4013] ISV = 0, ISS = 0x00000006, ISS2 = 0x00000000 > [ 3313.874316][ T4013] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 > [ 3313.874318][ T4013] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 > [ 3313.874320][ T4013] user pgtable: 4k pages, 39-bit VAs, pgdp=00000008f2b0a000 > .. > > [ 3313.874332][ T4013] Dumping ftrace buffer: > [ 3313.874334][ T4013] (ftrace buffer empty) > .. > .. > [ dd3313.874639][ T4013] CPU: 6 PID: 4013 Comm: InputReader > [ 3313.874648][ T4013] pc : dualshock4_led_get_brightness+0xc/0x74 > [ 3313.874653][ T4013] lr : led_update_brightness+0x38/0x60 > [ 3313.874656][ T4013] sp : ffffffc0b910bbd0 > .. > .. > [ 3313.874685][ T4013] Call trace: > [ 3313.874687][ T4013] dualshock4_led_get_brightness+0xc/0x74 > [ 3313.874690][ T4013] brightness_show+0x20/0x4c > [ 3313.874692][ T4013] dev_attr_show+0x38/0x74 > [ 3313.874696][ T4013] sysfs_kf_seq_show+0xb4/0x130 > [ 3313.874700][ T4013] kernfs_seq_show+0x44/0x54 > [ 3313.874703][ T4013] seq_read_iter+0x158/0x4ec > [ 3313.874705][ T4013] kernfs_fop_read_iter+0x68/0x1b4 > [ 3313.874708][ T4013] vfs_read+0x1e0/0x2c8 > [ 3313.874711][ T4013] ksys_read+0x78/0xe8 > [ 3313.874714][ T4013] __arm64_sys_read+0x1c/0x2c > [ 3313.874718][ T4013] invoke_syscall+0x58/0x114 > [ 3313.874721][ T4013] el0_svc_common+0x80/0xe0 > [ 3313.874724][ T4013] do_el0_svc+0x1c/0x28 > [ 3313.874727][ T4013] el0_svc+0x38/0x68 > [ 3313.874730][ T4013] el0t_64_sync_handler+0x68/0xbc > [ 3313.874732][ T4013] el0t_64_sync+0x1a8/0x1ac > > Signed-off-by: Mukesh Ojha <quic_mojha@quicinc.com> > --- > Changes in v2: > - Updated the comment for led_access mutex lock. > - Also added mutex protection for max_brightness_show(). > > drivers/leds/led-class.c | 14 +++++++++++--- > include/linux/leds.h | 2 +- > 2 files changed, 12 insertions(+), 4 deletions(-) > > diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c > index 06b97fd49ad9..f69f4e928d61 100644 > --- a/drivers/leds/led-class.c > +++ b/drivers/leds/led-class.c > @@ -29,11 +29,14 @@ static ssize_t brightness_show(struct device *dev, > struct device_attribute *attr, char *buf) > { > struct led_classdev *led_cdev = dev_get_drvdata(dev); > + unsigned int brightness; > > - /* no lock needed for this */ > + mutex_lock(&led_cdev->led_access); > led_update_brightness(led_cdev); > + brightness = led_cdev->brightness; > + mutex_unlock(&led_cdev->led_access); > > - return sprintf(buf, "%u\n", led_cdev->brightness); > + return sprintf(buf, "%u\n", brightness); > } > > static ssize_t brightness_store(struct device *dev, > @@ -70,8 +73,13 @@ static ssize_t max_brightness_show(struct device *dev, > struct device_attribute *attr, char *buf) > { > struct led_classdev *led_cdev = dev_get_drvdata(dev); > + unsigned int max_brightness; > + > + mutex_lock(&led_cdev->led_access); > + max_brightness = led_cdev->max_brightness; > + mutex_unlock(&led_cdev->led_access); > > - return sprintf(buf, "%u\n", led_cdev->max_brightness); > + return sprintf(buf, "%u\n", max_brightness); > } > static DEVICE_ATTR_RO(max_brightness); > > diff --git a/include/linux/leds.h b/include/linux/leds.h > index e5968c3ed4ae..3524634fcc47 100644 > --- a/include/linux/leds.h > +++ b/include/linux/leds.h > @@ -238,7 +238,7 @@ struct led_classdev { > struct kernfs_node *brightness_hw_changed_kn; > #endif > > - /* Ensures consistent access to the LED Flash Class device */ > + /* Ensures consistent access to the LED Class device */ Nit: It was improper in the original comment as well: s/Class/class/ > struct mutex led_access; > }; > Reviewed-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
On Sun, 27 Oct 2024, Jacek Anaszewski wrote: > Hi Mukesh, > > On 10/25/24 19:11, Mukesh Ojha wrote: > > There is NULL pointer issue observed if from Process A where hid device > > being added which results in adding a led_cdev addition and later a > > another call to access of led_cdev attribute from Process B can result > > in NULL pointer issue. > > > > Use mutex led_cdev->led_access to protect access to led->cdev and its > > attribute inside brightness_show() and max_brightness_show() and also > > update the comment for mutex that it should be used to protect the led > > class device fields. [...] > > Signed-off-by: Mukesh Ojha <quic_mojha@quicinc.com> > > --- > > Changes in v2: > > - Updated the comment for led_access mutex lock. > > - Also added mutex protection for max_brightness_show(). > > > > drivers/leds/led-class.c | 14 +++++++++++--- > > include/linux/leds.h | 2 +- > > 2 files changed, 12 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c > > index 06b97fd49ad9..f69f4e928d61 100644 > > --- a/drivers/leds/led-class.c > > +++ b/drivers/leds/led-class.c > > @@ -29,11 +29,14 @@ static ssize_t brightness_show(struct device *dev, > > struct device_attribute *attr, char *buf) > > { > > struct led_classdev *led_cdev = dev_get_drvdata(dev); > > + unsigned int brightness; > > - /* no lock needed for this */ > > + mutex_lock(&led_cdev->led_access); > > led_update_brightness(led_cdev); > > + brightness = led_cdev->brightness; > > + mutex_unlock(&led_cdev->led_access); > > - return sprintf(buf, "%u\n", led_cdev->brightness); > > + return sprintf(buf, "%u\n", brightness); > > } > > static ssize_t brightness_store(struct device *dev, > > @@ -70,8 +73,13 @@ static ssize_t max_brightness_show(struct device *dev, > > struct device_attribute *attr, char *buf) > > { > > struct led_classdev *led_cdev = dev_get_drvdata(dev); > > + unsigned int max_brightness; > > + > > + mutex_lock(&led_cdev->led_access); > > + max_brightness = led_cdev->max_brightness; > > + mutex_unlock(&led_cdev->led_access); > > - return sprintf(buf, "%u\n", led_cdev->max_brightness); > > + return sprintf(buf, "%u\n", max_brightness); > > } > > static DEVICE_ATTR_RO(max_brightness); > > diff --git a/include/linux/leds.h b/include/linux/leds.h > > index e5968c3ed4ae..3524634fcc47 100644 > > --- a/include/linux/leds.h > > +++ b/include/linux/leds.h > > @@ -238,7 +238,7 @@ struct led_classdev { > > struct kernfs_node *brightness_hw_changed_kn; > > #endif > > - /* Ensures consistent access to the LED Flash Class device */ > > + /* Ensures consistent access to the LED Class device */ > > Nit: It was improper in the original comment as well: > > s/Class/class/ Some things can't be unseen. Please submit v3.
diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c index 06b97fd49ad9..f69f4e928d61 100644 --- a/drivers/leds/led-class.c +++ b/drivers/leds/led-class.c @@ -29,11 +29,14 @@ static ssize_t brightness_show(struct device *dev, struct device_attribute *attr, char *buf) { struct led_classdev *led_cdev = dev_get_drvdata(dev); + unsigned int brightness; - /* no lock needed for this */ + mutex_lock(&led_cdev->led_access); led_update_brightness(led_cdev); + brightness = led_cdev->brightness; + mutex_unlock(&led_cdev->led_access); - return sprintf(buf, "%u\n", led_cdev->brightness); + return sprintf(buf, "%u\n", brightness); } static ssize_t brightness_store(struct device *dev, @@ -70,8 +73,13 @@ static ssize_t max_brightness_show(struct device *dev, struct device_attribute *attr, char *buf) { struct led_classdev *led_cdev = dev_get_drvdata(dev); + unsigned int max_brightness; + + mutex_lock(&led_cdev->led_access); + max_brightness = led_cdev->max_brightness; + mutex_unlock(&led_cdev->led_access); - return sprintf(buf, "%u\n", led_cdev->max_brightness); + return sprintf(buf, "%u\n", max_brightness); } static DEVICE_ATTR_RO(max_brightness); diff --git a/include/linux/leds.h b/include/linux/leds.h index e5968c3ed4ae..3524634fcc47 100644 --- a/include/linux/leds.h +++ b/include/linux/leds.h @@ -238,7 +238,7 @@ struct led_classdev { struct kernfs_node *brightness_hw_changed_kn; #endif - /* Ensures consistent access to the LED Flash Class device */ + /* Ensures consistent access to the LED Class device */ struct mutex led_access; };
There is NULL pointer issue observed if from Process A where hid device being added which results in adding a led_cdev addition and later a another call to access of led_cdev attribute from Process B can result in NULL pointer issue. Use mutex led_cdev->led_access to protect access to led->cdev and its attribute inside brightness_show() and max_brightness_show() and also update the comment for mutex that it should be used to protect the led class device fields. Process A Process B kthread+0x114 worker_thread+0x244 process_scheduled_works+0x248 uhid_device_add_worker+0x24 hid_add_device+0x120 device_add+0x268 bus_probe_device+0x94 device_initial_probe+0x14 __device_attach+0xfc bus_for_each_drv+0x10c __device_attach_driver+0x14c driver_probe_device+0x3c __driver_probe_device+0xa0 really_probe+0x190 hid_device_probe+0x130 ps_probe+0x990 ps_led_register+0x94 devm_led_classdev_register_ext+0x58 led_classdev_register_ext+0x1f8 device_create_with_groups+0x48 device_create_groups_vargs+0xc8 device_add+0x244 kobject_uevent+0x14 kobject_uevent_env[jt]+0x224 mutex_unlock[jt]+0xc4 __mutex_unlock_slowpath+0xd4 wake_up_q+0x70 try_to_wake_up[jt]+0x48c preempt_schedule_common+0x28 __schedule+0x628 __switch_to+0x174 el0t_64_sync+0x1a8/0x1ac el0t_64_sync_handler+0x68/0xbc el0_svc+0x38/0x68 do_el0_svc+0x1c/0x28 el0_svc_common+0x80/0xe0 invoke_syscall+0x58/0x114 __arm64_sys_read+0x1c/0x2c ksys_read+0x78/0xe8 vfs_read+0x1e0/0x2c8 kernfs_fop_read_iter+0x68/0x1b4 seq_read_iter+0x158/0x4ec kernfs_seq_show+0x44/0x54 sysfs_kf_seq_show+0xb4/0x130 dev_attr_show+0x38/0x74 brightness_show+0x20/0x4c dualshock4_led_get_brightness+0xc/0x74 [ 3313.874295][ T4013] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000060 [ 3313.874301][ T4013] Mem abort info: [ 3313.874303][ T4013] ESR = 0x0000000096000006 [ 3313.874305][ T4013] EC = 0x25: DABT (current EL), IL = 32 bits [ 3313.874307][ T4013] SET = 0, FnV = 0 [ 3313.874309][ T4013] EA = 0, S1PTW = 0 [ 3313.874311][ T4013] FSC = 0x06: level 2 translation fault [ 3313.874313][ T4013] Data abort info: [ 3313.874314][ T4013] ISV = 0, ISS = 0x00000006, ISS2 = 0x00000000 [ 3313.874316][ T4013] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 [ 3313.874318][ T4013] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [ 3313.874320][ T4013] user pgtable: 4k pages, 39-bit VAs, pgdp=00000008f2b0a000 .. [ 3313.874332][ T4013] Dumping ftrace buffer: [ 3313.874334][ T4013] (ftrace buffer empty) .. .. [ dd3313.874639][ T4013] CPU: 6 PID: 4013 Comm: InputReader [ 3313.874648][ T4013] pc : dualshock4_led_get_brightness+0xc/0x74 [ 3313.874653][ T4013] lr : led_update_brightness+0x38/0x60 [ 3313.874656][ T4013] sp : ffffffc0b910bbd0 .. .. [ 3313.874685][ T4013] Call trace: [ 3313.874687][ T4013] dualshock4_led_get_brightness+0xc/0x74 [ 3313.874690][ T4013] brightness_show+0x20/0x4c [ 3313.874692][ T4013] dev_attr_show+0x38/0x74 [ 3313.874696][ T4013] sysfs_kf_seq_show+0xb4/0x130 [ 3313.874700][ T4013] kernfs_seq_show+0x44/0x54 [ 3313.874703][ T4013] seq_read_iter+0x158/0x4ec [ 3313.874705][ T4013] kernfs_fop_read_iter+0x68/0x1b4 [ 3313.874708][ T4013] vfs_read+0x1e0/0x2c8 [ 3313.874711][ T4013] ksys_read+0x78/0xe8 [ 3313.874714][ T4013] __arm64_sys_read+0x1c/0x2c [ 3313.874718][ T4013] invoke_syscall+0x58/0x114 [ 3313.874721][ T4013] el0_svc_common+0x80/0xe0 [ 3313.874724][ T4013] do_el0_svc+0x1c/0x28 [ 3313.874727][ T4013] el0_svc+0x38/0x68 [ 3313.874730][ T4013] el0t_64_sync_handler+0x68/0xbc [ 3313.874732][ T4013] el0t_64_sync+0x1a8/0x1ac Signed-off-by: Mukesh Ojha <quic_mojha@quicinc.com> --- Changes in v2: - Updated the comment for led_access mutex lock. - Also added mutex protection for max_brightness_show(). drivers/leds/led-class.c | 14 +++++++++++--- include/linux/leds.h | 2 +- 2 files changed, 12 insertions(+), 4 deletions(-)