drm/panthor: Restrict high priorities on group_create

We were allowing any users to create a high priority group without any
permission checks. As a result, this was allowing possible denial of
service.

We now only allow the DRM master or users with the CAP_SYS_NICE
capability to set higher priorities than PANTHOR_GROUP_PRIORITY_MEDIUM.

As the sole user of that uAPI lives in Mesa and hardcode a value of
MEDIUM [1], this should be safe to do.

Additionally, as those checks are performed at the ioctl level,
panthor_group_create now only check for priority level validity.

[1]https://gitlab.freedesktop.org/mesa/mesa/-/blob/f390835074bdf162a63deb0311d1a6de527f9f89/src/gallium/drivers/panfrost/pan_csf.c#L1038

Signed-off-by: Mary Guillemard <mary.guillemard@collabora.com>
Fixes: de8548813824 ("drm/panthor: Add the scheduler logical block")
Cc: stable@vger.kernel.org
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240903144955.144278-2-mary.guillemard@collabora.com

diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
index b5e7b919f241e4b3010c3953c9ecdee5086cb770..34182f67136c175b0c2f8bd36eed0e74b20257ac 100644 (file)
--- a/drivers/gpu/drm/panthor/panthor_drv.c
+++ b/drivers/gpu/drm/panthor/panthor_drv.c
@@ -10,6 +10,7 @@
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 
+#include <drm/drm_auth.h>
 #include <drm/drm_debugfs.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_exec.h>
@@ -996,6 +997,24 @@ static int panthor_ioctl_group_destroy(struct drm_device *ddev, void *data,
        return panthor_group_destroy(pfile, args->group_handle);
 }
 
+static int group_priority_permit(struct drm_file *file,
+                                u8 priority)
+{
+       /* Ensure that priority is valid */
+       if (priority > PANTHOR_GROUP_PRIORITY_HIGH)
+               return -EINVAL;
+
+       /* Medium priority and below are always allowed */
+       if (priority <= PANTHOR_GROUP_PRIORITY_MEDIUM)
+               return 0;
+
+       /* Higher priorities require CAP_SYS_NICE or DRM_MASTER */
+       if (capable(CAP_SYS_NICE) || drm_is_current_master(file))
+               return 0;
+
+       return -EACCES;
+}
+
 static int panthor_ioctl_group_create(struct drm_device *ddev, void *data,
                                      struct drm_file *file)
 {
@@ -1011,6 +1030,10 @@ static int panthor_ioctl_group_create(struct drm_device *ddev, void *data,
        if (ret)
                return ret;
 
+       ret = group_priority_permit(file, args->priority);
+       if (ret)
+               return ret;
+
        ret = panthor_group_create(pfile, args, queue_args);
        if (ret >= 0) {
                args->group_handle = ret;

diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
index 463bcd3cf00f35b87d0d9a17c798f05f66a54e50..12b272a912f8611661c5f11b6368a3c68cabc879 100644 (file)
--- a/drivers/gpu/drm/panthor/panthor_sched.c
+++ b/drivers/gpu/drm/panthor/panthor_sched.c
@@ -3092,7 +3092,7 @@ int panthor_group_create(struct panthor_file *pfile,
        if (group_args->pad)
                return -EINVAL;
 
-       if (group_args->priority > PANTHOR_CSG_PRIORITY_HIGH)
+       if (group_args->priority >= PANTHOR_CSG_PRIORITY_COUNT)
                return -EINVAL;
 
        if ((group_args->compute_core_mask & ~ptdev->gpu_info.shader_present) ||

diff --git a/include/uapi/drm/panthor_drm.h b/include/uapi/drm/panthor_drm.h
index 926b1deb11166429d6a3497a1d0bac6f9cd38f5d..e23a7f9b0eacd1f5795ca20529a2137eba1e5b60 100644 (file)
--- a/include/uapi/drm/panthor_drm.h
+++ b/include/uapi/drm/panthor_drm.h
@@ -692,7 +692,11 @@ enum drm_panthor_group_priority {
        /** @PANTHOR_GROUP_PRIORITY_MEDIUM: Medium priority group. */
        PANTHOR_GROUP_PRIORITY_MEDIUM,
 
-       /** @PANTHOR_GROUP_PRIORITY_HIGH: High priority group. */
+       /**
+        * @PANTHOR_GROUP_PRIORITY_HIGH: High priority group.
+        *
+        * Requires CAP_SYS_NICE or DRM_MASTER.
+        */
        PANTHOR_GROUP_PRIORITY_HIGH,
 };