Unverified Commit 3823119b authored by Ziqi Zhao's avatar Ziqi Zhao Committed by Maxime Ripard
Browse files

drm/crtc: Fix uninit-value bug in drm_mode_setcrtc 



The connector_set contains uninitialized values when allocated with
kmalloc_array. However, in the "out" branch, the logic assumes that any
element in connector_set would be equal to NULL if failed to
initialize, which causes the bug reported by Syzbot. The fix is to use
an extra variable to keep track of how many connectors are initialized
indeed, and use that variable to decrease any refcounts in the "out"
branch.

Reported-by: default avatar <syzbot+4fad2e57beb6397ab2fc@syzkaller.appspotmail.com>
Signed-off-by: default avatarZiqi Zhao <astrajoan@yahoo.com>
Reported-and-tested-by: default avatar <syzbot+4fad2e57beb6397ab2fc@syzkaller.appspotmail.com>
Tested-by: default avatarHarshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Link: https://lore.kernel.org/r/20230721161446.8602-1-astrajoan@yahoo.com


Signed-off-by: default avatarMaxime Ripard <mripard@kernel.org>
parent 5a6c9a05

drivers/gpu/drm/drm_crtc.c

+5 −4
Original line number Diff line number Diff line
@@ -715,8 +715,7 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data, 
	struct drm_mode_set set;

	uint32_t __user *set_connectors_ptr;

	struct drm_modeset_acquire_ctx ctx;

	int ret;

	int i;

	int ret, i, num_connectors;



	if (!drm_core_check_feature(dev, DRIVER_MODESET))

		return -EOPNOTSUPP;
@@ -851,6 +850,7 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data, 
			goto out;

		}



		num_connectors = 0;

		for (i = 0; i < crtc_req->count_connectors; i++) {

			connector_set[i] = NULL;

			set_connectors_ptr = (uint32_t __user *)(unsigned long)crtc_req->set_connectors_ptr;
@@ -871,6 +871,7 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data, 
					connector->name);



			connector_set[i] = connector;

			num_connectors++;

		}

	}
@@ -879,7 +880,7 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data, 
	set.y = crtc_req->y;

	set.mode = mode;

	set.connectors = connector_set;

	set.num_connectors = crtc_req->count_connectors;

	set.num_connectors = num_connectors;

	set.fb = fb;



	if (drm_drv_uses_atomic_modeset(dev))
@@ -892,7 +893,7 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data, 
		drm_framebuffer_put(fb);



	if (connector_set) {

		for (i = 0; i < crtc_req->count_connectors; i++) {

		for (i = 0; i < num_connectors; i++) {

			if (connector_set[i])

				drm_connector_put(connector_set[i]);

		}