linux-kernel - [PATCH 4.14 31/70] drm/syncobj: Fix drm_syncobj_handle_to

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Date:   Mon, 12 Oct 2020 15:26:47 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Giuliano Procida <gprocida@...gle.com>
Subject: [PATCH 4.14 31/70] drm/syncobj: Fix drm_syncobj_handle_to_fd refcount leak

From: Giuliano Procida <gprocida@...gle.com>

Commit 5fb252cad61f20ae5d5a8b199f6cc4faf6f418e1, a cherry-pick of
upstream commit e7cdf5c82f1773c3386b93bbcf13b9bfff29fa31, introduced a
refcount imbalance and thus a struct drm_syncobj object leak which can
be triggered with DRM_IOCTL_SYNCOBJ_HANDLE_TO_FD.

The function drm_syncobj_handle_to_fd first calls drm_syncobj_find
which increments the refcount of the object on success. In all of the
drm_syncobj_handle_to_fd error paths, the refcount is decremented, but
in the success path the refcount should remain at +1 as the struct
drm_syncobj now belongs to the newly opened file. Instead, the
refcount was incremented again to +2.

Fixes: 5fb252cad61f ("drm/syncobj: Stop reusing the same struct file for all syncobj -> fd")
Signed-off-by: Giuliano Procida <gprocida@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/drm_syncobj.c |    1 -
 1 file changed, 1 deletion(-)

--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -355,7 +355,6 @@ static int drm_syncobj_handle_to_fd(stru
 		return PTR_ERR(file);
 	}

-	drm_syncobj_get(syncobj);
 	fd_install(fd, file);

 	*p_fd = fd;