linux-kernel - [PATCH v2 1/2] drm/shmem-helper: Remove errant put in error path

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Date:   Wed, 30 Nov 2022 10:57:47 -0800
From:   Rob Clark <robdclark@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Daniel Vetter <daniel@...ll.ch>,
        Rob Clark <robdclark@...omium.org>,
        syzbot+c8ae65286134dd1b800d@...kaller.appspotmail.com,
        stable@...r.kernel.org, Daniel Vetter <daniel.vetter@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Eric Anholt <eric@...olt.net>, Rob Herring <robh@...nel.org>,
        Noralf Trønnes <noralf@...nnes.org>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2 1/2] drm/shmem-helper: Remove errant put in error path

From: Rob Clark <robdclark@...omium.org>

drm_gem_shmem_mmap() doesn't own this reference, resulting in the GEM
object getting prematurely freed leading to a later use-after-free.

Link: https://syzkaller.appspot.com/bug?extid=c8ae65286134dd1b800d
Reported-by: syzbot+c8ae65286134dd1b800d@...kaller.appspotmail.com
Fixes: 2194a63a818d ("drm: Add library for shmem backed GEM objects")
Cc: stable@...r.kernel.org
Signed-off-by: Rob Clark <robdclark@...omium.org>
Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 35138f8a375c..3b7b71391a4c 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -622,10 +622,8 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct
 	}
 
 	ret = drm_gem_shmem_get_pages(shmem);
-	if (ret) {
-		drm_gem_vm_close(vma);
+	if (ret)
 		return ret;
-	}
 
 	vma->vm_flags |= VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
 	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
-- 
2.38.1