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From: Kees Cook <keescook@chromium.org>
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Subject: [PATCH 3/5] drm/i915: Do not directly manipulate file->f_count
Date: Thu,  2 May 2024 15:33:38 -0700
Message-Id: <20240502223341.1835070-3-keescook@chromium.org>
In-Reply-To: <20240502222252.work.690-kees@kernel.org>
References: <20240502222252.work.690-kees@kernel.org>
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The correct helper for taking an f_count reference is get_file(). Use it
and check results.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tursulin@ursulin.net>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Matt Atwood <matthew.s.atwood@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Nirmoy Das <nirmoy.das@intel.com>
Cc: Jonathan Cavitt <jonathan.cavitt@intel.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
---
 drivers/gpu/drm/i915/gt/shmem_utils.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/shmem_utils.c b/drivers/gpu/drm/i915/gt/shmem_utils.c
index bccc3a1200bc..dc25e6dc884b 100644
--- a/drivers/gpu/drm/i915/gt/shmem_utils.c
+++ b/drivers/gpu/drm/i915/gt/shmem_utils.c
@@ -38,8 +38,9 @@ struct file *shmem_create_from_object(struct drm_i915_gem_object *obj)
 	void *ptr;
 
 	if (i915_gem_object_is_shmem(obj)) {
-		file = obj->base.filp;
-		atomic_long_inc(&file->f_count);
+		file = get_file(obj->base.filp);
+		if (!file)
+			return ERR_PTR(-ESRCH);
 		return file;
 	}
 
-- 
2.34.1