Commit eb4dedae authored by Chris Wilson's avatar Chris Wilson Committed by Joonas Lahtinen
Browse files

drm/i915/gem: Delay tracking the GEM context until it is registered 



Avoid exposing a partially constructed context by deferring the
list_add() from the initial construction to the end of registration.
Otherwise, if we peek into the list of contexts from inside debugfs, we
may see the partially constructed context and chase down some dangling
incomplete pointers.

Reported-by: default avatarCQ Tang <cq.tang@intel.com>
Fixes: 3aa9945a ("drm/i915: Separate GEM context construction and registration to userspace")
References: f6e8aa38 ("drm/i915: Report the number of closed vma held by each context in debugfs")
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: CQ Tang <cq.tang@intel.com>
Cc: <stable@vger.kernel.org> # v5.2+
Reviewed-by: default avatarMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200730092856.23615-1-chris@chris-wilson.co.uk


Signed-off-by: default avatarRodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
parent a30e4ec1

drivers/gpu/drm/i915/gem/i915_gem_context.c

+11 −5
Original line number Diff line number Diff line
@@ -713,6 +713,7 @@ __create_context(struct drm_i915_private *i915) 
	ctx->i915 = i915;

	ctx->sched.priority = I915_USER_PRIORITY(I915_PRIORITY_NORMAL);

	mutex_init(&ctx->mutex);

	INIT_LIST_HEAD(&ctx->link);



	spin_lock_init(&ctx->stale.lock);

	INIT_LIST_HEAD(&ctx->stale.engines);
@@ -740,10 +741,6 @@ __create_context(struct drm_i915_private *i915) 
	for (i = 0; i < ARRAY_SIZE(ctx->hang_timestamp); i++)

		ctx->hang_timestamp[i] = jiffies - CONTEXT_FAST_HANG_JIFFIES;



	spin_lock(&i915->gem.contexts.lock);

	list_add_tail(&ctx->link, &i915->gem.contexts.list);

	spin_unlock(&i915->gem.contexts.lock);



	return ctx;



err_free:
@@ -931,6 +928,7 @@ static int gem_context_register(struct i915_gem_context *ctx, 
				struct drm_i915_file_private *fpriv,

				u32 *id)

{

	struct drm_i915_private *i915 = ctx->i915;

	struct i915_address_space *vm;

	int ret;
@@ -949,8 +947,16 @@ static int gem_context_register(struct i915_gem_context *ctx, 
	/* And finally expose ourselves to userspace via the idr */

	ret = xa_alloc(&fpriv->context_xa, id, ctx, xa_limit_32b, GFP_KERNEL);

	if (ret)

		put_pid(fetch_and_zero(&ctx->pid));

		goto err_pid;



	spin_lock(&i915->gem.contexts.lock);

	list_add_tail(&ctx->link, &i915->gem.contexts.list);

	spin_unlock(&i915->gem.contexts.lock);



	return 0;



err_pid:

	put_pid(fetch_and_zero(&ctx->pid));

	return ret;

}