The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e7d95527f27a6d9edcffbd74eee38e5cb6b91785 Mon Sep 17 00:00:00 2001

From: Chris Wilson chris@chris-wilson.co.uk Date: Thu, 30 Jul 2020 10:28:56 +0100 Subject: [PATCH] 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: CQ Tang cq.tang@intel.com Fixes: 3aa9945a528e ("drm/i915: Separate GEM context construction and registration to userspace") References: f6e8aa387171 ("drm/i915: Report the number of closed vma held by each context in debugfs") Signed-off-by: Chris 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: Mika Kuoppala mika.kuoppala@linux.intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20200730092856.23615-1-chris@c... Signed-off-by: Rodrigo Vivi rodrigo.vivi@intel.com Signed-off-by: Joonas Lahtinen joonas.lahtinen@linux.intel.com (cherry picked from commit eb4dedae920a07c485328af3da2202ec5184fb17) Signed-off-by: Jani Nikula jani.nikula@intel.com

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c index d0bdb6d447ed..efc4ba34c06e 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c @@ -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; }