From fad2083483bb7f743486199f90dc042939323453 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Sat, 1 Jul 2017 00:05:17 +0100
Subject: [PATCH] drm/i915: Fix use-after-free of context during free_contexts
Git-commit: fad2083483bb7f743486199f90dc042939323453
Patch-mainline: v4.14-rc1
References: FATE#322643 bsc#1055900

When iterating the list of contexts to free, we need to use a safe
iterator as we are freeing the link as we go. Pass an extra thick brown
paper bag.

Fixes: 5f09a9c8ab6b ("drm/i915: Allow contexts to be unreferenced locklessly")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170630230517.1938-1-chris@chris-wilson.co.uk
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/i915_gem_context.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -193,11 +193,11 @@ static void i915_gem_context_free(struct
 static void contexts_free(struct drm_i915_private *i915)
 {
 	struct llist_node *freed = llist_del_all(&i915->contexts.free_list);
-	struct i915_gem_context *ctx;
+	struct i915_gem_context *ctx, *cn;
 
 	lockdep_assert_held(&i915->drm.struct_mutex);
 
-	llist_for_each_entry(ctx, freed, free_link)
+	llist_for_each_entry_safe(ctx, cn, freed, free_link)
 		i915_gem_context_free(ctx);
 }