From 8f924c0a5665a74fc74ea50f71999914095aaf88 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 23 Jul 2020 18:21:19 +0100 Subject: [PATCH] drm/i915/gem: Serialise debugfs i915_gem_objects with ctx->mutex commit 4fe9af8e881d946bf60790eeb37a7c4f96e28382 upstream. Since the debugfs may peek into the GEM contexts as the corresponding client/fd is being closed, we may try and follow a dangling pointer. However, the context closure itself is serialised with the ctx->mutex, so if we hold that mutex as we inspect the state coupled in the context, we know the pointers within the context are stable and will remain valid as we inspect their tables. Signed-off-by: Chris Wilson Cc: CQ Tang Cc: Daniel Vetter Cc: stable@vger.kernel.org Reviewed-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20200723172119.17649-3-chris@chris-wilson.co.uk (cherry picked from commit 102f5aa491f262c818e607fc4fee08a724a76c69) Signed-off-by: Rodrigo Vivi Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/i915/i915_debugfs.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c index e7532e7d74e91..0e1f11669b072 100644 --- a/drivers/gpu/drm/i915/i915_debugfs.c +++ b/drivers/gpu/drm/i915/i915_debugfs.c @@ -323,6 +323,7 @@ static void print_context_stats(struct seq_file *m, } i915_gem_context_unlock_engines(ctx); + mutex_lock(&ctx->mutex); if (!IS_ERR_OR_NULL(ctx->file_priv)) { struct file_stats stats = { .vm = rcu_access_pointer(ctx->vm), @@ -343,6 +344,7 @@ static void print_context_stats(struct seq_file *m, print_file_stats(m, name, stats); } + mutex_unlock(&ctx->mutex); spin_lock(&i915->gem.contexts.lock); list_safe_reset_next(ctx, cn, link); -- 2.47.2