diff mbox series

[5.9,65/74] drm/i915/gem: Serialise debugfs i915_gem_objects with ctx->mutex

Message ID 20201031113503.143529242@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH Oct. 31, 2020, 11:36 a.m. UTC 
From: Chris Wilson <chris@chris-wilson.co.uk>

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 <chris@chris-wilson.co.uk>
Cc: CQ Tang <cq.tang@intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
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 <rodrigo.vivi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/i915/i915_debugfs.c |    2 ++
 1 file changed, 2 insertions(+)
diff mbox series

Patch

--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -326,6 +326,7 @@  static void print_context_stats(struct s
 		}
 		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),
@@ -346,6 +347,7 @@  static void print_context_stats(struct s
 
 			print_file_stats(m, name, stats);
 		}
+		mutex_unlock(&ctx->mutex);
 
 		spin_lock(&i915->gem.contexts.lock);
 		list_safe_reset_next(ctx, cn, link);