From: Min Li <lm0963hack@gmail.com>
Date: Tue, 28 Mar 2023 09:36:27 +0000 (+0800)
Subject: drm/i915: fix race condition UAF in i915_perf_add_config_ioctl
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=dc30c011469165d57af9adac5baff7d767d20e5c;p=linux.git

drm/i915: fix race condition UAF in i915_perf_add_config_ioctl

Userspace can guess the id value and try to race oa_config object creation
with config remove, resulting in a use-after-free if we dereference the
object after unlocking the metrics_lock.  For that reason, unlocking the
metrics_lock must be done after we are done dereferencing the object.

Signed-off-by: Min Li <lm0963hack@gmail.com>
Fixes: f89823c21224 ("drm/i915/perf: Implement I915_PERF_ADD/REMOVE_CONFIG interface")
Cc: <stable@vger.kernel.org> # v4.14+
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230328093627.5067-1-lm0963hack@gmail.com
[tursulin: Manually added stable tag.]
(cherry picked from commit 49f6f6483b652108bcb73accd0204a464b922395)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---

diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index 283a4a3c6862f..0040749363001 100644
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -4638,13 +4638,13 @@ int i915_perf_add_config_ioctl(struct drm_device *dev, void *data,
 		err = oa_config->id;
 		goto sysfs_err;
 	}
-
-	mutex_unlock(&perf->metrics_lock);
+	id = oa_config->id;
 
 	drm_dbg(&perf->i915->drm,
 		"Added config %s id=%i\n", oa_config->uuid, oa_config->id);
+	mutex_unlock(&perf->metrics_lock);
 
-	return oa_config->id;
+	return id;
 
 sysfs_err:
 	mutex_unlock(&perf->metrics_lock);