On 28/03/2023 10:36, Min Li wrote:
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@xxxxxxxxx>
Fixes: f89823c21224 ("drm/i915/perf: Implement I915_PERF_ADD/REMOVE_CONFIG interface")
Cc: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
Cc: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.14+
---
drivers/gpu/drm/i915/i915_perf.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index 824a34ec0b83..93748ca2c5da 100644
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -4634,13 +4634,13 @@ 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);
LGTM.
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Umesh or Lionel could you please double check? I can merge if confirmed okay.
Regards,
Tvrtko
