stm class: Fix unlocking braino in the error path

If an illegal attempt is made to unlink stm source device from an
stm device, the stm device's link spinlock mistakenly remains locked.
While this really shouldn't happen (there's a warning in place), the
locking should remain in order so that we can still recover from this
situation if it indeed does happen.

This patch unifies the unlocking in the exit path of
__stm_source_link_drop() to fix this.

Reported-by: Laurent Fert <laurent.fert@intel.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 4 deletions

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index 0db303b50e51..4a626d8990b2 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -816,10 +816,8 @@ static void __stm_source_link_drop(struct stm_source_device *src,
         spin_lock(&stm->link_lock);
         spin_lock(&src->link_lock);
         link = srcu_dereference_check(src->link, &stm_source_srcu, 1);
-        if (WARN_ON_ONCE(link != stm)) {
-                spin_unlock(&src->link_lock);
-                return;
-        }
+        if (WARN_ON_ONCE(link != stm))
+                goto unlock;
 
         stm_output_free(link, &src->output);
         list_del_init(&src->link_entry);
@@ -827,6 +825,7 @@ static void __stm_source_link_drop(struct stm_source_device *src,
         stm_put_device(link);
         rcu_assign_pointer(src->link, NULL);
 
+unlock:
         spin_unlock(&src->link_lock);
         spin_unlock(&stm->link_lock);
 }