@@ -762,10 +762,14 @@ static struct uprobe *hprobe_expire(struct hprobe *hprobe, bool get)
enum hprobe_state hstate;
/*
- * return_instance's hprobe is protected by RCU.
- * Underlying uprobe is itself protected from reuse by SRCU.
+ * Caller should guarantee that return_instance is not going to be
+ * freed from under us. This can be achieved either through holding
+ * rcu_read_lock() or by owning return_instance in the first place.
+ *
+ * Underlying uprobe is itself protected from reuse by SRCU, so ensure
+ * SRCU lock is held properly.
*/
- lockdep_assert(rcu_read_lock_held() && srcu_read_lock_held(&uretprobes_srcu));
+ lockdep_assert(srcu_read_lock_held(&uretprobes_srcu));
hstate = READ_ONCE(hprobe->state);
switch (hstate) {
hprobe_expire() is used to atomically switch pending uretprobe instance (struct return_instance) from being SRCU protected to be refcounted. This can be done from background timer thread, or synchronously within current thread when task is forked. In the former case, return_instance has to be protected through RCU read lock, and that's what hprobe_expire() used to check with lockdep_assert(rcu_read_lock_held()). But in the latter case (hprobe_expire() called from dup_utask()) there is no RCU lock being held, and it's both unnecessary and incovenient. Inconvenient due to the intervening memory allocations inside dup_return_instance()'s loop. Unnecessary because dup_utask() is called synchronously in current thread, and no uretprobe can run at that point, so return_instance can't be freed either. So drop rcu_read_lock_held() condition, and expand corresponding comment to explain necessary lifetime guarantees. lockdep_assert()-detected issue is a false positive. Fixes: dd1a7567784e ("uprobes: SRCU-protect uretprobe lifetime (with timeout)") Reported-by: Breno Leitao <leitao@debian.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> --- kernel/events/uprobes.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)