From: Masami Hiramatsu (Google) <[email protected]>
find_active_uprobe_speculative() is called from find_active_uprobe_rcu(),
which is invoked by handle_swbp() and handle_syscall_uprobe().
Both callers already hold RCU Tasks Trace (via rcu_read_lock_trace() or
guard(rcu_tasks_trace)()).
Calling guard(rcu)() inside find_active_uprobe_speculative() is redundant
because the caller already guarantees RCU Tasks Trace protection.
Furthermore, standard RCU (rcu_read_lock()) does not protect uprobes_tree
against asynchronous uprobe destruction (call_rcu_tasks_trace()).
Remove the redundant guard(rcu)() from find_active_uprobe_speculative() and
replace it with lockdep_assert(rcu_read_lock_trace_held()) and a comment
documenting that callers must hold RCU Tasks Trace protection, matching the
convention used by find_active_uprobe_rcu() and find_uprobe_rcu().
Fixes: e0925f2dc4de ("uprobes: add speculative lockless VMA-to-inode-to-uprobe
resolution")
Assisted-by: Antigravity:gemini-3.6-flash
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
---
kernel/events/uprobes.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 4084e926e284..b4e253d43b30 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -2424,6 +2424,7 @@ static int is_trap_at_addr(struct mm_struct *mm, unsigned
long vaddr)
return is_trap_insn(&opcode);
}
+/* assumes being inside RCU Tasks Trace protected region */
static struct uprobe *find_active_uprobe_speculative(unsigned long bp_vaddr)
{
struct mm_struct *mm = current->mm;
@@ -2433,7 +2434,7 @@ static struct uprobe
*find_active_uprobe_speculative(unsigned long bp_vaddr)
loff_t offset;
unsigned int seq;
- guard(rcu)();
+ lockdep_assert(rcu_read_lock_trace_held());
if (!mmap_lock_speculate_try_begin(mm, &seq))
return NULL;
