The following commit has been merged into the perf/core branch of tip:
Commit-ID: 4621928fabc474d0ccab9e91f13b6f9f344e8248
Gitweb: https://git.kernel.org/tip/4621928fabc474d0ccab9e91f13b6f9f344e8248
Author: Andrii Nakryiko <andrii@xxxxxxxxxx>
AuthorDate: Thu, 05 Dec 2024 16:24:16 -08:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 09 Dec 2024 11:18:08 +01:00
uprobes: Ensure return_instance is detached from the list before freeing
Ensure that by the time we call free_ret_instance() to clean up an
instance of struct return_instance it isn't reachable from
utask->return_instances anymore.
free_ret_instance() is called in a few different situations, all but one
of which already are fine w.r.t. return_instance visibility:
- uprobe_free_utask() guarantees that ri_timer() won't be called
(through timer_delete_sync() call), and so there is no need to
unlink anything, because entire utask is being freed;
- uprobe_handle_trampoline() is already unlinking to-be-freed
return_instance with rcu_assign_pointer() before calling
free_ret_instance().
Only cleanup_return_instances() violates this property, which so far is
not causing problems due to RCU-delayed freeing of return_instance,
which we'll change in the next patch. So make sure we unlink
return_instance before passing it into free_ret_instance(), as otherwise
reuse will be unsafe.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20241206002417.3295533-4-andrii@xxxxxxxxxx
---
kernel/events/uprobes.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index cca1fe4..2345aeb 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -2116,12 +2116,12 @@ static void cleanup_return_instances(struct uprobe_task *utask, bool chained,
while (ri && !arch_uretprobe_is_alive(ri, ctx, regs)) {
ri_next = ri->next;
+ rcu_assign_pointer(utask->return_instances, ri_next);
utask->depth--;
free_ret_instance(ri, true /* cleanup_hprobe */);
ri = ri_next;
}
- rcu_assign_pointer(utask->return_instances, ri);
}
static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs,
|