[PATCH] ring-buffer: Fix subbuf_ids memory leak in rb_allocate_cpu_buffer() error path

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

In rb_allocate_cpu_buffer(), cpu_buffer->subbuf_ids is allocated using
kcalloc() when buffer->remote is non-NULL. If a subsequent page allocation
fails (e.g., ring_buffer_desc_page() returns NULL or rb_allocate_pages()
fails), execution jumps to fail_free_reader.

While __free(kfree) automatically frees the outer cpu_buffer structure
at scope exit, kfree(cpu_buffer) does not recursively free nested heap
pointers such as cpu_buffer->subbuf_ids, resulting in a memory leak.

Fix this by explicitly freeing cpu_buffer->subbuf_ids in the
fail_free_reader error unwinding path when cpu_buffer->remote is set.

Fixes: 2e67fabd8b77 ("ring-buffer: Introduce ring-buffer remotes")
Assisted-by: Antigravity:gemini-3.6-flash
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 kernel/trace/ring_buffer.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 78d3875a47a5..03f6baf6a5f5 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c

@@ -2599,6 +2599,8 @@ rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
 	return_ptr(cpu_buffer);
 
  fail_free_reader:
+	if (cpu_buffer->remote)
+		kfree(cpu_buffer->subbuf_ids);
 	free_buffer_page(cpu_buffer->reader_page);
 
 	return NULL;