Commit d471d4f86e86 for kernel

commit d471d4f86e8689ad15309e49da8e5e4e9bb9ce87
Author: Vincent Donnefort <vdonnefort@google.com>
Date:   Thu Jul 9 17:00:16 2026 +0100

    tracing/remotes: Fix struct_len in trace_remote_alloc_buffer()

    Pre-calculate desc->struct_len up-front in trace_remote_alloc_buffer()
    with trace_buffer_desc_size() to fix double-counting.

    While at it, use the accessor __first_ring_buffer_desc().

    Link: https://patch.msgid.link/20260709160017.1729517-3-vdonnefort@google.com
    Fixes: 96e43537af54 ("tracing: Introduce trace remotes")
    Reported-by: Sashiko <sashiko-bot@kernel.org>
    Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_remote.c b/kernel/trace/trace_remote.c
index d48042239d58..0f6ef5c36d84 100644
--- a/kernel/trace/trace_remote.c
+++ b/kernel/trace/trace_remote.c
@@ -979,27 +979,22 @@ EXPORT_SYMBOL_GPL(trace_remote_free_buffer);
 int trace_remote_alloc_buffer(struct trace_buffer_desc *desc, size_t desc_size, size_t buffer_size,
 			      const struct cpumask *cpumask)
 {
+	size_t min_desc_size = trace_buffer_desc_size(buffer_size, cpumask_weight(cpumask));
 	unsigned int nr_pages = max(DIV_ROUND_UP(buffer_size, PAGE_SIZE), 2UL) + 1;
-	void *desc_end = desc + desc_size;
 	struct ring_buffer_desc *rb_desc;
 	int cpu, ret = -ENOMEM;

-	if (desc_size < struct_size(desc, __data, 0))
+	if (desc_size < min_desc_size)
 		return -EINVAL;

 	desc->nr_cpus = 0;
-	desc->struct_len = struct_size(desc, __data, 0);
+	desc->struct_len = min_desc_size;

-	rb_desc = (struct ring_buffer_desc *)&desc->__data[0];
+	rb_desc = __first_ring_buffer_desc(desc);

 	for_each_cpu(cpu, cpumask) {
 		unsigned int id;

-		if ((void *)rb_desc + struct_size(rb_desc, page_va, nr_pages) > desc_end) {
-			ret = -EINVAL;
-			goto err;
-		}
-
 		rb_desc->cpu = cpu;
 		rb_desc->nr_page_va = 0;
 		rb_desc->meta_va = (unsigned long)__get_free_page(GFP_KERNEL);
@@ -1015,8 +1010,6 @@ int trace_remote_alloc_buffer(struct trace_buffer_desc *desc, size_t desc_size,

 			rb_desc->nr_page_va++;
 		}
-		desc->struct_len += offsetof(struct ring_buffer_desc, page_va);
-		desc->struct_len += struct_size(rb_desc, page_va, rb_desc->nr_page_va);
 		rb_desc = __next_ring_buffer_desc(rb_desc);
 	}