From: Vincent Donnefort Date: Fri, 10 Apr 2026 12:45:27 +0000 (+0100) Subject: ring-buffer: Prevent off-by-one array access in ring_buffer_desc_page() X-Git-Url: http://git.ipfire.org/index.cgi?a=commitdiff_plain;h=6170922f137231b98fc568571befef63e1edff3f;p=thirdparty%2Fkernel%2Flinux.git ring-buffer: Prevent off-by-one array access in ring_buffer_desc_page() As pointed out by Smatch, the ring-buffer descriptor array page_va is counted by nr_page_va, but the accessor ring_buffer_desc_page() allows access off by one. Currently, this does not cause problems, as the page ID always comes from a trusted source. Nonetheless, ensure robustness and fix the accessor. While at it, make the page_id unsigned. Link: https://patch.msgid.link/20260410124527.3563970-1-vdonnefort@google.com Reported-by: Dan Carpenter Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt (Google) --- diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 839a6424d0edc..cef49f8871d2e 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -2238,9 +2238,9 @@ static struct ring_buffer_desc *ring_buffer_desc(struct trace_buffer_desc *trace return NULL; } -static void *ring_buffer_desc_page(struct ring_buffer_desc *desc, int page_id) +static void *ring_buffer_desc_page(struct ring_buffer_desc *desc, unsigned int page_id) { - return page_id > desc->nr_page_va ? NULL : (void *)desc->page_va[page_id]; + return page_id >= desc->nr_page_va ? NULL : (void *)desc->page_va[page_id]; } static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,