Commit 6170922f authored by Vincent Donnefort's avatar Vincent Donnefort Committed by Steven Rostedt (Google)
Browse files

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: default avatarDan Carpenter <error27@gmail.com>
Signed-off-by: default avatarVincent Donnefort <vdonnefort@google.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 1111e9bd

kernel/trace/ring_buffer.c

+2 −2
Original line number Diff line number Diff line
@@ -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,