[PATCH 5.10 124/491] lib/bootconfig: fix off-by-one in xbc_verify_tree() unclosed brace error

Greg Kroah-Hartman
2026-04-13T16:47:59Z

From: Josh Law <objecting@objecting.org>

commit 39ebc8d7f561e1b64eca87353ef9b18e2825e591 upstream.

__xbc_open_brace() pushes entries with post-increment
(open_brace[brace_index++]), so brace_index always points one past
the last valid entry. xbc_verify_tree() reads open_brace[brace_index]
to report which brace is unclosed, but this is one past the last
pushed entry and contains stale/zero data, causing the error message
to reference the wrong node.

Use open_brace[brace_index - 1] to correctly identify the unclosed
brace. brace_index is known to be > 0 here since we are inside the
if (brace_index) guard.

Link: https://lore.kernel.org/all/20260312191143.28719-2-objecting@objecting.org/

Fixes: ead1e19ad905 ("lib/bootconfig: Fix a bug of breaking existing tree nodes")
Cc: stable@vger.kernel.org
Signed-off-by: Josh Law <objecting@objecting.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
lib/bootconfig.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/lib/bootconfig.c
+++ b/lib/bootconfig.c
@@ -685,7 +685,7 @@ static int __init xbc_verify_tree(void)

/* Brace closing */
if (brace_index) {
- n = &xbc_nodes[open_brace[brace_index]];
+ n = &xbc_nodes[open_brace[brace_index - 1]];
return xbc_parse_error("Brace is not closed",
xbc_node_get_data(n));
}