+ bootconfig-skip-internal-tree-sanity-checks-in-kernel.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: bootconfig: skip internal tree sanity checks in kernel
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     bootconfig-skip-internal-tree-sanity-checks-in-kernel.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/bootconfig-skip-internal-tree-sanity-checks-in-kernel.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Subject: bootconfig: skip internal tree sanity checks in kernel
Date: Thu, 10 Sep 2026 00:54:02 +0900

In xbc_verify_tree(), the loop iterating through all nodes to check that
xbc_nodes[i].next < xbc_node_num and xbc_nodes[i].child < xbc_node_num is
a defensive sanity check against implementation regressions (such an
out-of-bounds index cannot be produced by malformed input).

Running this check in the kernel adds unnecessary boot-time overhead. 
Split this check out into xbc_sanity_check_tree() for userspace, so that
it continues to run during userspace bootconfig validation (e.g.  when
applying or testing bootconfig with tools/bootconfig), but is omitted in
the kernel to speed up initialization.

Link: https://lore.kernel.org/178896924262.177508.71609739247457811.stgit@devnote2
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reported-by: Sang-Heon Jeon <ekffu200098@gmail.com>
Closes: https://lore.kernel.org/all/20260905141637.1547429-1-ekffu200098@gmail.com/
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 lib/bootconfig.c |   38 ++++++++++++++++++++++++++------------
 1 file changed, 26 insertions(+), 12 deletions(-)

--- a/lib/bootconfig.c~bootconfig-skip-internal-tree-sanity-checks-in-kernel
+++ a/lib/bootconfig.c
@@ -1003,9 +1003,30 @@ static int __init xbc_close_brace(char *
 	return __xbc_close_brace(n - 1);
 }
 
+#ifndef __KERNEL__
+/* Sanity check for regression: node indices must be within bounds */
+static int __init xbc_sanity_check_tree(void)
+{
+	int i;
+
+	for (i = 0; i < xbc_node_num; i++) {
+		if (xbc_nodes[i].next >= xbc_node_num) {
+			return xbc_parse_error("No closing brace",
+				xbc_node_get_data(xbc_nodes + i));
+		}
+		if (xbc_nodes[i].child >= xbc_node_num) {
+			return xbc_parse_error("Broken child node",
+				xbc_node_get_data(xbc_nodes + i));
+		}
+	}
+
+	return 0;
+}
+#endif
+
 static int __init xbc_verify_tree(void)
 {
-	int i, depth;
+	int depth;
 	size_t len, wlen;
 	struct xbc_node *n, *m;
 
@@ -1022,17 +1043,6 @@ static int __init xbc_verify_tree(void)
 		return -ENOENT;
 	}
 
-	for (i = 0; i < xbc_node_num; i++) {
-		if (xbc_nodes[i].next >= xbc_node_num) {
-			return xbc_parse_error("No closing brace",
-				xbc_node_get_data(xbc_nodes + i));
-		}
-		if (xbc_nodes[i].child >= xbc_node_num) {
-			return xbc_parse_error("Broken child node",
-				xbc_node_get_data(xbc_nodes + i));
-		}
-	}
-
 	/* Key tree limitation check */
 	n = &xbc_nodes[0];
 	depth = 1;
@@ -1203,6 +1213,10 @@ int __init xbc_init(const char *data, si
 	ret = xbc_parse_tree();
 	if (!ret)
 		ret = xbc_verify_tree();
+#ifndef __KERNEL__
+	if (!ret)
+		ret = xbc_sanity_check_tree();
+#endif
 
 	if (ret < 0) {
 		if (epos)
_

Patches currently in -mm which might be from mhiramat@kernel.org are

bootconfig-reject-unexpected-data-after-null-character.patch
tools-bootconfig-consolidate-xbc_init-to-error-message-wrapper.patch
bootconfig-skip-internal-tree-sanity-checks-in-kernel.patch