From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Josh Law <objecting@objecting.org>,
	"Masami Hiramatsu (Google)" <mhiramat@kernel.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.12 457/460] lib/bootconfig: check xbc_init_node() return in override path
Date: Mon, 23 Mar 2026 14:47:33 +0100
Message-ID: <20260323134537.805805516@linuxfoundation.org>
In-Reply-To: <20260323134526.647552166@linuxfoundation.org>
References: <20260323134526.647552166@linuxfoundation.org>
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6.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Josh Law <objecting@objecting.org>

[ Upstream commit bb288d7d869e86d382f35a0e26242c5ccb05ca82 ]

The ':=' override path in xbc_parse_kv() calls xbc_init_node() to
re-initialize an existing value node but does not check the return
value. If xbc_init_node() fails (data offset out of range), parsing
silently continues with stale node data.

Add the missing error check to match the xbc_add_node() call path
which already checks for failure.

In practice, a bootconfig using ':=' to override a value near the
32KB data limit could silently retain the old value, meaning a
security-relevant boot parameter override (e.g., a trace filter or
debug setting) would not take effect as intended.

Link: https://lore.kernel.org/all/20260318155847.78065-2-objecting@objecting.org/

Fixes: e5efaeb8a8f5 ("bootconfig: Support mixing a value and subkeys under a key")
Signed-off-by: Josh Law <objecting@objecting.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 lib/bootconfig.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/bootconfig.c b/lib/bootconfig.c
index 0728c4a95249b..5d3802eba52a3 100644
--- a/lib/bootconfig.c
+++ b/lib/bootconfig.c
@@ -712,7 +712,8 @@ static int __init xbc_parse_kv(char **k, char *v, int op)
 		if (op == ':') {
 			unsigned short nidx = child->next;
 
-			xbc_init_node(child, v, XBC_VALUE);
+			if (xbc_init_node(child, v, XBC_VALUE) < 0)
+				return xbc_parse_error("Failed to override value", v);
 			child->next = nidx;	/* keep subkeys */
 			goto array;
 		}
-- 
2.51.0