lib/bootconfig: increment xbc_node_num after node init succeeds

Move the xbc_node_num increment to after xbc_init_node() so a failed
init does not leave a partially initialized node counted in the array.

If xbc_init_node() fails on a data offset at the boundary of a
maximum-size bootconfig, the pre-incremented count causes subsequent
tree verification and traversal to consider the uninitialized node as
valid, potentially leading to an out-of-bounds read or unpredictable
boot behavior.

Link: https://lore.kernel.org/all/20260318155919.78168-5-objecting@objecting.org/
Signed-off-by: Josh Law <objecting@objecting.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

diff --git a/lib/bootconfig.c b/lib/bootconfig.c
index 8858862122487cf14a0edafa1922f5a6d46cdce5..c02b11a1b50192d359ea1f45d5034d5ac52ce108 100644 (file)
--- a/lib/bootconfig.c
+++ b/lib/bootconfig.c
@@ -429,9 +429,10 @@ static struct xbc_node * __init xbc_add_node(char *data, uint16_t flag)
        if (xbc_node_num == XBC_NODE_MAX)
                return NULL;
 
-       node = &xbc_nodes[xbc_node_num++];
+       node = &xbc_nodes[xbc_node_num];
        if (xbc_init_node(node, data, flag) < 0)
                return NULL;
+       xbc_node_num++;
 
        return node;
 }