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bootconfig: skip internal tree sanity checks in kernel

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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/178913600409.248794.12941798680046327623.stgit@devnote2
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Sang-Heon Jeon <ekffu200098@gmail.com>
Closes: https://lore.kernel.org/all/20260905141637.1547429-1-ekffu200098@gmail.com/
Reviewed-by: Sang-Heon Jeon <ekffu200098@gmail.com>
This commit is contained in:
Masami Hiramatsu (Google) 2026-09-11 23:13:24 +09:00 committed by Andrew Morton
parent d6f97fcebd
commit 5c45831072
1 changed files with 26 additions and 12 deletions
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38
lib/bootconfig.c
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@ -1002,9 +1002,30 @@ static int __init xbc_close_brace(char **k, char *n)
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;
@ -1021,17 +1042,6 @@ 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;
@ -1202,6 +1212,10 @@ int __init xbc_init(const char *data, size_t size, const char **emsg, int *epos)
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)