[PATCH v2 2/5] liveupdate: validate LUO FDT physical address before mapping

[Cris Jacob Maamor <crisjacobmaamor@gmail.com>]

LUO gets the restored FDT address from KHO and maps it with phys_to_virt().

Check the FDT size and make sure the address range is KHO-preserved before
mapping it. Reject empty or oversized FDT metadata.

Signed-off-by: Cris Jacob Maamor <crisjacobmaamor@gmail.com>
---
 kernel/liveupdate/luo_core.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c
index 803f51c84275..633a16434164 100644
--- a/kernel/liveupdate/luo_core.c
+++ b/kernel/liveupdate/luo_core.c
@@ -82,6 +82,7 @@ early_param("liveupdate", early_liveupdate_param);
 
 static int __init luo_early_startup(void)
 {
+	size_t fdt_size;
 	phys_addr_t fdt_phys;
 	int err, ln_size;
 	const void *ptr;
@@ -94,7 +95,8 @@ static int __init luo_early_startup(void)
 	}
 
 	/* Retrieve LUO subtree, and verify its format. */
-	err = kho_retrieve_subtree(LUO_FDT_KHO_ENTRY_NAME, &fdt_phys, NULL);
+	err = kho_retrieve_subtree(LUO_FDT_KHO_ENTRY_NAME, &fdt_phys,
+				   &fdt_size);
 	if (err) {
 		if (err != -ENOENT) {
 			pr_err("failed to retrieve FDT '%s' from KHO: %pe\n",
@@ -105,6 +107,12 @@ static int __init luo_early_startup(void)
 		return 0;
 	}
 
+	if (!fdt_size || fdt_size > LUO_FDT_SIZE ||
+	    !kho_is_preserved(fdt_phys, DIV_ROUND_UP(fdt_size, PAGE_SIZE))) {
+		pr_err("Invalid LUO FDT from KHO\n");
+		return -EINVAL;
+	}
+
 	luo_global.fdt_in = phys_to_virt(fdt_phys);
 	err = fdt_node_check_compatible(luo_global.fdt_in, 0,
 					LUO_FDT_COMPATIBLE);
-- 
2.53.0