[PATCH v2 3/5] liveupdate: validate restored LUO session metadata

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

The restored FDT contains the physical address of the LUO session header,
which LUO maps before reading session metadata. Check that physical range
against KHO-preserved memory before calling phys_to_virt(), and abort the
restore if the physical range is not covered.

The session header has a count that controls how far LUO walks the
serialized session array. Check that count against LUO_SESSION_MAX before
deserialization, and abort the restore if the value is out of range.

Signed-off-by: Cris Jacob Maamor <crisjacobmaamor@gmail.com>
---
 kernel/liveupdate/luo_session.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
index a3327a28fc1f..0244c071936d 100644
--- a/kernel/liveupdate/luo_session.c
+++ b/kernel/liveupdate/luo_session.c
@@ -501,7 +501,18 @@ int __init luo_session_setup_incoming(void *fdt_in)
 	}
 
 	header_ser_pa = get_unaligned((u64 *)ptr);
+	if (!kho_is_preserved(header_ser_pa, LUO_SESSION_PGCNT)) {
+		pr_err("Session header is not KHO preserved: %#llx\n",
+		       (unsigned long long)header_ser_pa);
+		return -EINVAL;
+	}
+
 	header_ser = phys_to_virt(header_ser_pa);
+	if (header_ser->count > LUO_SESSION_MAX) {
+		pr_err("Invalid session count: %llu\n",
+		       (unsigned long long)header_ser->count);
+		return -EINVAL;
+	}
 
 	luo_session_global.incoming.header_ser = header_ser;
 	luo_session_global.incoming.ser = (void *)(header_ser + 1);
@@ -515,6 +526,7 @@ int luo_session_deserialize(void)
 	struct luo_session_header *sh = &luo_session_global.incoming;
 	static bool is_deserialized;
 	static int err;
+	u64 count;
 
 	/* If has been deserialized, always return the same error code */
 	if (is_deserialized)
@@ -524,6 +536,13 @@ int luo_session_deserialize(void)
 	if (!sh->active)
 		return 0;
 
+	count = sh->header_ser->count;
+	if (count > LUO_SESSION_MAX) {
+		pr_err("Invalid session count: %llu\n",
+		       (unsigned long long)count);
+		return -EINVAL;
+	}
+
 	/*
 	 * Note on error handling:
 	 *
@@ -539,7 +558,7 @@ int luo_session_deserialize(void)
 	 * userspace to detect the failure and trigger a reboot, which will
 	 * reliably reset devices and reclaim memory.
 	 */
-	for (int i = 0; i < sh->header_ser->count; i++) {
+	for (u64 i = 0; i < count; i++) {
 		struct luo_session *session;
 
 		session = luo_session_alloc(sh->ser[i].name);
@@ -606,4 +625,3 @@ int luo_session_serialize(void)
 
 	return err;
 }
-
-- 
2.53.0