* [PATCH v2 2/2] luo: Update serialized data to KHOSER_PTR
2026-06-16 13:23 [PATCH v2 0/2] luo: migrate serialized_data to type-safe KHO pointers Tarun Sahu
2026-06-16 13:23 ` [PATCH v2 1/2] kho: add KHOSER_COPY_TYPE(UN)SAFE for phys copy Tarun Sahu
@ 2026-06-16 13:23 ` Tarun Sahu
1 sibling, 0 replies; 3+ messages in thread
From: Tarun Sahu @ 2026-06-16 13:23 UTC (permalink / raw)
To: Alexander Graf, Pratyush Yadav, Mike Rapoport, Andrew Morton,
Pasha Tatashin
Cc: linux-kernel, linux-mm, kexec, Tarun Sahu
Currently luo_file_ser, luo_file and liveupdate_file_op_args use the raw
serialized_data which stores the phys address of the serialized data. There
are two issues
1. It uses raw update, and there is not type safety check
2. user of liveupdate_file_op_args, uses virt_to_phys and phys_to_virt
to convert the serializeable pointer to physical address and vice versa.
User makes mistakes mistake to check the serializeable pointer/phys
value check before converting like in memfd_luo.
Converting them to serializeable pointer enforce type safety check ( it has
its limitation as you can not have generic serializeable pointer for all
the subsystem. So only void * is the only choice, and updating it require
user to use KHOSER_COPY_TYPEUNSAFE) and the null value check.
This patch also updates the memfd_luo to use the newly introduced the
serializeable pointer. Which mitigates the issue of not checking
args->serialized_data pointer before using it.
Fixes: b3749f174d68 ("mm: memfd_luo: allow preserving memfd")
Signed-off-by: Tarun Sahu <tarunsahu@google.com>
---
include/linux/kho/abi/luo.h | 6 ++++--
include/linux/liveupdate.h | 4 ++--
kernel/liveupdate/luo_file.c | 24 ++++++++++++------------
mm/memfd_luo.c | 18 +++++++++---------
4 files changed, 27 insertions(+), 25 deletions(-)
diff --git a/include/linux/kho/abi/luo.h b/include/linux/kho/abi/luo.h
index 46750a0ddf88..6b08fbf7ad59 100644
--- a/include/linux/kho/abi/luo.h
+++ b/include/linux/kho/abi/luo.h
@@ -119,17 +119,19 @@
#define LIVEUPDATE_HNDL_COMPAT_LENGTH 48
+#include <linux/kho/abi/kexec_handover.h>
+
/**
* struct luo_file_ser - Represents the serialized preserves files.
* @compatible: File handler compatible string.
- * @data: Private data
+ * @serialized_data: Serializable pointer union for private data.
* @token: User provided token for this file
*
* If this structure is modified, LUO_SESSION_COMPATIBLE must be updated.
*/
struct luo_file_ser {
char compatible[LIVEUPDATE_HNDL_COMPAT_LENGTH];
- u64 data;
+ DECLARE_KHOSER_PTR(serialized_data, void *);
u64 token;
} __packed;
diff --git a/include/linux/liveupdate.h b/include/linux/liveupdate.h
index 30c5a39ff9e9..8b3466801159 100644
--- a/include/linux/liveupdate.h
+++ b/include/linux/liveupdate.h
@@ -32,7 +32,7 @@ struct file;
* @file: The file object. For retrieve: [OUT] The callback sets
* this to the new file. For other ops: [IN] The caller sets
* this to the file being operated on.
- * @serialized_data: The opaque u64 handle, preserve/prepare/freeze may update
+ * @serialized_data: The serialized pointer union, preserve/prepare/freeze may update
* this field.
* @private_data: Private data for the file used to hold runtime state that
* is not preserved. Set by the handler's .preserve()
@@ -46,7 +46,7 @@ struct liveupdate_file_op_args {
struct liveupdate_file_handler *handler;
int retrieve_status;
struct file *file;
- u64 serialized_data;
+ DECLARE_KHOSER_PTR(serialized_data, void *);
void *private_data;
};
diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
index a0a419085e28..c50c8239a34d 100644
--- a/kernel/liveupdate/luo_file.c
+++ b/kernel/liveupdate/luo_file.c
@@ -130,7 +130,7 @@ static DEFINE_XARRAY(luo_preserved_files);
* @file: Pointer to the kernel's &struct file that is being preserved.
* This is NULL in the new kernel until the file is successfully
* retrieved.
- * @serialized_data: The opaque u64 handle to the serialized state of the file.
+ * @serialized_data: The serialized pointer union to the serialized state of the file.
* This handle is passed back to the handler's .freeze(),
* .retrieve(), and .finish() callbacks, allowing it to track
* and update its serialized state across phases.
@@ -166,7 +166,7 @@ static DEFINE_XARRAY(luo_preserved_files);
struct luo_file {
struct liveupdate_file_handler *fh;
struct file *file;
- u64 serialized_data;
+ DECLARE_KHOSER_PTR(serialized_data, void *);
void *private_data;
int retrieve_status;
struct mutex mutex;
@@ -328,7 +328,7 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)
if (err)
goto err_kfree;
- luo_file->serialized_data = args.serialized_data;
+ KHOSER_COPY_TYPESAFE(luo_file->serialized_data, args.serialized_data);
luo_file->private_data = args.private_data;
list_add_tail(&luo_file->list, &file_set->files_list);
file_set->count++;
@@ -381,7 +381,7 @@ void luo_file_unpreserve_files(struct luo_file_set *file_set)
args.handler = luo_file->fh;
args.file = luo_file->file;
- args.serialized_data = luo_file->serialized_data;
+ KHOSER_COPY_TYPESAFE(args.serialized_data, luo_file->serialized_data);
args.private_data = luo_file->private_data;
luo_file->fh->ops->unpreserve(&args);
luo_flb_file_unpreserve(luo_file->fh);
@@ -412,12 +412,12 @@ static int luo_file_freeze_one(struct luo_file_set *file_set,
args.handler = luo_file->fh;
args.file = luo_file->file;
- args.serialized_data = luo_file->serialized_data;
+ KHOSER_COPY_TYPESAFE(args.serialized_data, luo_file->serialized_data);
args.private_data = luo_file->private_data;
err = luo_file->fh->ops->freeze(&args);
if (!err)
- luo_file->serialized_data = args.serialized_data;
+ KHOSER_COPY_TYPESAFE(luo_file->serialized_data, args.serialized_data);
}
return err;
@@ -433,7 +433,7 @@ static void luo_file_unfreeze_one(struct luo_file_set *file_set,
args.handler = luo_file->fh;
args.file = luo_file->file;
- args.serialized_data = luo_file->serialized_data;
+ KHOSER_COPY_TYPESAFE(args.serialized_data, luo_file->serialized_data);
args.private_data = luo_file->private_data;
luo_file->fh->ops->unfreeze(&args);
@@ -515,7 +515,7 @@ int luo_file_freeze(struct luo_file_set *file_set,
strscpy(file_ser[i].compatible, luo_file->fh->compatible,
sizeof(file_ser[i].compatible));
- file_ser[i].data = luo_file->serialized_data;
+ KHOSER_COPY_TYPESAFE(file_ser[i].serialized_data, luo_file->serialized_data);
file_ser[i].token = luo_file->token;
i++;
}
@@ -621,7 +621,7 @@ int luo_retrieve_file(struct luo_file_set *file_set, u64 token,
}
args.handler = luo_file->fh;
- args.serialized_data = luo_file->serialized_data;
+ KHOSER_COPY_TYPESAFE(args.serialized_data, luo_file->serialized_data);
err = luo_file->fh->ops->retrieve(&args);
if (err) {
/* Keep the error code for later use. */
@@ -655,7 +655,7 @@ static int luo_file_can_finish_one(struct luo_file_set *file_set,
args.handler = luo_file->fh;
args.file = luo_file->file;
- args.serialized_data = luo_file->serialized_data;
+ KHOSER_COPY_TYPESAFE(args.serialized_data, luo_file->serialized_data);
args.retrieve_status = luo_file->retrieve_status;
can_finish = luo_file->fh->ops->can_finish(&args);
}
@@ -672,7 +672,7 @@ static void luo_file_finish_one(struct luo_file_set *file_set,
args.handler = luo_file->fh;
args.file = luo_file->file;
- args.serialized_data = luo_file->serialized_data;
+ KHOSER_COPY_TYPESAFE(args.serialized_data, luo_file->serialized_data);
args.retrieve_status = luo_file->retrieve_status;
luo_file->fh->ops->finish(&args);
@@ -837,7 +837,7 @@ int luo_file_deserialize(struct luo_file_set *file_set,
luo_file->fh = fh;
luo_file->file = NULL;
- luo_file->serialized_data = file_ser[i].data;
+ KHOSER_COPY_TYPESAFE(luo_file->serialized_data, file_ser[i].serialized_data);
luo_file->token = file_ser[i].token;
mutex_init(&luo_file->mutex);
list_add_tail(&luo_file->list, &file_set->files_list);
diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c
index 59de210bee5f..daf2c4c3da35 100644
--- a/mm/memfd_luo.c
+++ b/mm/memfd_luo.c
@@ -257,6 +257,7 @@ static void memfd_luo_unpreserve_folios(struct kho_vmalloc *kho_vmalloc,
static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
{
+ DECLARE_KHOSER_PTR(sd, struct memfd_luo_ser *);
struct inode *inode = file_inode(args->file);
struct memfd_luo_folio_ser *folios_ser;
struct memfd_luo_ser *ser;
@@ -309,7 +310,8 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
inode_unlock(inode);
args->private_data = folios_ser;
- args->serialized_data = virt_to_phys(ser);
+ KHOSER_STORE_PTR(sd, ser);
+ KHOSER_COPY_TYPEUNSAFE(args->serialized_data, sd);
return 0;
@@ -325,11 +327,10 @@ static int memfd_luo_freeze(struct liveupdate_file_op_args *args)
{
struct memfd_luo_ser *ser;
- if (WARN_ON_ONCE(!args->serialized_data))
+ ser = KHOSER_LOAD_PTR(args->serialized_data);
+ if (WARN_ON_ONCE(!ser))
return -EINVAL;
- ser = phys_to_virt(args->serialized_data);
-
/*
* The pos might have changed since prepare. Everything else stays the
* same.
@@ -344,14 +345,13 @@ static void memfd_luo_unpreserve(struct liveupdate_file_op_args *args)
struct inode *inode = file_inode(args->file);
struct memfd_luo_ser *ser;
- if (WARN_ON_ONCE(!args->serialized_data))
+ ser = KHOSER_LOAD_PTR(args->serialized_data);
+ if (WARN_ON_ONCE(!ser))
return;
inode_lock(inode);
shmem_freeze(inode, false);
- ser = phys_to_virt(args->serialized_data);
-
memfd_luo_unpreserve_folios(&ser->folios, args->private_data,
ser->nr_folios);
@@ -397,7 +397,7 @@ static void memfd_luo_finish(struct liveupdate_file_op_args *args)
if (args->retrieve_status)
return;
- ser = phys_to_virt(args->serialized_data);
+ ser = KHOSER_LOAD_PTR(args->serialized_data);
if (!ser)
return;
@@ -522,7 +522,7 @@ static int memfd_luo_retrieve(struct liveupdate_file_op_args *args)
struct file *file;
int err;
- ser = phys_to_virt(args->serialized_data);
+ ser = KHOSER_LOAD_PTR(args->serialized_data);
if (!ser)
return -EINVAL;
--
2.54.0.1136.gdb2ca164c4-goog
^ permalink raw reply related [flat|nested] 3+ messages in thread