[PATCH] dm: restrict dm device size to 2^63-512 bytes

[Mikulas Patocka]

The devices with size >= 2^63 bytes can't be used reliably by userspace
because the type off_t is a signed 64-bit integer.

Therefore, we limit the maximum size of a device mapper device to
2^63-512 bytes.

Signed-off-by: Mikulas Patocka <mpato...@redhat.com>

---
 drivers/md/dm-table.c |    4 ++++
 1 file changed, 4 insertions(+)

Index: linux-2.6/drivers/md/dm-table.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-table.c        2025-02-24 12:41:49.000000000 
+0100
+++ linux-2.6/drivers/md/dm-table.c     2025-03-14 13:42:13.000000000 +0100
@@ -697,6 +697,10 @@ int dm_table_add_target(struct dm_table
                DMERR("%s: zero-length target", dm_device_name(t->md));
                return -EINVAL;
        }
+       if (start + len < start || start + len > LLONG_MAX >> SECTOR_SHIFT) {
+               DMERR("%s: too large device", dm_device_name(t->md));
+               return -EINVAL;
+       }
 
        ti->type = dm_get_target_type(type);
        if (!ti->type) {