From 23b3b6f0b584b70a427d5bb826d320151890d7da Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Thu, 9 Apr 2026 21:30:13 +0800 Subject: ublk: widen ublk_shmem_buf_reg.len to __u64 for 4GB buffer support The __u32 len field cannot represent a 4GB buffer (0x100000000 overflows to 0). Change it to __u64 so buffers up to 4GB can be registered. Add a reserved field for alignment and validate it is zero. The kernel enforces a default max of 4GB (UBLK_SHMEM_BUF_SIZE_MAX) which may be increased in future. Signed-off-by: Ming Lei Link: https://patch.msgid.link/20260409133020.3780098-2-tom.leiming@gmail.com Signed-off-by: Jens Axboe --- include/uapi/linux/ublk_cmd.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h index a7078b798791..6991370a72ce 100644 --- a/include/uapi/linux/ublk_cmd.h +++ b/include/uapi/linux/ublk_cmd.h @@ -89,8 +89,9 @@ /* Parameter buffer for UBLK_U_CMD_REG_BUF, pointed to by ctrl_cmd.addr */ struct ublk_shmem_buf_reg { __u64 addr; /* userspace virtual address of shared memory */ - __u32 len; /* buffer size in bytes (page-aligned, max 4GB) */ + __u64 len; /* buffer size in bytes, page-aligned, default max 4GB */ __u32 flags; + __u32 reserved; }; /* Pin pages without FOLL_WRITE; usable with write-sealed memfd */ -- cgit v1.2.3