Commit 23b3b6f0 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

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: default avatarMing Lei <tom.leiming@gmail.com>
Link: https://patch.msgid.link/20260409133020.3780098-2-tom.leiming@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent d0cc5f58

drivers/block/ublk_drv.c

+8 −1
Original line number Diff line number Diff line
@@ -63,6 +63,9 @@ 
#define UBLK_CMD_REG_BUF	_IOC_NR(UBLK_U_CMD_REG_BUF)

#define UBLK_CMD_UNREG_BUF	_IOC_NR(UBLK_U_CMD_UNREG_BUF)



/* Default max shmem buffer size: 4GB (may be increased in future) */

#define UBLK_SHMEM_BUF_SIZE_MAX	(1ULL << 32)



#define UBLK_IO_REGISTER_IO_BUF		_IOC_NR(UBLK_U_IO_REGISTER_IO_BUF)

#define UBLK_IO_UNREGISTER_IO_BUF	_IOC_NR(UBLK_U_IO_UNREGISTER_IO_BUF)
@@ -5351,11 +5354,15 @@ static int ublk_ctrl_reg_buf(struct ublk_device *ub, 
	if (buf_reg.flags & ~UBLK_SHMEM_BUF_READ_ONLY)

		return -EINVAL;



	if (buf_reg.reserved)

		return -EINVAL;



	addr = buf_reg.addr;

	size = buf_reg.len;

	nr_pages = size >> PAGE_SHIFT;



	if (!size || !PAGE_ALIGNED(size) || !PAGE_ALIGNED(addr))

	if (!size || size > UBLK_SHMEM_BUF_SIZE_MAX ||

	    !PAGE_ALIGNED(size) || !PAGE_ALIGNED(addr))

		return -EINVAL;



	disk = ublk_get_disk(ub);

include/uapi/linux/ublk_cmd.h

+2 −1
Original line number Diff line number Diff line
@@ -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 */