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ublk: widen ublk_shmem_buf_reg.len to __u64 for 4GB buffer support

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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 <tom.leiming@gmail.com>
Link: https://patch.msgid.link/20260409133020.3780098-2-tom.leiming@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2026-04-09 21:30:13 +08:00 committed by Jens Axboe
parent d0cc5f585f
commit 23b3b6f0b5
2 changed files with 10 additions and 2 deletions
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9
drivers/block/ublk_drv.c
View File

@ -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);

3
include/uapi/linux/ublk_cmd.h
View File

@ -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 */