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Thu, 09 Apr 2026 06:30:38 -0700 (PDT) From: Ming Lei To: Jens Axboe , linux-block@vger.kernel.org Cc: Caleb Sander Mateos , Ming Lei Subject: [PATCH 1/7] ublk: widen ublk_shmem_buf_reg.len to __u64 for 4GB buffer support Date: Thu, 9 Apr 2026 21:30:13 +0800 Message-ID: <20260409133020.3780098-2-tom.leiming@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260409133020.3780098-1-tom.leiming@gmail.com> References: <20260409133020.3780098-1-tom.leiming@gmail.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- drivers/block/ublk_drv.c | 9 ++++++++- include/uapi/linux/ublk_cmd.h | 3 ++- 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index 2e475bdc54dd..ada9a2e32ea9 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -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); diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h index ecd258847d3d..66d93efccd51 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 */ -- 2.53.0