ublk: use READ_ONCE() to read struct ublksrv_ctrl_cmd

struct ublksrv_ctrl_cmd is part of the io_uring_sqe, which may lie in
userspace-mapped memory. It's racy to access its fields with normal
loads, as userspace may write to them concurrently. Use READ_ONCE() to
copy the ublksrv_ctrl_cmd from the io_uring_sqe to the stack. Use the
local copy in place of the one in the io_uring_sqe.

Fixes: 87213b0d847c ("ublk: allow non-blocking ctrl cmds in IO_URING_F_NONBLOCK issue")
Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 01088194c8d35d2ecd547c7296a3d0b385aee3ee..8122b012a7ae8d5f4076b666d104ccc21f95165a 100644 (file)
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -4731,12 +4731,11 @@ static int ublk_ctrl_del_dev(struct ublk_device **p_ub, bool wait)
        return 0;
 }
 
-static inline void ublk_ctrl_cmd_dump(struct io_uring_cmd *cmd)
+static inline void ublk_ctrl_cmd_dump(u32 cmd_op,
+                                     const struct ublksrv_ctrl_cmd *header)
 {
-       const struct ublksrv_ctrl_cmd *header = io_uring_sqe_cmd(cmd->sqe);
-
        pr_devel("%s: cmd_op %x, dev id %d qid %d data %llx buf %llx len %u\n",
-                       __func__, cmd->cmd_op, header->dev_id, header->queue_id,
+                       __func__, cmd_op, header->dev_id, header->queue_id,
                        header->data[0], header->addr, header->len);
 }
 
@@ -5119,9 +5118,8 @@ exit:
 }
 
 static int ublk_ctrl_uring_cmd_permission(struct ublk_device *ub,
-               struct io_uring_cmd *cmd)
+               u32 cmd_op, struct ublksrv_ctrl_cmd *header)
 {
-       struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)io_uring_sqe_cmd(cmd->sqe);
        bool unprivileged = ub->dev_info.flags & UBLK_F_UNPRIVILEGED_DEV;
        void __user *argp = (void __user *)(unsigned long)header->addr;
        char *dev_path = NULL;
@@ -5137,7 +5135,7 @@ static int ublk_ctrl_uring_cmd_permission(struct ublk_device *ub,
                 * know if the specified device is created as unprivileged
                 * mode.
                 */
-               if (_IOC_NR(cmd->cmd_op) != UBLK_CMD_GET_DEV_INFO2)
+               if (_IOC_NR(cmd_op) != UBLK_CMD_GET_DEV_INFO2)
                        return 0;
        }
 
@@ -5158,7 +5156,7 @@ static int ublk_ctrl_uring_cmd_permission(struct ublk_device *ub,
                return PTR_ERR(dev_path);
 
        ret = -EINVAL;
-       switch (_IOC_NR(cmd->cmd_op)) {
+       switch (_IOC_NR(cmd_op)) {
        case UBLK_CMD_GET_DEV_INFO:
        case UBLK_CMD_GET_DEV_INFO2:
        case UBLK_CMD_GET_QUEUE_AFFINITY:
@@ -5188,7 +5186,7 @@ static int ublk_ctrl_uring_cmd_permission(struct ublk_device *ub,
                header->addr += header->dev_path_len;
        }
        pr_devel("%s: dev id %d cmd_op %x uid %d gid %d path %s ret %d\n",
-                       __func__, ub->ub_number, cmd->cmd_op,
+                       __func__, ub->ub_number, cmd_op,
                        ub->dev_info.owner_uid, ub->dev_info.owner_gid,
                        dev_path, ret);
 exit:
@@ -5212,7 +5210,9 @@ static bool ublk_ctrl_uring_cmd_may_sleep(u32 cmd_op)
 static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,
                unsigned int issue_flags)
 {
-       const struct ublksrv_ctrl_cmd *header = io_uring_sqe_cmd(cmd->sqe);
+       /* May point to userspace-mapped memory */
+       const struct ublksrv_ctrl_cmd *ub_src = io_uring_sqe_cmd(cmd->sqe);
+       struct ublksrv_ctrl_cmd header;
        struct ublk_device *ub = NULL;
        u32 cmd_op = cmd->cmd_op;
        int ret = -EINVAL;
@@ -5224,31 +5224,37 @@ static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,
        if (!(issue_flags & IO_URING_F_SQE128))
                return -EINVAL;
 
-       ublk_ctrl_cmd_dump(cmd);
+       header.dev_id = READ_ONCE(ub_src->dev_id);
+       header.queue_id = READ_ONCE(ub_src->queue_id);
+       header.len = READ_ONCE(ub_src->len);
+       header.addr = READ_ONCE(ub_src->addr);
+       header.data[0] = READ_ONCE(ub_src->data[0]);
+       header.dev_path_len = READ_ONCE(ub_src->dev_path_len);
+       ublk_ctrl_cmd_dump(cmd_op, &header);
 
        ret = ublk_check_cmd_op(cmd_op);
        if (ret)
                goto out;
 
        if (cmd_op == UBLK_U_CMD_GET_FEATURES) {
-               ret = ublk_ctrl_get_features(header);
+               ret = ublk_ctrl_get_features(&header);
                goto out;
        }
 
        if (_IOC_NR(cmd_op) != UBLK_CMD_ADD_DEV) {
                ret = -ENODEV;
-               ub = ublk_get_device_from_id(header->dev_id);
+               ub = ublk_get_device_from_id(header.dev_id);
                if (!ub)
                        goto out;
 
-               ret = ublk_ctrl_uring_cmd_permission(ub, cmd);
+               ret = ublk_ctrl_uring_cmd_permission(ub, cmd_op, &header);
                if (ret)
                        goto put_dev;
        }
 
        switch (_IOC_NR(cmd_op)) {
        case UBLK_CMD_START_DEV:
-               ret = ublk_ctrl_start_dev(ub, header);
+               ret = ublk_ctrl_start_dev(ub, &header);
                break;
        case UBLK_CMD_STOP_DEV:
                ublk_ctrl_stop_dev(ub);
@@ -5256,10 +5262,10 @@ static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,
                break;
        case UBLK_CMD_GET_DEV_INFO:
        case UBLK_CMD_GET_DEV_INFO2:
-               ret = ublk_ctrl_get_dev_info(ub, header);
+               ret = ublk_ctrl_get_dev_info(ub, &header);
                break;
        case UBLK_CMD_ADD_DEV:
-               ret = ublk_ctrl_add_dev(header);
+               ret = ublk_ctrl_add_dev(&header);
                break;
        case UBLK_CMD_DEL_DEV:
                ret = ublk_ctrl_del_dev(&ub, true);
@@ -5268,26 +5274,26 @@ static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,
                ret = ublk_ctrl_del_dev(&ub, false);
                break;
        case UBLK_CMD_GET_QUEUE_AFFINITY:
-               ret = ublk_ctrl_get_queue_affinity(ub, header);
+               ret = ublk_ctrl_get_queue_affinity(ub, &header);
                break;
        case UBLK_CMD_GET_PARAMS:
-               ret = ublk_ctrl_get_params(ub, header);
+               ret = ublk_ctrl_get_params(ub, &header);
                break;
        case UBLK_CMD_SET_PARAMS:
-               ret = ublk_ctrl_set_params(ub, header);
+               ret = ublk_ctrl_set_params(ub, &header);
                break;
        case UBLK_CMD_START_USER_RECOVERY:
-               ret = ublk_ctrl_start_recovery(ub, header);
+               ret = ublk_ctrl_start_recovery(ub, &header);
                break;
        case UBLK_CMD_END_USER_RECOVERY:
-               ret = ublk_ctrl_end_recovery(ub, header);
+               ret = ublk_ctrl_end_recovery(ub, &header);
                break;
        case UBLK_CMD_UPDATE_SIZE:
-               ublk_ctrl_set_size(ub, header);
+               ublk_ctrl_set_size(ub, &header);
                ret = 0;
                break;
        case UBLK_CMD_QUIESCE_DEV:
-               ret = ublk_ctrl_quiesce_dev(ub, header);
+               ret = ublk_ctrl_quiesce_dev(ub, &header);
                break;
        case UBLK_CMD_TRY_STOP_DEV:
                ret = ublk_ctrl_try_stop_dev(ub);
@@ -5302,7 +5308,7 @@ static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,
                ublk_put_device(ub);
  out:
        pr_devel("%s: cmd done ret %d cmd_op %x, dev id %d qid %d\n",
-                       __func__, ret, cmd->cmd_op, header->dev_id, header->queue_id);
+                       __func__, ret, cmd_op, header.dev_id, header.queue_id);
        return ret;
 }