CVE-2026-43364ublk: fix NULL pointer dereference in ublk_ctrl_set_size()

Official description

In the Linux kernel, the following vulnerability has been resolved: ublk: fix NULL pointer dereference in ublk_ctrl_set_size() ublk_ctrl_set_size() unconditionally dereferences ub->ub_disk via set_capacity_and_notify() without checking if it is NULL. ub->ub_disk is NULL before UBLK_CMD_START_DEV completes (it is only assigned in ublk_ctrl_start_dev()) and after UBLK_CMD_STOP_DEV runs (ublk_detach_disk() sets it to NULL). Since the UBLK_CMD_UPDATE_SIZE handler performs no state validation, a user can trigger a NULL pointer dereference by sending UPDATE_SIZE to a device that has been added but not yet started, or one that has been stopped. Fix this by checking ub->ub_disk under ub->mutex before dereferencing it, and returning -ENODEV if the disk is not available.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/f13fe6794726755a43090cb680c4c58cea6aa5f1
• https://git.kernel.org/stable/c/c28d945bfa92e15147e93b73f95345b9bec979b0
• https://git.kernel.org/stable/c/25966fc097691e5c925ad080f64a2f19c5fd940a