CVE-2026-43364

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