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CVE-2026-99063

dm ioctl: don't let data_start run past the buffer PUBLISHED

Description (CNA)

In the Linux kernel, the following vulnerability has been resolved: dm ioctl: don't let data_start run past the buffer struct dm_ioctl has seven bytes of trailing padding, so the smallest buffer userspace is allowed to ask for, offsetof(struct dm_ioctl, data), is seven bytes shorter than sizeof(struct dm_ioctl). get_result_buffer() sets data_start to sizeof(struct dm_ioctl) without looking at how big the buffer actually is. Ask for the minimum and data_start ends up seven bytes past the end. Callers add it to data_size, and ctl_ioctl() copies that much back to userspace: BUG: KASAN: slab-out-of-bounds in _copy_to_user+0xad/0xd0 Read of size 312 at addr ffff8880169e4c00 by task repro-dm/140 ctl_ioctl+0x5e3/0xcb0 dm_ctl_ioctl+0x25/0x40 allocated 305-byte region [ffff8880169e4c00, ffff8880169e4d31) A DM_LIST_DEVICES with data_size set to 305 is enough to hit it, and the seven bytes that leak are whatever sat next to the allocation. Clamp data_start to the buffer size. Note that this is not a security bug because the out-of-bounds read can only be triggered by root.

Affected (CNA)

Vendor / productVersions
Linux / Linuxaffected 76c072b48e39e9291fbf02d6c912cf27d65e093d before 98195e822343a656b92e235847ab3e72b1a3f920; affected 76c072b48e39e9291fbf02d6c912cf27d65e093d before e5c3f3d8935ecc64c962fb66e6a86dbf79218f61; affected 76c072b48e39e9291fbf02d6c912cf27d65e093d before 5680b6fb3054677d4ee65d3baba24b649f1b430e; affected 76c072b48e39e9291fbf02d6c912cf27d65e093d before 725b49c689bbb29ef740b0d6b5ea9390baa9a695; affected 76c072b48e39e9291fbf02d6c912cf27d65e093d before 9b3fcf519d370df94a56f3b272d9eddffffa5be8
Linux / Linuxaffected 2.6.25; unaffected 0 before 2.6.25; unaffected 6.6.160 through 6.6.*; unaffected 6.12.113 through 6.12.*; unaffected 6.18.57 through 6.18.*; unaffected 7.2.11 through 7.2.*; unaffected 7.3 through *

CWE

No CWE identifiers supplied.

References