GHSA-C3CF-VCGJ-VRGP
Vulnerability from github – Published: 2026-09-16 12:30 – Updated: 2026-09-16 15:31In the Linux kernel, the following vulnerability has been resolved:
media: cx231xx: reject geometry changes while the VBI queue is busy
vidioc_s_fmt_vid_cap() and vidioc_s_std() change the device-wide dev->width / dev->norm but only refuse the change when the video queue (dev->vidq) is busy. The VBI queue (dev->vbiq) shares that same geometry: cx231xx_init_vbi_isoc() latches dma_q->lines_per_field from dev->norm, the VBI videobuf2 plane is sized from dev->width / dev->norm in vbi_queue_setup() and vbi_buf_prepare(), and cx231xx_do_vbi_copy() then recomputes the destination offset from the live dev->width and the latched lines_per_field on every URB completion:
offset = lines_completed * (dev->width << 1) + ...;
if (dma_q->current_field == 2)
offset += dev->width * 2 * dma_q->lines_per_field;
memcpy(plane + offset, p_buffer, lencopy);
Because the VBI node shares video_ioctl_ops with the video node, an application can size a small VBI plane (REQBUFS/QBUF with a small width, or with the NTSC standard), then enlarge dev->width (or switch dev->norm to PAL) through the video node while the VBI stream is running -- the change is allowed because only dev->vidq is checked -- and let the device deliver a field-2 VBI payload. cx231xx_do_vbi_copy() now computes the offset with the larger geometry and memcpy()s past the end of the smaller plane that was already allocated, a heap out-of-bounds write whose offset is attacker-chosen and whose contents come from the device. The per-field guard in cx231xx_copy_vbi_line() does not help: it bounds the copy against the latched lines_per_field, not the plane's real capacity, and vb2 does not re-run buf_prepare() for an already prepared buffer.
Refuse the format/standard change when the VBI queue is busy as well, so the geometry cannot change underneath an allocated VBI buffer.
{
"affected": [],
"aliases": [
"CVE-2026-89894"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-16T11:16:58Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmedia: cx231xx: reject geometry changes while the VBI queue is busy\n\nvidioc_s_fmt_vid_cap() and vidioc_s_std() change the device-wide\ndev-\u003ewidth / dev-\u003enorm but only refuse the change when the *video* queue\n(dev-\u003evidq) is busy. The VBI queue (dev-\u003evbiq) shares that same geometry:\ncx231xx_init_vbi_isoc() latches dma_q-\u003elines_per_field from dev-\u003enorm,\nthe VBI videobuf2 plane is sized from dev-\u003ewidth / dev-\u003enorm in\nvbi_queue_setup() and vbi_buf_prepare(), and cx231xx_do_vbi_copy() then\nrecomputes the destination offset from the *live* dev-\u003ewidth and the\nlatched lines_per_field on every URB completion:\n\n\toffset = lines_completed * (dev-\u003ewidth \u003c\u003c 1) + ...;\n\tif (dma_q-\u003ecurrent_field == 2)\n\t\toffset += dev-\u003ewidth * 2 * dma_q-\u003elines_per_field;\n\tmemcpy(plane + offset, p_buffer, lencopy);\n\nBecause the VBI node shares video_ioctl_ops with the video node, an\napplication can size a small VBI plane (REQBUFS/QBUF with a small width,\nor with the NTSC standard), then enlarge dev-\u003ewidth (or switch dev-\u003enorm\nto PAL) through the video node while the VBI stream is running -- the\nchange is allowed because only dev-\u003evidq is checked -- and let the device\ndeliver a field-2 VBI payload. cx231xx_do_vbi_copy() now computes the\noffset with the larger geometry and memcpy()s past the end of the smaller\nplane that was already allocated, a heap out-of-bounds write whose offset\nis attacker-chosen and whose contents come from the device. The\nper-field guard in cx231xx_copy_vbi_line() does not help: it bounds the\ncopy against the latched lines_per_field, not the plane\u0027s real capacity,\nand vb2 does not re-run buf_prepare() for an already prepared buffer.\n\nRefuse the format/standard change when the VBI queue is busy as well, so\nthe geometry cannot change underneath an allocated VBI buffer.",
"id": "GHSA-c3cf-vcgj-vrgp",
"modified": "2026-09-16T15:31:00Z",
"published": "2026-09-16T12:30:40Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89894"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1d1079db8d1807e259a1d2679ed314949797aad9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/54ac6df8b8d97eddc3ae97fd2045bdedc8541b6d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/627a121c15fe05a541f44d86016294b80bada75d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7087bef6510c7df5df0b19192633b8ecc0f33a6f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/90d50648af36a1fbf5dbc99238de6fd0e58a13e0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a5dd3d7fba358ff9486f3f51b2a9038348c0970a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a636c72c7f522d984fa498fc0631f33a2d0be3fd"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/aa3314506deb9703bcf0e889db08959440228fbf"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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