CVE-2026-64293

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

iommufd: Use sizeof(*hdr) instead of sizeof(hdr) in veventq read

The bound-check in iommufd_veventq_fops_read() for the normal vEVENT

path uses sizeof(hdr) where the surrounding code uses sizeof(*hdr):

if (!vevent_for_lost_events_header(cur) &&

sizeof(hdr) + cur->data_len > count - done) {

hdr is declared as struct iommufd_vevent_header *, so sizeof(hdr)

evaluates to the size of the pointer. Surrounding code uses

sizeof(*hdr) consistently:

if (done >= count || sizeof(*hdr) > count - done) {

...

if (copy_to_user(buf + done, hdr, sizeof(*hdr))) {

...

done += sizeof(*hdr);

struct iommufd_vevent_header is currently 8 bytes (two __u32 fields,

flags and sequence), so on 64-bit (sizeof(void *) == 8) the two

expressions happen to be equal and the check works as intended.

On 32-bit (sizeof(void *) == 4) the check under-counts the header by

4 bytes: a vEVENT whose data_len causes 8 + cur->data_len to exceed

co

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References