CVE-2026-74371

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

bpf: fix BPFPROGQUERY OOB write and cgroup backward compat

BPFPROGQUERY writes back the 'query.revision' field unconditionally to userspace. If userspace passes a smaller 'bpf_attr' structure (e.g. 40 bytes, which was the layout before the addition of 'query.revision'), the kernel performs an out-of-bounds write.

Fix this by propagating the user-provided attribute size 'uattr_size' down to the cgroup query handlers, and conditionally skipping writing the revision field to userspace when the provided buffer size is insufficient.

query.revision in bpfmprogquery is structurally identical to the cgroup case: a late tail field, written unconditionally.

But the backward-compat hazard is not the same.

The min-historical-size test is per command, and bpfmprogquery only serves attach types that were born with revision in the struct:

• tcxprogquery -> BPFTCXINGRESS/EGRESS
• netkitprogquery -> BPFNETKITPRIMARY/PEER

tcx, netkit, the revision field, and bpfmprogquery itself all landed in the same v6.6 merge window (053c8e1f235d added the mprog query API + revision; tcx in e420bed02507, netkit in 35dfaad7188c). There has never been a tcx/netkit BPFPROGQUERY userspace that doesn't know about revision. So for these commands the minimum legitimate struct already covers offset 56-64 — no old binary can be broken here.

Contrast with cgroup: BPFPROGQUERY on cgroup attach types shipped in 2017; revision write-back was bolted on years later (120933984460). That path has a real population of pre-revision callers.