CVE-2026-74371bpf: fix BPF_PROG_QUERY OOB write and cgroup backward compat

Official description

In the Linux kernel, the following vulnerability has been resolved: bpf: fix BPF_PROG_QUERY OOB write and cgroup backward compat BPF_PROG_QUERY 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 bpf_mprog_query 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 bpf_mprog_query only serves attach types that were born with revision in the struct: - tcx_prog_query -> BPF_TCX_INGRESS/EGRESS - netkit_prog_query -> BPF_NETKIT_PRIMARY/PEER tcx, netkit, the revision field, and bpf_mprog_query 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 BPF_PROG_QUERY 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: BPF_PROG_QUERY 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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/b78eb6efbf052d44a3a14726aa7c7d5aa2e544d7
• https://git.kernel.org/stable/c/a7131340d0f95df9a541257dccab5d85e6bcdd2b
• https://git.kernel.org/stable/c/d3d630e8a7f3421bc2d204b87bdff35b4432a8e3
• https://git.kernel.org/stable/c/21c4b99b27f3f85b89256e81b3e997dec0a460d0