CVE-2026-72112: io_uring/bpf-ops: reject re-registration of an already-bound ops

From: Greg Kroah-Hartman <[email protected]>

Description
===========

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

io_uring/bpf-ops: reject re-registration of an already-bound ops

io_install_bpf() only rejects a second registration on the ctx side
(ctx->bpf_ops) and sets the per-map back-pointer ops->priv
unconditionally. The struct_ops link path never advances a map past
BPF_STRUCT_OPS_STATE_READY, so the same io_uring_bpf_ops map can be
registered more than once, and bpf_io_reg() re-resolves the target ring
via fget(ops->ring_fd) on every call. A caller can therefore point the
same ring_fd at a different io_ring_ctx between two BPF_LINK_CREATE
calls.

The second registration passes the ctx->bpf_ops check (the new ctx has
none) and overwrites ops->priv, orphaning the first ctx. Teardown
(io_eject_bpf()/bpf_io_unreg()) only reaches a ctx through ops->priv, so
the orphaned ctx is never torn down: its ctx->loop_step keeps pointing
into the struct_ops trampoline, which is freed once the map is gone. A
later io_uring_enter() on the orphaned ring then calls the dangling
ctx->loop_step from io_run_loop() -- a use-after-free of freed
executable memory, reachable by a task with CAP_BPF + CAP_PERFMON.

Reject registration when ops->priv is already set, as hid_bpf_reg()
does for its struct_ops.

The Linux kernel CVE team has assigned CVE-2026-72112 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 7.1 with commit 98f37634b12b17ad5c56db8fb63cf9d7dc55d74c and fixed in 7.1.5 with commit 0639ea767fe04c288a8d6cb826100fe3d95d4936
	Issue introduced in 7.1 with commit 98f37634b12b17ad5c56db8fb63cf9d7dc55d74c and fixed in 7.2-rc4 with commit 3afc64c61ce906a04f073ca350b46de10e8302f9

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-72112
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	io_uring/bpf-ops.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/0639ea767fe04c288a8d6cb826100fe3d95d4936
	https://git.kernel.org/stable/c/3afc64c61ce906a04f073ca350b46de10e8302f9