CVE-2026-98007: bpf: Reject non-scalar bpf_loop iteration counts

CVE-2026-98007: bpf: Reject non-scalar bpf_loop iteration counts

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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

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

bpf: Reject non-scalar bpf_loop iteration counts

bpf_loop() declares its nr_loops argument as ARG_ANYTHING. Privileged
programs may pass pointer values to such arguments, so check_func_arg()
lets a pointer-valued R1 reach the helper-specific checks.

Since commit bb124da69c47 ("bpf: keep track of max number of bpf_loop
callback iterations"), the verifier marks R1 precise and reads its upper
bound to limit callback simulation. Precision backtracking only accepts
scalar registers, so passing a pointer instead triggers the "backtracking
misuse" verifier warning. Kernels with panic_on_warn enabled subsequently
panic.

Introduce ARG_SCALAR for helper arguments that only accept scalar values
and use it for bpf_loop() nr_loops. Generic helper argument validation then
rejects pointers before loop inlining and precision processing.

The Linux kernel CVE team has assigned CVE-2026-98007 to this issue.


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

	Issue introduced in 6.7 with commit bb124da69c47dd98d69361ec13244ece50bec63e and fixed in 6.12.111 with commit 656d40d1ca228ee21a9b3280432479fc9eae75ab
	Issue introduced in 6.7 with commit bb124da69c47dd98d69361ec13244ece50bec63e and fixed in 6.18.53 with commit e2e1161e03fecff6d2229a81b024337144bfcd97
	Issue introduced in 6.7 with commit bb124da69c47dd98d69361ec13244ece50bec63e and fixed in 7.2.7 with commit f8ae8275c721334ee50fafdd986fb83294eb941a
	Issue introduced in 6.7 with commit bb124da69c47dd98d69361ec13244ece50bec63e and fixed in 7.3-rc2 with commit c3fd8e5fd100f122bad503bdc0e9277219533253
	Issue introduced in 6.6.15 with commit bfc5c19b4b48840627af0d0f1c8f4461b276e508

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-2026-98007
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:
	include/linux/bpf.h
	kernel/bpf/bpf_iter.c
	kernel/bpf/verifier.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/656d40d1ca228ee21a9b3280432479fc9eae75ab
	https://git.kernel.org/stable/c/e2e1161e03fecff6d2229a81b024337144bfcd97
	https://git.kernel.org/stable/c/f8ae8275c721334ee50fafdd986fb83294eb941a
	https://git.kernel.org/stable/c/c3fd8e5fd100f122bad503bdc0e9277219533253