From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- Documentation/admin-guide/sysctl/crypto.rst | 83 +++++++++++++++++++++++++++++ 1 file changed, 83 insertions(+) create mode 100644 Documentation/admin-guide/sysctl/crypto.rst (limited to 'Documentation/admin-guide/sysctl/crypto.rst') diff --git a/Documentation/admin-guide/sysctl/crypto.rst b/Documentation/admin-guide/sysctl/crypto.rst new file mode 100644 index 000000000..9a1bd5328 --- /dev/null +++ b/Documentation/admin-guide/sysctl/crypto.rst @@ -0,0 +1,83 @@ +================= +/proc/sys/crypto/ +================= + +These files show up in ``/proc/sys/crypto/``, depending on the +kernel configuration: + +.. contents:: :local: + +.. _af_alg_restrict: + +af_alg_restrict +=============== + +Controls the level of restriction of AF_ALG. + +AF_ALG is a deprecated and rarely-used userspace interface that is a +frequent source of vulnerabilities. It also unnecessarily exposes a +large number of kernel implementation details. For more information +about AF_ALG, see :ref:`Documentation/crypto/userspace-if.rst +`. + +Starting in Linux v7.3, AF_ALG supports only a limited set of +algorithms by default. This sysctl allows the system administrator to +remove this restriction when needed for compatibility reasons, or to +go further and disable AF_ALG entirely. The default value is 1. + +=== ================================================================== +0 AF_ALG is unrestricted. + +1 AF_ALG is supported with a limited list of algorithms. The list + is designed for compatibility with known users such as iwd and + bluez that haven't yet been fixed to use userspace crypto code. + + Specifically, there is an allowlist for unprivileged processes + and a somewhat longer allowlist for processes that hold + CAP_SYS_ADMIN or CAP_NET_ADMIN in the initial user namespace. + + Attempts to bind() an AF_ALG socket with a disallowed algorithm + fail with ENOENT. + +2 AF_ALG is completely disabled. Attempts to create an AF_ALG + socket fail with EAFNOSUPPORT. +=== ================================================================== + +fips_enabled +============ + +Read-only flag that indicates whether FIPS mode is enabled. + +- ``0``: FIPS mode is disabled (default). +- ``1``: FIPS mode is enabled. + +This value is set at boot time via the ``fips=1`` kernel command line +parameter. When enabled, the cryptographic API will restrict the use +of certain algorithms and perform self-tests to ensure compliance with +FIPS (Federal Information Processing Standards) requirements, such as +FIPS 140-2 and the newer FIPS 140-3, depending on the kernel +configuration and the module in use. + +fips_name +========= + +Read-only file that contains the name of the FIPS module currently in use. +The value is typically configured via the ``CONFIG_CRYPTO_FIPS_NAME`` +kernel configuration option. + +fips_version +============ + +Read-only file that contains the version string of the FIPS module. +If ``CONFIG_CRYPTO_FIPS_CUSTOM_VERSION`` is set, it uses the value from +``CONFIG_CRYPTO_FIPS_VERSION``. Otherwise, it defaults to the kernel +release version (``UTS_RELEASE``). + +Copyright (c) 2026, Shubham Chakraborty + +For general info and legal blurb, please look in +Documentation/admin-guide/sysctl/index.rst. + +.. See scripts/check-sysctl-docs to keep this up to date: +.. scripts/check-sysctl-docs -vtable="crypto" \ +.. $(git grep -l register_sysctl_) -- cgit v1.3.1