bpf: mark a NULL kfunc argument precisegrafted

check_kfunc_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

Fixes: 3bda08b63670 ("bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-5-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 83 insertions, 0 deletions

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
+<crypto_userspace_interface>`.
+
+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 <chakrabortyshubham66@gmail.com>
+
+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_)