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, 34 insertions, 0 deletions

diff --git a/Documentation/admin-guide/sysctl/abi.rst b/Documentation/admin-guide/sysctl/abi.rst
new file mode 100644
index 000000000..4e6db0a2a
--- /dev/null
+++ b/Documentation/admin-guide/sysctl/abi.rst
@@ -0,0 +1,34 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+================================
+Documentation for /proc/sys/abi/
+================================
+
+.. See scripts/check-sysctl-docs to keep this up to date:
+.. scripts/check-sysctl-docs -vtable="abi" \
+..         Documentation/admin-guide/sysctl/abi.rst \
+..         $(git grep -l register_sysctl_)
+
+Copyright (c) 2020, Stephen Kitt
+
+For general info, see Documentation/admin-guide/sysctl/index.rst.
+
+------------------------------------------------------------------------------
+
+The files in ``/proc/sys/abi`` can be used to see and modify
+ABI-related settings.
+
+Currently, these files might (depending on your configuration)
+show up in ``/proc/sys/kernel``:
+
+.. contents:: :local:
+
+vsyscall32 (x86)
+================
+
+Determines whether the kernels maps a vDSO page into 32-bit processes;
+can be set to 1 to enable, or 0 to disable. Defaults to enabled if
+``CONFIG_COMPAT_VDSO`` is set, disabled otherwise.
+
+This controls the same setting as the ``vdso32`` kernel boot
+parameter.