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6fcd486b3a
bpf_rcu_read_lock/unlock() are only available in clang compiled kernels. Lack of such key mechanism makes it impossible for sleepable bpf programs to use RCU pointers. Allow bpf_rcu_read_lock/unlock() in GCC compiled kernels (though GCC doesn't support btf_type_tag yet) and allowlist certain field dereferences in important data structures like tast_struct, cgroup, socket that are used by sleepable programs either as RCU pointer or full trusted pointer (which is valid outside of RCU CS). Use BTF_TYPE_SAFE_RCU and BTF_TYPE_SAFE_TRUSTED macros for such tagging. They will be removed once GCC supports btf_type_tag. With that refactor check_ptr_to_btf_access(). Make it strict in enforcing PTR_TRUSTED and PTR_UNTRUSTED while deprecating old PTR_TO_BTF_ID without modifier flags. There is a chance that this strict enforcement might break existing programs (especially on GCC compiled kernels), but this cleanup has to start sooner than later. Note PTR_TO_CTX access still yields old deprecated PTR_TO_BTF_ID. Once it's converted to strict PTR_TRUSTED or PTR_UNTRUSTED the kfuncs and helpers will be able to default to KF_TRUSTED_ARGS. KF_RCU will remain as a weaker version of KF_TRUSTED_ARGS where obj refcnt could be 0. Adjust rcu_read_lock selftest to run on gcc and clang compiled kernels. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230303041446.3630-7-alexei.starovoitov@gmail.com
126 lines
2.8 KiB
C
126 lines
2.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
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#include <vmlinux.h>
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#include <bpf/bpf_tracing.h>
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#include <bpf/bpf_helpers.h>
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#include "bpf_misc.h"
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#include "cpumask_common.h"
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char _license[] SEC("license") = "GPL";
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/* Prototype for all of the program trace events below:
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*
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* TRACE_EVENT(task_newtask,
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* TP_PROTO(struct task_struct *p, u64 clone_flags)
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*/
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SEC("tp_btf/task_newtask")
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__failure __msg("Unreleased reference")
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int BPF_PROG(test_alloc_no_release, struct task_struct *task, u64 clone_flags)
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{
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struct bpf_cpumask *cpumask;
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cpumask = create_cpumask();
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/* cpumask is never released. */
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return 0;
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}
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SEC("tp_btf/task_newtask")
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__failure __msg("NULL pointer passed to trusted arg0")
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int BPF_PROG(test_alloc_double_release, struct task_struct *task, u64 clone_flags)
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{
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struct bpf_cpumask *cpumask;
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cpumask = create_cpumask();
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/* cpumask is released twice. */
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bpf_cpumask_release(cpumask);
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bpf_cpumask_release(cpumask);
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return 0;
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}
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SEC("tp_btf/task_newtask")
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__failure __msg("must be referenced")
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int BPF_PROG(test_acquire_wrong_cpumask, struct task_struct *task, u64 clone_flags)
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{
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struct bpf_cpumask *cpumask;
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/* Can't acquire a non-struct bpf_cpumask. */
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cpumask = bpf_cpumask_acquire((struct bpf_cpumask *)task->cpus_ptr);
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return 0;
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}
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SEC("tp_btf/task_newtask")
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__failure __msg("bpf_cpumask_set_cpu args#1 expected pointer to STRUCT bpf_cpumask")
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int BPF_PROG(test_mutate_cpumask, struct task_struct *task, u64 clone_flags)
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{
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struct bpf_cpumask *cpumask;
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/* Can't set the CPU of a non-struct bpf_cpumask. */
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bpf_cpumask_set_cpu(0, (struct bpf_cpumask *)task->cpus_ptr);
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return 0;
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}
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SEC("tp_btf/task_newtask")
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__failure __msg("Unreleased reference")
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int BPF_PROG(test_insert_remove_no_release, struct task_struct *task, u64 clone_flags)
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{
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struct bpf_cpumask *cpumask;
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struct __cpumask_map_value *v;
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cpumask = create_cpumask();
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if (!cpumask)
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return 0;
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if (cpumask_map_insert(cpumask))
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return 0;
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v = cpumask_map_value_lookup();
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if (!v)
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return 0;
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cpumask = bpf_kptr_xchg(&v->cpumask, NULL);
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/* cpumask is never released. */
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return 0;
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}
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SEC("tp_btf/task_newtask")
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__failure __msg("Unreleased reference")
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int BPF_PROG(test_kptr_get_no_release, struct task_struct *task, u64 clone_flags)
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{
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struct bpf_cpumask *cpumask;
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struct __cpumask_map_value *v;
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cpumask = create_cpumask();
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if (!cpumask)
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return 0;
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if (cpumask_map_insert(cpumask))
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return 0;
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v = cpumask_map_value_lookup();
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if (!v)
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return 0;
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cpumask = bpf_cpumask_kptr_get(&v->cpumask);
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/* cpumask is never released. */
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return 0;
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}
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SEC("tp_btf/task_newtask")
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__failure __msg("NULL pointer passed to trusted arg0")
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int BPF_PROG(test_cpumask_null, struct task_struct *task, u64 clone_flags)
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{
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/* NULL passed to KF_TRUSTED_ARGS kfunc. */
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bpf_cpumask_empty(NULL);
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return 0;
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}
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