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bpf: Remove tracing program restriction on map types

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The hash map is now fully converted to bpf_mem_alloc. Its implementation is not
allocating synchronously and not calling call_rcu() directly. It's now safe to
use non-preallocated hash maps in all types of tracing programs including
BPF_PROG_TYPE_PERF_EVENT that runs out of NMI context.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220902211058.60789-13-alexei.starovoitov@gmail.com
This commit is contained in:
Alexei Starovoitov 2022-09-02 14:10:54 -07:00 committed by Daniel Borkmann
parent ee4ed53c5e
commit 96da3f7d48
1 changed files with 0 additions and 42 deletions
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42
kernel/bpf/verifier.c
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@ -12623,48 +12623,6 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
{
enum bpf_prog_type prog_type = resolve_prog_type(prog);
/*
* Validate that trace type programs use preallocated hash maps.
*
* For programs attached to PERF events this is mandatory as the
* perf NMI can hit any arbitrary code sequence.
*
* All other trace types using non-preallocated per-cpu hash maps are
* unsafe as well because tracepoint or kprobes can be inside locked
* regions of the per-cpu memory allocator or at a place where a
* recursion into the per-cpu memory allocator would see inconsistent
* state. Non per-cpu hash maps are using bpf_mem_alloc-tor which is
* safe to use from kprobe/fentry and in RT.
*
* On RT enabled kernels run-time allocation of all trace type
* programs is strictly prohibited due to lock type constraints. On
* !RT kernels it is allowed for backwards compatibility reasons for
* now, but warnings are emitted so developers are made aware of
* the unsafety and can fix their programs before this is enforced.
*/
if (is_tracing_prog_type(prog_type) && !is_preallocated_map(map)) {
if (prog_type == BPF_PROG_TYPE_PERF_EVENT) {
/* perf_event bpf progs have to use preallocated hash maps
* because non-prealloc is still relying on call_rcu to free
* elements.
*/
verbose(env, "perf_event programs can only use preallocated hash map\n");
return -EINVAL;
}
if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
(map->inner_map_meta &&
map->inner_map_meta->map_type == BPF_MAP_TYPE_PERCPU_HASH)) {
if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
verbose(env,
"trace type programs can only use preallocated per-cpu hash map\n");
return -EINVAL;
}
WARN_ONCE(1, "trace type BPF program uses run-time allocation\n");
verbose(env,
"trace type programs with run-time allocated per-cpu hash maps are unsafe."
" Switch to preallocated hash maps.\n");
}
}
if (map_value_has_spin_lock(map)) {
if (prog_type == BPF_PROG_TYPE_SOCKET_FILTER) {