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So let's warn on it. >> >> Please extend raw_tracepoint to other attach types which >> may cause runtime map allocations. >> > > Per my understanding, it is safe to allocate memory in a non-process > context as long as we don't allow blocking it. > So this issue doesn't matter with whether it causes runtime map > allocations or not, while it really matters with the tracepoint or > kprobe. > Regarding the tracepoint or kprobe, if we don't use non-preallocated > maps, it may allocate other extra memory besides the map element > itself. > I have verified that it is safe to use non-preallocated maps in > BPF_TRACE_ITER or BPF_TRACE_FENTRY. > So filtering out BPF_TRACE_RAW_TP only is enough. > >>> >>> Signed-off-by: Yafang Shao >>> --- >>> kernel/bpf/verifier.c | 18 +++++++++++++----- >>> 1 file changed, 13 insertions(+), 5 deletions(-) >>> >>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c >>> index e3cf6194c24f..3cd8260827e0 100644 >>> --- a/kernel/bpf/verifier.c >>> +++ b/kernel/bpf/verifier.c >>> @@ -12574,14 +12574,20 @@ static int check_map_prealloc(struct bpf_map *map) >>> !(map->map_flags & BPF_F_NO_PREALLOC); >>> } >>> >>> -static bool is_tracing_prog_type(enum bpf_prog_type type) >>> +static bool is_tracing_prog_type(enum bpf_prog_type prog_type, >>> + enum bpf_attach_type attach_type) >>> { >>> - switch (type) { >>> + switch (prog_type) { >>> case BPF_PROG_TYPE_KPROBE: >>> case BPF_PROG_TYPE_TRACEPOINT: >>> case BPF_PROG_TYPE_PERF_EVENT: >>> case BPF_PROG_TYPE_RAW_TRACEPOINT: >>> + case BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE: >>> return true; >>> + case BPF_PROG_TYPE_TRACING: >>> + if (attach_type == BPF_TRACE_RAW_TP) >>> + return true; >> >> As Alexei mentioned earlier, here we should have >> if (attach_type != BPF_TRACE_ITER) >> return true; > > That will break selftests/bpf/progs/timer.c, because it uses timer in fentry. Okay. Let us remove BPF_PROG_TYPE_TRACING from this patch for now. fentry/fexit/fmod may attach any kallsyms functions and many of them are called in process context and non-preallocated hashmap totally fine. It is not good to prohibit non-preallocated hashmap for any fentry/fexit/fmod bpf programs. > >> For attach types with BPF_PROG_TYPE_TRACING programs, >> BPF_TRACE_ITER attach type can only appear in process context. >> All other attach types may appear in non-process context. >> > > Thanks for the explanation. > >>> + return false; >>> default: >>> return false; >>> } >>> @@ -12601,7 +12607,9 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env, >>> struct bpf_prog *prog) >>> >>> { >>> + enum bpf_attach_type attach_type = prog->expected_attach_type; >>> enum bpf_prog_type prog_type = resolve_prog_type(prog); >>> + >> [...] > > >