Adding bpf_vma_build_id_parse function to retrieve build id from passed vma object and making it available as bpf kfunc. We can't use build_id_parse directly as kfunc, because we would not have control over the build id buffer size provided by user. Instead we are adding new bpf_vma_build_id_parse function with 'build_id__sz' argument that instructs verifier to check for the available space in build_id buffer. This way we check that there's always available memory space behind build_id pointer. We also check that the build_id__sz is at least BUILD_ID_SIZE_MAX so we can place any buildid in. The bpf_vma_build_id_parse kfunc is marked as KF_TRUSTED_ARGS, so it can be only called with trusted vma objects. These are currently provided only by find_vma callback function and task_vma iterator program. Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx> --- include/linux/bpf.h | 4 ++++ kernel/trace/bpf_trace.c | 31 +++++++++++++++++++++++++++++++ 2 files changed, 35 insertions(+) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index c6aa6912ea16..359c8fe11779 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -2839,4 +2839,8 @@ static inline bool type_is_alloc(u32 type) return type & MEM_ALLOC; } +int bpf_vma_build_id_parse(struct vm_area_struct *vma, + unsigned char *build_id, + size_t build_id__sz); + #endif /* _LINUX_BPF_H */ diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 3bbd3f0c810c..7340de74531a 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -23,6 +23,7 @@ #include <linux/sort.h> #include <linux/key.h> #include <linux/verification.h> +#include <linux/buildid.h> #include <net/bpf_sk_storage.h> @@ -1383,6 +1384,36 @@ static int __init bpf_key_sig_kfuncs_init(void) late_initcall(bpf_key_sig_kfuncs_init); #endif /* CONFIG_KEYS */ +int bpf_vma_build_id_parse(struct vm_area_struct *vma, + unsigned char *build_id, + size_t build_id__sz) +{ + __u32 size; + int err; + + if (build_id__sz < BUILD_ID_SIZE_MAX) + return -EINVAL; + + err = build_id_parse(vma, build_id, &size); + return err ?: (int) size; +} + +BTF_SET8_START(tracing_btf_ids) +BTF_ID_FLAGS(func, bpf_vma_build_id_parse, KF_TRUSTED_ARGS) +BTF_SET8_END(tracing_btf_ids) + +static const struct btf_kfunc_id_set tracing_kfunc_set = { + .owner = THIS_MODULE, + .set = &tracing_btf_ids, +}; + +static int __init kfunc_tracing_init(void) +{ + return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &tracing_kfunc_set); +} + +late_initcall(kfunc_tracing_init); + static const struct bpf_func_proto * bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) { -- 2.38.1