diff options
| author | Andrii Nakryiko <andrii@kernel.org> | 2021-04-23 21:13:39 +0300 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2021-04-24 00:05:26 +0300 |
| commit | 386b1d241e1b975a239d33be836bc183a52ab18c (patch) | |
| tree | c27ffb88789c8cdb3f0da7dbfcaeaecd7913e239 | |
| parent | 42869d28527695a75346c988ceeedbba7e3880b7 (diff) | |
| download | linux-386b1d241e1b975a239d33be836bc183a52ab18c.tar.xz | |
libbpf: Extend sanity checking ELF symbols with externs validation
Add logic to validate extern symbols, plus some other minor extra checks, like
ELF symbol #0 validation, general symbol visibility and binding validations.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210423181348.1801389-10-andrii@kernel.org
| -rw-r--r-- | tools/lib/bpf/linker.c | 49 |
1 files changed, 40 insertions, 9 deletions
diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c index 1263641e8b97..b0e038480300 100644 --- a/tools/lib/bpf/linker.c +++ b/tools/lib/bpf/linker.c @@ -750,14 +750,45 @@ static int linker_sanity_check_elf_symtab(struct src_obj *obj, struct src_sec *s n = sec->shdr->sh_size / sec->shdr->sh_entsize; sym = sec->data->d_buf; for (i = 0; i < n; i++, sym++) { - if (sym->st_shndx - && sym->st_shndx < SHN_LORESERVE - && sym->st_shndx >= obj->sec_cnt) { + int sym_type = ELF64_ST_TYPE(sym->st_info); + int sym_bind = ELF64_ST_BIND(sym->st_info); + int sym_vis = ELF64_ST_VISIBILITY(sym->st_other); + + if (i == 0) { + if (sym->st_name != 0 || sym->st_info != 0 + || sym->st_other != 0 || sym->st_shndx != 0 + || sym->st_value != 0 || sym->st_size != 0) { + pr_warn("ELF sym #0 is invalid in %s\n", obj->filename); + return -EINVAL; + } + continue; + } + if (sym_bind != STB_LOCAL && sym_bind != STB_GLOBAL && sym_bind != STB_WEAK) { + pr_warn("ELF sym #%d in section #%zu has unsupported symbol binding %d\n", + i, sec->sec_idx, sym_bind); + return -EINVAL; + } + if (sym_vis != STV_DEFAULT && sym_vis != STV_HIDDEN) { + pr_warn("ELF sym #%d in section #%zu has unsupported symbol visibility %d\n", + i, sec->sec_idx, sym_vis); + return -EINVAL; + } + if (sym->st_shndx == 0) { + if (sym_type != STT_NOTYPE || sym_bind == STB_LOCAL + || sym->st_value != 0 || sym->st_size != 0) { + pr_warn("ELF sym #%d is invalid extern symbol in %s\n", + i, obj->filename); + + return -EINVAL; + } + continue; + } + if (sym->st_shndx < SHN_LORESERVE && sym->st_shndx >= obj->sec_cnt) { pr_warn("ELF sym #%d in section #%zu points to missing section #%zu in %s\n", i, sec->sec_idx, (size_t)sym->st_shndx, obj->filename); return -EINVAL; } - if (ELF64_ST_TYPE(sym->st_info) == STT_SECTION) { + if (sym_type == STT_SECTION) { if (sym->st_value != 0) return -EINVAL; continue; @@ -1135,16 +1166,16 @@ static int linker_append_elf_syms(struct bpf_linker *linker, struct src_obj *obj size_t dst_sym_idx; int name_off; - /* we already have all-zero initial symbol */ - if (sym->st_name == 0 && sym->st_info == 0 && - sym->st_other == 0 && sym->st_shndx == SHN_UNDEF && - sym->st_value == 0 && sym->st_size ==0) + /* We already validated all-zero symbol #0 and we already + * appended it preventively to the final SYMTAB, so skip it. + */ + if (i == 0) continue; sym_name = elf_strptr(obj->elf, str_sec_idx, sym->st_name); if (!sym_name) { pr_warn("can't fetch symbol name for symbol #%d in '%s'\n", i, obj->filename); - return -1; + return -EINVAL; } if (sym->st_shndx && sym->st_shndx < SHN_LORESERVE) { |