From: Andrii Nakryiko <andrii@kernel.org>
To: <bpf@vger.kernel.org>, <netdev@vger.kernel.org>, <ast@fb.com>,
<daniel@iogearbox.net>
Cc: <andrii@kernel.org>, <kernel-team@fb.com>
Subject: [PATCH bpf-next 09/17] libbpf: extend sanity checking ELF symbols with externs validation
Date: Wed, 14 Apr 2021 13:01:38 -0700 [thread overview]
Message-ID: <20210414200146.2663044-10-andrii@kernel.org> (raw)
In-Reply-To: <20210414200146.2663044-1-andrii@kernel.org>
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>
---
tools/lib/bpf/linker.c | 43 +++++++++++++++++++++++++++++++++---------
1 file changed, 34 insertions(+), 9 deletions(-)
diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
index b23bfa6e7e5f..dc202a5d8235 100644
--- a/tools/lib/bpf/linker.c
+++ b/tools/lib/bpf/linker.c
@@ -752,14 +752,39 @@ 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);
+
+ 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 is section #%zu has unsupported symbol binding %d\n",
+ i, sec->sec_idx, sym_bind);
+ 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;
@@ -1137,16 +1162,16 @@ 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) {
--
2.30.2
next prev parent reply other threads:[~2021-04-14 20:02 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-14 20:01 [PATCH bpf-next 00/17] BPF static linker: support externs Andrii Nakryiko
2021-04-14 20:01 ` [PATCH bpf-next 01/17] bpftool: support dumping BTF VAR's "extern" linkage Andrii Nakryiko
2021-04-14 20:01 ` [PATCH bpf-next 02/17] bpftool: dump more info about DATASEC members Andrii Nakryiko
2021-04-14 20:01 ` [PATCH bpf-next 03/17] libbpf: suppress compiler warning when using SEC() macro with externs Andrii Nakryiko
2021-04-14 20:01 ` [PATCH bpf-next 04/17] libbpf: mark BPF subprogs with hidden visibility as static for BPF verifier Andrii Nakryiko
2021-04-14 20:01 ` [PATCH bpf-next 05/17] libbpf: allow gaps in BPF program sections to support overriden weak functions Andrii Nakryiko
2021-04-14 20:01 ` [PATCH bpf-next 06/17] libbpf: refactor BTF map definition parsing Andrii Nakryiko
2021-04-14 20:01 ` [PATCH bpf-next 07/17] libbpf: factor out symtab and relos sanity checks Andrii Nakryiko
2021-04-14 20:01 ` [PATCH bpf-next 08/17] libbpf: make few internal helpers available outside of libbpf.c Andrii Nakryiko
2021-04-14 20:01 ` Andrii Nakryiko [this message]
2021-04-14 20:01 ` [PATCH bpf-next 10/17] libbpf: tighten BTF type ID rewriting with error checking Andrii Nakryiko
2021-04-14 20:01 ` [PATCH bpf-next 11/17] libbpf: add linker extern resolution support for functions and global variables Andrii Nakryiko
2021-04-14 20:01 ` [PATCH bpf-next 12/17] libbpf: support extern resolution for BTF-defined maps in .maps section Andrii Nakryiko
2021-04-14 22:00 ` Alexei Starovoitov
2021-04-14 23:48 ` Andrii Nakryiko
2021-04-15 2:01 ` Alexei Starovoitov
2021-04-15 20:35 ` Andrii Nakryiko
2021-04-15 20:57 ` Alexei Starovoitov
2021-04-14 20:01 ` [PATCH bpf-next 13/17] selftests/bpf: use -O0 instead of -Og in selftests builds Andrii Nakryiko
2021-04-14 22:02 ` Alexei Starovoitov
2021-04-14 22:15 ` David Laight
2021-04-15 0:03 ` Andrii Nakryiko
2021-04-14 20:01 ` [PATCH bpf-next 14/17] selftests/bpf: omit skeleton generation for multi-linked BPF object files Andrii Nakryiko
2021-04-14 20:01 ` [PATCH bpf-next 15/17] selftests/bpf: add function linking selftest Andrii Nakryiko
2021-04-14 20:01 ` [PATCH bpf-next 16/17] selftests/bpf: add global variables " Andrii Nakryiko
2021-04-14 20:01 ` [PATCH bpf-next 17/17] sleftests/bpf: add map " Andrii Nakryiko
2021-04-15 0:21 ` [PATCH bpf-next 00/17] BPF static linker: support externs Andrii Nakryiko
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