lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 27 Sep 2021 20:29:36 +0530 From: Kumar Kartikeya Dwivedi <memxor@...il.com> To: bpf@...r.kernel.org Cc: Kumar Kartikeya Dwivedi <memxor@...il.com>, Andrii Nakryiko <andrii@...nel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, Jesper Dangaard Brouer <brouer@...hat.com>, Toke Høiland-Jørgensen <toke@...hat.com>, netdev@...r.kernel.org Subject: [PATCH bpf-next v5 07/12] libbpf: Resolve invalid weak kfunc calls with imm = 0, off = 0 Preserve these calls as it allows verifier to succeed in loading the program if they are determined to be unreachable after dead code elimination during program load. If not, the verifier will fail at runtime. This is done for ext->is_weak symbols similar to the case for variable ksyms. Acked-by: Andrii Nakryiko <andrii@...nel.org> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@...il.com> --- tools/lib/bpf/libbpf.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 0f4d203f926e..4b2d0511c1e7 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -3416,11 +3416,6 @@ static int bpf_object__collect_externs(struct bpf_object *obj) return -ENOTSUP; } } else if (strcmp(sec_name, KSYMS_SEC) == 0) { - if (btf_is_func(t) && ext->is_weak) { - pr_warn("extern weak function %s is unsupported\n", - ext->name); - return -ENOTSUP; - } ksym_sec = sec; ext->type = EXT_KSYM; skip_mods_and_typedefs(obj->btf, t->type, @@ -5369,8 +5364,13 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog) case RELO_EXTERN_FUNC: ext = &obj->externs[relo->sym_off]; insn[0].src_reg = BPF_PSEUDO_KFUNC_CALL; - insn[0].imm = ext->ksym.kernel_btf_id; - insn[0].off = ext->ksym.offset; + if (ext->is_set) { + insn[0].imm = ext->ksym.kernel_btf_id; + insn[0].off = ext->ksym.offset; + } else { /* unresolved weak kfunc */ + insn[0].imm = 0; + insn[0].off = 0; + } break; case RELO_SUBPROG_ADDR: if (insn[0].src_reg != BPF_PSEUDO_FUNC) { @@ -6719,9 +6719,9 @@ static int bpf_object__resolve_ksym_var_btf_id(struct bpf_object *obj, int id, err; id = find_ksym_btf_id(obj, ext->name, BTF_KIND_VAR, &btf, &mod_btf); - if (id == -ESRCH && ext->is_weak) { - return 0; - } else if (id < 0) { + if (id < 0) { + if (id == -ESRCH && ext->is_weak) + return 0; pr_warn("extern (var ksym) '%s': not found in kernel BTF\n", ext->name); return id; @@ -6774,7 +6774,9 @@ static int bpf_object__resolve_ksym_func_btf_id(struct bpf_object *obj, kfunc_id = find_ksym_btf_id(obj, ext->name, BTF_KIND_FUNC, &btf, &mod_btf); if (kfunc_id < 0) { - pr_warn("extern (func ksym) '%s': not found in kernel BTF\n", + if (kfunc_id == -ESRCH && ext->is_weak) + return 0; + pr_warn("extern (func ksym) '%s': not found in kernel or module BTFs\n", ext->name); return kfunc_id; } -- 2.33.0
Powered by blists - more mailing lists