109 lines
4.2 KiB
Diff
109 lines
4.2 KiB
Diff
From 7b5237996a42c3b8a6fe8ccae656047de2831f58 Mon Sep 17 00:00:00 2001
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From: David Vernet <void@manifault.com>
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Date: Wed, 24 Jul 2024 12:14:58 -0500
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Subject: [PATCH] libbpf: Don't take direct pointers into BTF data from st_ops
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In struct bpf_struct_ops, we have take a pointer to a BTF type name, and
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a struct btf_type. This was presumably done for convenience, but can
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actually result in subtle and confusing bugs given that BTF data can be
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invalidated before a program is loaded. For example, in sched_ext, we
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may sometimes resize a data section after a skeleton has been opened,
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but before the struct_ops scheduler map has been loaded. This may cause
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the BTF data to be realloc'd, which can then cause a UAF when loading
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the program because the struct_ops map has pointers directly into the
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BTF data.
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We're already storing the BTF type_id in struct bpf_struct_ops. Because
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type_id is stable, we can therefore just update the places where we were
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looking at those pointers to instead do the lookups we need from the
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type_id.
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Fixes: 590a00888250 ("bpf: libbpf: Add STRUCT_OPS support")
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Signed-off-by: David Vernet <void@manifault.com>
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Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
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Link: https://lore.kernel.org/bpf/20240724171459.281234-1-void@manifault.com
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Conflict:parts of functions do not exist in v0.8.1
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Reference:https://github.com/libbpf/libbpf/commit/7b5237996a42c3b8a6fe8ccae656047de2831f58
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---
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src/libbpf.c | 18 +++++++++---------
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1 file changed, 9 insertions(+), 9 deletions(-)
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diff --git a/src/libbpf.c b/src/libbpf.c
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index 5eb2452..25a91ba 100644
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--- a/src/libbpf.c
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+++ b/src/libbpf.c
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@@ -327,8 +327,6 @@ struct bpf_program {
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};
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struct bpf_struct_ops {
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- const char *tname;
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- const struct btf_type *type;
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struct bpf_program **progs;
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__u32 *kern_func_off;
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/* e.g. struct tcp_congestion_ops in bpf_prog's btf format */
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@@ -955,8 +953,8 @@ static int bpf_map__init_kern_struct_ops(struct bpf_map *map,
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int err;
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st_ops = map->st_ops;
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- type = st_ops->type;
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- tname = st_ops->tname;
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+ type = btf__type_by_id(btf, st_ops->type_id);
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+ tname = btf__name_by_offset(btf, type->name_off);
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err = find_struct_ops_kern_types(kern_btf, tname,
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&kern_type, &kern_type_id,
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&kern_vtype, &kern_vtype_id,
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@@ -1175,8 +1173,6 @@ static int bpf_object__init_struct_ops_maps(struct bpf_object *obj)
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memcpy(st_ops->data,
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obj->efile.st_ops_data->d_buf + vsi->offset,
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type->size);
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- st_ops->tname = tname;
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- st_ops->type = type;
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st_ops->type_id = type_id;
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pr_debug("struct_ops init: struct %s(type_id=%u) %s found at offset %u\n",
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@@ -9361,6 +9357,7 @@ static struct bpf_map *find_struct_ops_map_by_offset(struct bpf_object *obj,
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static int bpf_object__collect_st_ops_relos(struct bpf_object *obj,
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Elf64_Shdr *shdr, Elf_Data *data)
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{
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+ const struct btf_type *type;
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const struct btf_member *member;
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struct bpf_struct_ops *st_ops;
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struct bpf_program *prog;
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@@ -9420,13 +9417,14 @@ static int bpf_object__collect_st_ops_relos(struct bpf_object *obj,
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}
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insn_idx = sym->st_value / BPF_INSN_SZ;
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- member = find_member_by_offset(st_ops->type, moff * 8);
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+ type = btf__type_by_id(btf, st_ops->type_id);
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+ member = find_member_by_offset(type, moff * 8);
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if (!member) {
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pr_warn("struct_ops reloc %s: cannot find member at moff %u\n",
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map->name, moff);
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return -EINVAL;
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}
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- member_idx = member - btf_members(st_ops->type);
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+ member_idx = member - btf_members(type);
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name = btf__name_by_offset(btf, member->name_off);
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if (!resolve_func_ptr(btf, member->type, NULL)) {
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@@ -11967,6 +11965,7 @@ static int bpf_link__detach_struct_ops(struct bpf_link *link)
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struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
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{
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+ const struct btf_type *type;
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struct bpf_struct_ops *st_ops;
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struct bpf_link *link;
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__u32 i, zero = 0;
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@@ -11980,7 +11979,8 @@ struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
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return libbpf_err_ptr(-EINVAL);
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st_ops = map->st_ops;
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- for (i = 0; i < btf_vlen(st_ops->type); i++) {
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+ type = btf__type_by_id(map->obj->btf, st_ops->type_id);
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+ for (i = 0; i < btf_vlen(type); i++) {
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struct bpf_program *prog = st_ops->progs[i];
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void *kern_data;
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int prog_fd;
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--
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2.33.0
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