6.11-stable review patch. If anyone has any objections, please let me know.
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From: David Vernet void@manifault.com
[ Upstream commit 04a94133f1b3cccb19e056c26f056c50b4e5b3b1 ]
In struct bpf_struct_ops, we have take a pointer to a BTF type name, and a struct btf_type. This was presumably done for convenience, but can actually result in subtle and confusing bugs given that BTF data can be invalidated before a program is loaded. For example, in sched_ext, we may sometimes resize a data section after a skeleton has been opened, but before the struct_ops scheduler map has been loaded. This may cause the BTF data to be realloc'd, which can then cause a UAF when loading the program because the struct_ops map has pointers directly into the BTF data.
We're already storing the BTF type_id in struct bpf_struct_ops. Because type_id is stable, we can therefore just update the places where we were looking at those pointers to instead do the lookups we need from the type_id.
Fixes: 590a00888250 ("bpf: libbpf: Add STRUCT_OPS support") Signed-off-by: David Vernet void@manifault.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/bpf/20240724171459.281234-1-void@manifault.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/lib/bpf/libbpf.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index a3be6f8fac09e..e553538874393 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -496,8 +496,6 @@ struct bpf_program { };
struct bpf_struct_ops { - const char *tname; - const struct btf_type *type; struct bpf_program **progs; __u32 *kern_func_off; /* e.g. struct tcp_congestion_ops in bpf_prog's btf format */ @@ -1083,11 +1081,14 @@ static int bpf_object_adjust_struct_ops_autoload(struct bpf_object *obj) continue;
for (j = 0; j < obj->nr_maps; ++j) { + const struct btf_type *type; + map = &obj->maps[j]; if (!bpf_map__is_struct_ops(map)) continue;
- vlen = btf_vlen(map->st_ops->type); + type = btf__type_by_id(obj->btf, map->st_ops->type_id); + vlen = btf_vlen(type); for (k = 0; k < vlen; ++k) { slot_prog = map->st_ops->progs[k]; if (prog != slot_prog) @@ -1121,8 +1122,8 @@ static int bpf_map__init_kern_struct_ops(struct bpf_map *map) int err;
st_ops = map->st_ops; - type = st_ops->type; - tname = st_ops->tname; + type = btf__type_by_id(btf, st_ops->type_id); + tname = btf__name_by_offset(btf, type->name_off); err = find_struct_ops_kern_types(obj, tname, &mod_btf, &kern_type, &kern_type_id, &kern_vtype, &kern_vtype_id, @@ -1423,8 +1424,6 @@ static int init_struct_ops_maps(struct bpf_object *obj, const char *sec_name, memcpy(st_ops->data, data->d_buf + vsi->offset, type->size); - st_ops->tname = tname; - st_ops->type = type; st_ops->type_id = type_id;
pr_debug("struct_ops init: struct %s(type_id=%u) %s found at offset %u\n", @@ -8445,11 +8444,13 @@ static int bpf_object__resolve_externs(struct bpf_object *obj,
static void bpf_map_prepare_vdata(const struct bpf_map *map) { + const struct btf_type *type; struct bpf_struct_ops *st_ops; __u32 i;
st_ops = map->st_ops; - for (i = 0; i < btf_vlen(st_ops->type); i++) { + type = btf__type_by_id(map->obj->btf, st_ops->type_id); + for (i = 0; i < btf_vlen(type); i++) { struct bpf_program *prog = st_ops->progs[i]; void *kern_data; int prog_fd; @@ -9712,6 +9713,7 @@ static struct bpf_map *find_struct_ops_map_by_offset(struct bpf_object *obj, static int bpf_object__collect_st_ops_relos(struct bpf_object *obj, Elf64_Shdr *shdr, Elf_Data *data) { + const struct btf_type *type; const struct btf_member *member; struct bpf_struct_ops *st_ops; struct bpf_program *prog; @@ -9771,13 +9773,14 @@ static int bpf_object__collect_st_ops_relos(struct bpf_object *obj, } insn_idx = sym->st_value / BPF_INSN_SZ;
- member = find_member_by_offset(st_ops->type, moff * 8); + type = btf__type_by_id(btf, st_ops->type_id); + member = find_member_by_offset(type, moff * 8); if (!member) { pr_warn("struct_ops reloc %s: cannot find member at moff %u\n", map->name, moff); return -EINVAL; } - member_idx = member - btf_members(st_ops->type); + member_idx = member - btf_members(type); name = btf__name_by_offset(btf, member->name_off);
if (!resolve_func_ptr(btf, member->type, NULL)) {