From: Eduard Zingerman <eddyz87@gmail.com> stable inclusion from stable-v6.6.54 commit 2288b54b96dcb55bedebcef3572bb8821fc5e708 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYQR6 CVE: CVE-2024-49850 [ Upstream commit 3d2786d65aaa954ebd3fcc033ada433e10da21c4 ] In case of malformed relocation record of kind BPF_CORE_TYPE_ID_LOCAL referencing a non-existing BTF type, function bpf_core_calc_relo_insn would cause a null pointer deference. Fix this by adding a proper check upper in call stack, as malformed relocation records could be passed from user space. Simplest reproducer is a program: r0 = 0 exit With a single relocation record: .insn_off = 0, /* patch first instruction */ .type_id = 100500, /* this type id does not exist */ .access_str_off = 6, /* offset of string "0" */ .kind = BPF_CORE_TYPE_ID_LOCAL, See the link for original reproducer or next commit for a test case. Fixes: 74753e1462e7 ("libbpf: Replace btf__type_by_id() with btf_type_by_id().") Reported-by: Liu RuiTong <cnitlrt@gmail.com> Closes: https://lore.kernel.org/bpf/CAK55_s6do7C+DVwbwY_7nKfUz0YLDoiA1v6X3Y9+p0sWzip... Acked-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20240822080124.2995724-2-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Xiaomeng Zhang <zhangxiaomeng13@huawei.com> --- kernel/bpf/btf.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 7ac62793a753..01303bb8ee29 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -8419,6 +8419,7 @@ int bpf_core_apply(struct bpf_core_ctx *ctx, const struct bpf_core_relo *relo, struct bpf_core_cand_list cands = {}; struct bpf_core_relo_res targ_res; struct bpf_core_spec *specs; + const struct btf_type *type; int err; /* ~4k of temp memory necessary to convert LLVM spec like "0:1:0:5" @@ -8428,6 +8429,13 @@ int bpf_core_apply(struct bpf_core_ctx *ctx, const struct bpf_core_relo *relo, if (!specs) return -ENOMEM; + type = btf_type_by_id(ctx->btf, relo->type_id); + if (!type) { + bpf_log(ctx->log, "relo #%u: bad type id %u\n", + relo_idx, relo->type_id); + return -EINVAL; + } + if (need_cands) { struct bpf_cand_cache *cc; int i; -- 2.34.1