6.1-stable review patch. If anyone has any objections, please let me know.
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From: Eduard Zingerman eddyz87@gmail.com
[ 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 --- kernel/bpf/btf.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 95a050446f271..8c684a0e1c4bc 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -7973,6 +7973,7 @@ 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" @@ -7982,6 +7983,13 @@ 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;