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([38.34.87.7]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7143424e145sm231448b3a.55.2024.08.21.17.18.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Aug 2024 17:18:50 -0700 (PDT) From: Eduard Zingerman To: bpf@vger.kernel.org, ast@kernel.org Cc: andrii@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, kernel-team@fb.com, yonghong.song@linux.dev, cnitlrt@gmail.com, Eduard Zingerman Subject: [PATCH bpf-next v2 1/2] bpf: correctly handle malformed BPF_CORE_TYPE_ID_LOCAL relos Date: Wed, 21 Aug 2024 17:18:36 -0700 Message-ID: <20240822001837.2715909-2-eddyz87@gmail.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240822001837.2715909-1-eddyz87@gmail.com> References: <20240822001837.2715909-1-eddyz87@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net 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 Closes: https://lore.kernel.org/bpf/CAK55_s6do7C+DVwbwY_7nKfUz0YLDoiA1v6X3Y9+p0sWzipFSA@mail.gmail.com/ Signed-off-by: Eduard Zingerman Acked-by: Andrii Nakryiko --- kernel/bpf/btf.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index b12db397303e..e38e770a6945 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -8888,6 +8888,7 @@ 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" @@ -8897,6 +8898,13 @@ 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;