Commit 687f0715 authored Sep 08, 2015 by Alexei Starovoitov Committed by David S. Miller Sep 09, 2015

bpf: fix out of bounds access in verifier log



when the verifier log is enabled the print_bpf_insn() is doing
bpf_alu_string[BPF_OP(insn->code) >> 4]
and
bpf_jmp_string[BPF_OP(insn->code) >> 4]
where BPF_OP is a 4-bit instruction opcode.
Malformed insns can cause out of bounds access.
Fix it by sizing arrays appropriately.

The bug was found by clang address sanitizer with libfuzzer.

Reported-by: Yonghong Song <yhs@plumgrid.com>
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 6b9ea5a6

kernel/bpf/verifier.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -283,7 +283,7 @@ static const char *const bpf_class_string[] = {
		[BPF_ALU64] = "alu64",
		};

		static const char *const bpf_alu_string[] = {
		static const char *const bpf_alu_string[16] = {
		[BPF_ADD >> 4] = "+=",
		[BPF_SUB >> 4] = "-=",
		[BPF_MUL >> 4] = "*=",
		@@ -307,7 +307,7 @@ static const char *const bpf_ldst_string[] = {
		[BPF_DW >> 3] = "u64",
		};

		static const char *const bpf_jmp_string[] = {
		static const char *const bpf_jmp_string[16] = {
		[BPF_JA >> 4] = "jmp",
		[BPF_JEQ >> 4] = "==",
		[BPF_JGT >> 4] = ">",

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