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Commit 687f0715 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
Browse files

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: default avatarYonghong Song <yhs@plumgrid.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid 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]  = ">",