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bpf: fix out of bounds access in verifier log

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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>
This commit is contained in:
Alexei Starovoitov 2015-09-08 13:40:01 -07:00 committed by David S. Miller
parent 6b9ea5a64e
commit 687f07156b
1 changed files with 2 additions and 2 deletions
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4
kernel/bpf/verifier.c
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@ -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] = ">",