[ upstream commit 7891a87efc7116590eaba57acc3c422487802c6f ]
The following snippet was throwing an 'unknown opcode cc' warning in BPF interpreter:
0: (18) r0 = 0x0 2: (7b) *(u64 *)(r10 -16) = r0 3: (cc) (u32) r0 s>>= (u32) r0 4: (95) exit
Although a number of JITs do support BPF_ALU | BPF_ARSH | BPF_{K,X} generation, not all of them do and interpreter does neither. We can leave existing ones and implement it later in bpf-next for the remaining ones, but reject this properly in verifier for the time being.
Fixes: 17a5267067f3 ("bpf: verifier (add verifier core)") Reported-by: syzbot+93c4904c5c70348a6890@syzkaller.appspotmail.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Alexei Starovoitov ast@kernel.org --- kernel/bpf/verifier.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index a626797..32af151 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1165,6 +1165,11 @@ static int check_alu_op(struct verifier_env *env, struct bpf_insn *insn) return -EINVAL; }
+ if (opcode == BPF_ARSH && BPF_CLASS(insn->code) != BPF_ALU64) { + verbose("BPF_ARSH not supported for 32 bit ALU\n"); + return -EINVAL; + } + if ((opcode == BPF_LSH || opcode == BPF_RSH || opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) { int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32;