From 0fd4759c5515b7f2297d7fee5c45e5d9dd733001 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Sat, 21 Oct 2017 02:34:22 +0200 Subject: [PATCH] bpf: fix pattern matches for direct packet access Alexander had a test program with direct packet access, where the access test was in the form of data + X > data_end. In an unrelated change to the program LLVM decided to swap the branches and emitted code for the test in form of data + X <= data_end. We hadn't seen these being generated previously, thus verifier would reject the program. Therefore, fix up the verifier to detect all test cases, so we don't run into such issues in the future. Fixes: b4e432f1000a ("bpf: enable BPF_J{LT, LE, SLT, SLE} opcodes in verifier") Reported-by: Alexander Alemayhu Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Acked-by: John Fastabend Signed-off-by: David S. Miller --- kernel/bpf/verifier.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 49cb5ad14746..c48ca2a34b5e 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2874,18 +2874,42 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT && dst_reg->type == PTR_TO_PACKET && regs[insn->src_reg].type == PTR_TO_PACKET_END) { + /* pkt_data' > pkt_end */ find_good_pkt_pointers(this_branch, dst_reg, false); + } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT && + dst_reg->type == PTR_TO_PACKET_END && + regs[insn->src_reg].type == PTR_TO_PACKET) { + /* pkt_end > pkt_data' */ + find_good_pkt_pointers(other_branch, ®s[insn->src_reg], true); } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JLT && dst_reg->type == PTR_TO_PACKET && regs[insn->src_reg].type == PTR_TO_PACKET_END) { + /* pkt_data' < pkt_end */ find_good_pkt_pointers(other_branch, dst_reg, true); + } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JLT && + dst_reg->type == PTR_TO_PACKET_END && + regs[insn->src_reg].type == PTR_TO_PACKET) { + /* pkt_end < pkt_data' */ + find_good_pkt_pointers(this_branch, ®s[insn->src_reg], false); + } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGE && + dst_reg->type == PTR_TO_PACKET && + regs[insn->src_reg].type == PTR_TO_PACKET_END) { + /* pkt_data' >= pkt_end */ + find_good_pkt_pointers(this_branch, dst_reg, true); } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGE && dst_reg->type == PTR_TO_PACKET_END && regs[insn->src_reg].type == PTR_TO_PACKET) { + /* pkt_end >= pkt_data' */ find_good_pkt_pointers(other_branch, ®s[insn->src_reg], false); + } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JLE && + dst_reg->type == PTR_TO_PACKET && + regs[insn->src_reg].type == PTR_TO_PACKET_END) { + /* pkt_data' <= pkt_end */ + find_good_pkt_pointers(other_branch, dst_reg, false); } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JLE && dst_reg->type == PTR_TO_PACKET_END && regs[insn->src_reg].type == PTR_TO_PACKET) { + /* pkt_end <= pkt_data' */ find_good_pkt_pointers(this_branch, ®s[insn->src_reg], true); } else if (is_pointer_value(env, insn->dst_reg)) { verbose("R%d pointer comparison prohibited\n", insn->dst_reg); -- 2.20.1