From bddeb44981c1f5dd699ff45cce6ce31e59c0300c Mon Sep 17 00:00:00 2001 From: Edward Cree Date: Fri, 16 Nov 2018 12:00:07 +0000 Subject: [PATCH] bpf: fix off-by-one error in adjust_subprog_starts commit afd594240806acc138cf696c09f2f4829d55d02f upstream. When patching in a new sequence for the first insn of a subprog, the start of that subprog does not change (it's the first insn of the sequence), so adjust_subprog_starts should check start <= off (rather than < off). Also added a test to test_verifier.c (it's essentially the syz reproducer). Fixes: cc8b0b92a169 ("bpf: introduce function calls (function boundaries)") Reported-by: syzbot+4fc427c7af994b0948be@syzkaller.appspotmail.com Signed-off-by: Edward Cree Acked-by: Yonghong Song Signed-off-by: Alexei Starovoitov Signed-off-by: Greg Kroah-Hartman --- kernel/bpf/verifier.c | 2 +- tools/testing/selftests/bpf/test_verifier.c | 19 +++++++++++++++++++ 2 files changed, 20 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 5780876..56acfbb 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5283,7 +5283,7 @@ static void adjust_subprog_starts(struct bpf_verifier_env *env, u32 off, u32 len return; /* NOTE: fake 'exit' subprog should be updated as well. */ for (i = 0; i <= env->subprog_cnt; i++) { - if (env->subprog_info[i].start < off) + if (env->subprog_info[i].start <= off) continue; env->subprog_info[i].start += len - 1; } diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index 67c412d..2bde9ee 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -12511,6 +12511,25 @@ static struct bpf_test tests[] = { .prog_type = BPF_PROG_TYPE_SCHED_CLS, .result = ACCEPT, }, + { + "calls: ctx read at start of subprog", + .insns = { + BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, 5), + BPF_JMP_REG(BPF_JSGT, BPF_REG_0, BPF_REG_0, 0), + BPF_MOV64_REG(BPF_REG_1, BPF_REG_6), + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, 2), + BPF_MOV64_REG(BPF_REG_1, BPF_REG_0), + BPF_EXIT_INSN(), + BPF_LDX_MEM(BPF_B, BPF_REG_9, BPF_REG_1, 0), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .prog_type = BPF_PROG_TYPE_SOCKET_FILTER, + .errstr_unpriv = "function calls to other bpf functions are allowed for root only", + .result_unpriv = REJECT, + .result = ACCEPT, + }, }; static int probe_filter_length(const struct bpf_insn *fp) -- 2.7.4