From e9d9450497f77ee40c7d895bf1b5b134b9347d5f Mon Sep 17 00:00:00 2001 From: Chema Gonzalez Date: Fri, 30 May 2014 10:15:12 -0700 Subject: [PATCH] net: filter: fix length calculation in BPF testsuite The current probe_filter_length() (the function that calculates the length of a test BPF filter) behavior is to declare the end of the filter as soon as it finds {0, *, *, 0}. This is actually a valid insn ("ld #0"), so any filter with includes "BPF_STMT(BPF_LD | BPF_IMM, 0)" fails (its length is cut short). We are changing probe_filter_length() so as to start from the end, and declare the end of the filter as the first instruction which is not {0, *, *, 0}. This solution produces a simpler patch than the alternative of using an explicit end-of-filter mark. It is technically incorrect if your filter ends up with "ld #0", but that should not happen anyway. We also add a new test (LD_IMM_0) that includes ld #0 (does not work without this patch). Signed-off-by: Chema Gonzalez Acked-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- lib/test_bpf.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/lib/test_bpf.c b/lib/test_bpf.c index f8d2b2a13131..ea60ad8d5242 100644 --- a/lib/test_bpf.c +++ b/lib/test_bpf.c @@ -157,6 +157,18 @@ static struct bpf_test tests[] = { { }, { { 0, 0x800000ff }, { 1, 0x800000ff } }, }, + { + "LD_IMM_0", + .u.insns = { + BPF_STMT(BPF_LD | BPF_IMM, 0), /* ld #0 */ + BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 0, 1, 0), + BPF_STMT(BPF_RET | BPF_K, 0), + BPF_STMT(BPF_RET | BPF_K, 1), + }, + CLASSIC, + { }, + { { 1, 1 } }, + }, { "LD_IND", .u.insns = { @@ -1734,12 +1746,11 @@ static int probe_filter_length(struct sock_filter *fp) { int len = 0; - while (fp->code != 0 || fp->k != 0) { - fp++; - len++; - } + for (len = MAX_INSNS - 1; len > 0; --len) + if (fp[len].code != 0 || fp[len].k != 0) + break; - return len; + return len + 1; } static struct sk_filter *generate_filter(int which, int *err) -- 2.20.1