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authorJosef Bacik <jbacik@fb.com>2017-11-07 15:28:42 -0500
committerDavid S. Miller <davem@davemloft.net>2017-11-11 12:18:05 +0900
commitdd0bb688eaa241b5655d396d45366cba9225aed9 (patch)
tree80e320112959e90d474fd20e644b8377217dad0b /kernel/bpf
parent54985120a1c461b74f9510e5d730971f2a2383b1 (diff)
downloadlinux-dd0bb688eaa241b5655d396d45366cba9225aed9.tar.bz2
bpf: add a bpf_override_function helper
Error injection is sloppy and very ad-hoc. BPF could fill this niche perfectly with it's kprobe functionality. We could make sure errors are only triggered in specific call chains that we care about with very specific situations. Accomplish this with the bpf_override_funciton helper. This will modify the probe'd callers return value to the specified value and set the PC to an override function that simply returns, bypassing the originally probed function. This gives us a nice clean way to implement systematic error injection for all of our code paths. Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Josef Bacik <jbacik@fb.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/core.c3
-rw-r--r--kernel/bpf/verifier.c2
2 files changed, 5 insertions, 0 deletions
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 8a6c37762330..271daad31f37 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1326,6 +1326,9 @@ EVAL4(PROG_NAME_LIST, 416, 448, 480, 512)
bool bpf_prog_array_compatible(struct bpf_array *array,
const struct bpf_prog *fp)
{
+ if (fp->kprobe_override)
+ return false;
+
if (!array->owner_prog_type) {
/* There's no owner yet where we could check for
* compatibility.
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 4a942e2e753d..bc464b8ec91e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4357,6 +4357,8 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
prog->dst_needed = 1;
if (insn->imm == BPF_FUNC_get_prandom_u32)
bpf_user_rnd_init_once();
+ if (insn->imm == BPF_FUNC_override_return)
+ prog->kprobe_override = 1;
if (insn->imm == BPF_FUNC_tail_call) {
/* If we tail call into other programs, we
* cannot make any assumptions since they can