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authorDaniel Borkmann <daniel@iogearbox.net>2017-12-14 23:07:25 +0300
committerAlexei Starovoitov <ast@kernel.org>2017-12-15 20:19:35 +0300
commit04514d13222f2c4c91adf0ecb21004cec3388795 (patch)
tree18f3909ec2918ce8b46cac6ed9d76013dc603022 /kernel
parent87338c8e2cbb317b5f757e6172f94e2e3799cd20 (diff)
downloadlinux-04514d13222f2c4c91adf0ecb21004cec3388795.tar.xz
bpf: guarantee r1 to be ctx in case of bpf_helper_changes_pkt_data
Some JITs don't cache skb context on stack in prologue, so when LD_ABS/IND is used and helper calls yield bpf_helper_changes_pkt_data() as true, then they temporarily save/restore skb pointer. However, the assumption that skb always has to be in r1 is a bit of a gamble. Right now it turned out to be true for all helpers listed in bpf_helper_changes_pkt_data(), but lets enforce that from verifier side, so that we make this a guarantee and bail out if the func proto is misconfigured in future helpers. In case of BPF helper calls from cBPF, bpf_helper_changes_pkt_data() is completely unrelevant here (since cBPF is context read-only) and therefore always false. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/verifier.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d4593571c404..e39b01317b6f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1674,7 +1674,13 @@ static int check_call(struct bpf_verifier_env *env, int func_id, int insn_idx)
return -EINVAL;
}
+ /* With LD_ABS/IND some JITs save/restore skb from r1. */
changes_data = bpf_helper_changes_pkt_data(fn->func);
+ if (changes_data && fn->arg1_type != ARG_PTR_TO_CTX) {
+ verbose(env, "kernel subsystem misconfigured func %s#%d: r1 != ctx\n",
+ func_id_name(func_id), func_id);
+ return -EINVAL;
+ }
memset(&meta, 0, sizeof(meta));
meta.pkt_access = fn->pkt_access;