lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Mon,  1 Apr 2019 13:57:33 -0700
From:   Stanislav Fomichev <>
Cc:,,,,,, Stanislav Fomichev <>
Subject: [PATCH bpf 4/5] flow_dissector: allow access only to a subset of
 __sk_buff fields

Use whitelist instead of a blacklist and allow only a small set of
fields that might be relevant in the context of flow dissector:
  * data
  * data_end
  * flow_keys

This is required for the eth_get_headlen case where we have only a
chunk of data to dissect (i.e. trying to read the other skb fields
doesn't make sense).

Note, that it is a breaking API change! However, we've provided
flow_keys->n_proto as a substitute for skb->protocol; and there is
no need to manually handle skb->vlan_present. So even if we
break somebody, the migration is trivial. Unfortunately, we can't
support eth_get_headlen use-case without those breaking changes.

Signed-off-by: Stanislav Fomichev <>
 net/core/filter.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 647c63a7b25b..fc92ebc4e200 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -6613,14 +6613,8 @@ static bool flow_dissector_is_valid_access(int off, int size,
 					   const struct bpf_prog *prog,
 					   struct bpf_insn_access_aux *info)
-	if (type == BPF_WRITE) {
-		switch (off) {
-		case bpf_ctx_range_till(struct __sk_buff, cb[0], cb[4]):
-			break;
-		default:
-			return false;
-		}
-	}
+	if (type == BPF_WRITE)
+		return false;
 	switch (off) {
 	case bpf_ctx_range(struct __sk_buff, data):
@@ -6632,11 +6626,7 @@ static bool flow_dissector_is_valid_access(int off, int size,
 	case bpf_ctx_range_ptr(struct __sk_buff, flow_keys):
 		info->reg_type = PTR_TO_FLOW_KEYS;
-	case bpf_ctx_range(struct __sk_buff, tc_classid):
-	case bpf_ctx_range(struct __sk_buff, data_meta):
-	case bpf_ctx_range_till(struct __sk_buff, family, local_port):
-	case bpf_ctx_range(struct __sk_buff, tstamp):
-	case bpf_ctx_range(struct __sk_buff, wire_len):
+	default:
 		return false;

Powered by blists - more mailing lists