Since "92acdc58ab11 bpf, net: Rework cookie generator as per-cpu one"
socket cookies are not guaranteed to be non-decreasing. The
bpf_get_socket_cookie helper descriptions are currently specifying that
cookies are non-decreasing but we don't want users to rely on that.
Reported-by: Daniel Borkmann <[email protected]>
Signed-off-by: Florent Revest <[email protected]>
Acked-by: KP Singh <[email protected]>
---
include/uapi/linux/bpf.h | 8 ++++----
tools/include/uapi/linux/bpf.h | 8 ++++----
2 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c001766adcbc..0b735c2729b2 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1656,22 +1656,22 @@ union bpf_attr {
* networking traffic statistics as it provides a global socket
* identifier that can be assumed unique.
* Return
- * A 8-byte long non-decreasing number on success, or 0 if the
- * socket field is missing inside *skb*.
+ * A 8-byte long unique number on success, or 0 if the socket
+ * field is missing inside *skb*.
*
* u64 bpf_get_socket_cookie(struct bpf_sock_addr *ctx)
* Description
* Equivalent to bpf_get_socket_cookie() helper that accepts
* *skb*, but gets socket from **struct bpf_sock_addr** context.
* Return
- * A 8-byte long non-decreasing number.
+ * A 8-byte long unique number.
*
* u64 bpf_get_socket_cookie(struct bpf_sock_ops *ctx)
* Description
* Equivalent to **bpf_get_socket_cookie**\ () helper that accepts
* *skb*, but gets socket from **struct bpf_sock_ops** context.
* Return
- * A 8-byte long non-decreasing number.
+ * A 8-byte long unique number.
*
* u32 bpf_get_socket_uid(struct sk_buff *skb)
* Return
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index c001766adcbc..0b735c2729b2 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1656,22 +1656,22 @@ union bpf_attr {
* networking traffic statistics as it provides a global socket
* identifier that can be assumed unique.
* Return
- * A 8-byte long non-decreasing number on success, or 0 if the
- * socket field is missing inside *skb*.
+ * A 8-byte long unique number on success, or 0 if the socket
+ * field is missing inside *skb*.
*
* u64 bpf_get_socket_cookie(struct bpf_sock_addr *ctx)
* Description
* Equivalent to bpf_get_socket_cookie() helper that accepts
* *skb*, but gets socket from **struct bpf_sock_addr** context.
* Return
- * A 8-byte long non-decreasing number.
+ * A 8-byte long unique number.
*
* u64 bpf_get_socket_cookie(struct bpf_sock_ops *ctx)
* Description
* Equivalent to **bpf_get_socket_cookie**\ () helper that accepts
* *skb*, but gets socket from **struct bpf_sock_ops** context.
* Return
- * A 8-byte long non-decreasing number.
+ * A 8-byte long unique number.
*
* u32 bpf_get_socket_uid(struct sk_buff *skb)
* Return
--
2.30.0.478.g8a0d178c01-goog
When migrating from the bpf.h's to the vmlinux.h's definition of struct
bps_sock, an interesting LLVM behavior happened. LLVM started producing
two fetches of ctx->sk in the sockops program this means that the
verifier could not keep track of the NULL-check on ctx->sk. Therefore,
we need to extract ctx->sk in a variable before checking and
dereferencing it.
Acked-by: KP Singh <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>
Signed-off-by: Florent Revest <[email protected]>
---
.../testing/selftests/bpf/progs/socket_cookie_prog.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/socket_cookie_prog.c b/tools/testing/selftests/bpf/progs/socket_cookie_prog.c
index 81e84be6f86d..fbd5eaf39720 100644
--- a/tools/testing/selftests/bpf/progs/socket_cookie_prog.c
+++ b/tools/testing/selftests/bpf/progs/socket_cookie_prog.c
@@ -1,12 +1,13 @@
// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2018 Facebook
-#include <linux/bpf.h>
-#include <sys/socket.h>
+#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
+#define AF_INET6 10
+
struct socket_cookie {
__u64 cookie_key;
__u32 cookie_value;
@@ -41,7 +42,7 @@ int set_cookie(struct bpf_sock_addr *ctx)
SEC("sockops")
int update_cookie(struct bpf_sock_ops *ctx)
{
- struct bpf_sock *sk;
+ struct bpf_sock *sk = ctx->sk;
struct socket_cookie *p;
if (ctx->family != AF_INET6)
@@ -50,10 +51,10 @@ int update_cookie(struct bpf_sock_ops *ctx)
if (ctx->op != BPF_SOCK_OPS_TCP_CONNECT_CB)
return 1;
- if (!ctx->sk)
+ if (!sk)
return 1;
- p = bpf_sk_storage_get(&socket_cookies, ctx->sk, 0, 0);
+ p = bpf_sk_storage_get(&socket_cookies, sk, 0, 0);
if (!p)
return 1;
--
2.30.0.478.g8a0d178c01-goog
This builds up on the existing socket cookie test which checks whether
the bpf_get_socket_cookie helpers provide the same value in
cgroup/connect6 and sockops programs for a socket created by the
userspace part of the test.
Instead of having an update_cookie sockops program tag a socket local
storage with 0xFF, this uses both an update_cookie_sockops program and
an update_cookie_tracing program which succesively tag the socket with
0x0F and then 0xF0.
Signed-off-by: Florent Revest <[email protected]>
Acked-by: KP Singh <[email protected]>
---
.../selftests/bpf/prog_tests/socket_cookie.c | 11 ++++--
.../selftests/bpf/progs/socket_cookie_prog.c | 36 +++++++++++++++++--
2 files changed, 41 insertions(+), 6 deletions(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/socket_cookie.c b/tools/testing/selftests/bpf/prog_tests/socket_cookie.c
index e12a31d3752c..232db28dde18 100644
--- a/tools/testing/selftests/bpf/prog_tests/socket_cookie.c
+++ b/tools/testing/selftests/bpf/prog_tests/socket_cookie.c
@@ -35,9 +35,14 @@ void test_socket_cookie(void)
if (!ASSERT_OK_PTR(skel->links.set_cookie, "prog_attach"))
goto close_cgroup_fd;
- skel->links.update_cookie = bpf_program__attach_cgroup(
- skel->progs.update_cookie, cgroup_fd);
- if (!ASSERT_OK_PTR(skel->links.update_cookie, "prog_attach"))
+ skel->links.update_cookie_sockops = bpf_program__attach_cgroup(
+ skel->progs.update_cookie_sockops, cgroup_fd);
+ if (!ASSERT_OK_PTR(skel->links.update_cookie_sockops, "prog_attach"))
+ goto close_cgroup_fd;
+
+ skel->links.update_cookie_tracing = bpf_program__attach(
+ skel->progs.update_cookie_tracing);
+ if (!ASSERT_OK_PTR(skel->links.update_cookie_tracing, "prog_attach"))
goto close_cgroup_fd;
server_fd = start_server(AF_INET6, SOCK_STREAM, "::1", 0, 0);
diff --git a/tools/testing/selftests/bpf/progs/socket_cookie_prog.c b/tools/testing/selftests/bpf/progs/socket_cookie_prog.c
index fbd5eaf39720..35630a5aaf5f 100644
--- a/tools/testing/selftests/bpf/progs/socket_cookie_prog.c
+++ b/tools/testing/selftests/bpf/progs/socket_cookie_prog.c
@@ -5,6 +5,7 @@
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
+#include <bpf/bpf_tracing.h>
#define AF_INET6 10
@@ -20,6 +21,14 @@ struct {
__type(value, struct socket_cookie);
} socket_cookies SEC(".maps");
+/*
+ * These three programs get executed in a row on connect() syscalls. The
+ * userspace side of the test creates a client socket, issues a connect() on it
+ * and then checks that the local storage associated with this socket has:
+ * cookie_value == local_port << 8 | 0xFF
+ * The different parts of this cookie_value are appended by those hooks if they
+ * all agree on the output of bpf_get_socket_cookie().
+ */
SEC("cgroup/connect6")
int set_cookie(struct bpf_sock_addr *ctx)
{
@@ -33,14 +42,14 @@ int set_cookie(struct bpf_sock_addr *ctx)
if (!p)
return 1;
- p->cookie_value = 0xFF;
+ p->cookie_value = 0xF;
p->cookie_key = bpf_get_socket_cookie(ctx);
return 1;
}
SEC("sockops")
-int update_cookie(struct bpf_sock_ops *ctx)
+int update_cookie_sockops(struct bpf_sock_ops *ctx)
{
struct bpf_sock *sk = ctx->sk;
struct socket_cookie *p;
@@ -61,9 +70,30 @@ int update_cookie(struct bpf_sock_ops *ctx)
if (p->cookie_key != bpf_get_socket_cookie(ctx))
return 1;
- p->cookie_value = (ctx->local_port << 8) | p->cookie_value;
+ p->cookie_value |= (ctx->local_port << 8);
return 1;
}
+SEC("fexit/inet_stream_connect")
+int BPF_PROG(update_cookie_tracing, struct socket *sock,
+ struct sockaddr *uaddr, int addr_len, int flags)
+{
+ struct socket_cookie *p;
+
+ if (uaddr->sa_family != AF_INET6)
+ return 0;
+
+ p = bpf_sk_storage_get(&socket_cookies, sock->sk, 0, 0);
+ if (!p)
+ return 0;
+
+ if (p->cookie_key != bpf_get_socket_cookie(sock->sk))
+ return 0;
+
+ p->cookie_value |= 0xF0;
+
+ return 0;
+}
+
char _license[] SEC("license") = "GPL";
--
2.30.0.478.g8a0d178c01-goog
Hello:
This series was applied to bpf/bpf-next.git (refs/heads/master):
On Wed, 10 Feb 2021 12:14:02 +0100 you wrote:
> Since "92acdc58ab11 bpf, net: Rework cookie generator as per-cpu one"
> socket cookies are not guaranteed to be non-decreasing. The
> bpf_get_socket_cookie helper descriptions are currently specifying that
> cookies are non-decreasing but we don't want users to rely on that.
>
> Reported-by: Daniel Borkmann <[email protected]>
> Signed-off-by: Florent Revest <[email protected]>
> Acked-by: KP Singh <[email protected]>
>
> [...]
Here is the summary with links:
- [bpf-next,v7,1/5] bpf: Be less specific about socket cookies guarantees
https://git.kernel.org/bpf/bpf-next/c/07881ccbf40c
- [bpf-next,v7,2/5] bpf: Expose bpf_get_socket_cookie to tracing programs
https://git.kernel.org/bpf/bpf-next/c/c5dbb89fc2ac
- [bpf-next,v7,3/5] selftests/bpf: Integrate the socket_cookie test to test_progs
https://git.kernel.org/bpf/bpf-next/c/61f8c9c8f3c8
- [bpf-next,v7,4/5] selftests/bpf: Use vmlinux.h in socket_cookie_prog.c
https://git.kernel.org/bpf/bpf-next/c/6cd4dcc3fb81
- [bpf-next,v7,5/5] selftests/bpf: Add a selftest for the tracing bpf_get_socket_cookie
https://git.kernel.org/bpf/bpf-next/c/6fdd671baaf5
You are awesome, thank you!
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