* [PATCH bpf-next v4 1/2] bpf, sockmap: disallow update and delete from tc, xdp, socket_filter and flow_dissector
2026-06-30 14:54 [PATCH bpf-next v4 0/2] bpf, sockmap: disallow sockmap mutation from tc, xdp, socket_filter and flow_dissector Sechang Lim
@ 2026-06-30 14:54 ` Sechang Lim
2026-07-01 0:07 ` John Fastabend
2026-06-30 14:54 ` [PATCH bpf-next v4 2/2] selftests/bpf: drop tc/xdp/flow_dissector/socket_filter sockmap mutation tests Sechang Lim
1 sibling, 1 reply; 5+ messages in thread
From: Sechang Lim @ 2026-06-30 14:54 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
Eduard Zingerman, Kumar Kartikeya Dwivedi, John Fastabend,
David S. Miller, Jakub Kicinski, Jesper Dangaard Brouer,
Shuah Khan
Cc: Martin KaFai Lau, Song Liu, Yonghong Song, Jiri Olsa,
Emil Tsalapatis, Stanislav Fomichev, Jiayuan Chen, Varun R Mallya,
Ihor Solodrai, bpf, netdev, linux-kernel, linux-kselftest
sock_map_update_common() and __sock_map_delete() hold stab->lock and call
sock_map_unref() -> sock_map_del_link(), which takes sk_callback_lock for
write. That gives the order stab->lock -> sk_callback_lock.
The reverse order comes from the SK_SKB stream parser.
sk_psock_strp_data_ready() holds sk_callback_lock for read, and after the
verdict tcp_bpf_strp_read_sock() acks the consumed data inline via
__tcp_cleanup_rbuf(). The ACK goes out egress, where a sched_cls program
deletes from the sockmap and takes stab->lock:
WARNING: possible circular locking dependency detected
------------------------------------------------------
syz.9.8824 is trying to acquire lock:
(&stab->lock){+.-.}-{3:3}, at: __sock_map_delete net/core/sock_map.c:421
but task is already holding lock:
(clock-AF_INET){++.-}-{3:3}, at: sk_psock_strp_data_ready net/core/skmsg.c:1173
-> #1 (clock-AF_INET){++.-}-{3:3}:
_raw_write_lock_bh
sock_map_del_link net/core/sock_map.c:167
sock_map_unref net/core/sock_map.c:184
sock_map_update_common net/core/sock_map.c:509
sock_map_update_elem_sys net/core/sock_map.c:588
map_update_elem kernel/bpf/syscall.c:1805
-> #0 (&stab->lock){+.-.}-{3:3}:
_raw_spin_lock_bh
__sock_map_delete net/core/sock_map.c:421
sock_map_delete_elem net/core/sock_map.c:452
bpf_prog_06044d24140080b6
tcx_run net/core/dev.c:4451
sch_handle_egress net/core/dev.c:4541
__dev_queue_xmit net/core/dev.c:4808
...
tcp_bpf_strp_read_sock net/ipv4/tcp_bpf.c:701
strp_data_ready net/strparser/strparser.c:402
sk_psock_strp_data_ready net/core/skmsg.c:1174
tcp_data_queue net/ipv4/tcp_input.c:5661
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
rlock(clock-AF_INET);
lock(&stab->lock);
lock(clock-AF_INET);
lock(&stab->lock);
*** DEADLOCK ***
A tc, xdp, socket_filter or flow_dissector program has no reason to
update or delete a sockmap, and redirect does not go through here. Drop
them from may_update_sockmap() so the verifier rejects it. It also
closes the matching sockhash inversion.
Suggested-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Sechang Lim <rhkrqnwk98@gmail.com>
---
kernel/bpf/verifier.c | 5 -----
1 file changed, 5 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 25aea4271cd0..83ea3b33ff67 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8488,12 +8488,7 @@ static bool may_update_sockmap(struct bpf_verifier_env *env, int func_id)
if (func_id == BPF_FUNC_map_delete_elem)
return true;
break;
- case BPF_PROG_TYPE_SOCKET_FILTER:
- case BPF_PROG_TYPE_SCHED_CLS:
- case BPF_PROG_TYPE_SCHED_ACT:
- case BPF_PROG_TYPE_XDP:
case BPF_PROG_TYPE_SK_REUSEPORT:
- case BPF_PROG_TYPE_FLOW_DISSECTOR:
case BPF_PROG_TYPE_SK_LOOKUP:
return true;
default:
--
2.43.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH bpf-next v4 2/2] selftests/bpf: drop tc/xdp/flow_dissector/socket_filter sockmap mutation tests
2026-06-30 14:54 [PATCH bpf-next v4 0/2] bpf, sockmap: disallow sockmap mutation from tc, xdp, socket_filter and flow_dissector Sechang Lim
2026-06-30 14:54 ` [PATCH bpf-next v4 1/2] bpf, sockmap: disallow update and delete " Sechang Lim
@ 2026-06-30 14:54 ` Sechang Lim
2026-07-01 0:10 ` John Fastabend
1 sibling, 1 reply; 5+ messages in thread
From: Sechang Lim @ 2026-06-30 14:54 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
Eduard Zingerman, Kumar Kartikeya Dwivedi, John Fastabend,
David S. Miller, Jakub Kicinski, Jesper Dangaard Brouer,
Shuah Khan
Cc: Martin KaFai Lau, Song Liu, Yonghong Song, Jiri Olsa,
Emil Tsalapatis, Stanislav Fomichev, Jiayuan Chen, Varun R Mallya,
Ihor Solodrai, bpf, netdev, linux-kernel, linux-kselftest
tc, xdp, socket_filter and flow_dissector programs can no longer update
or delete a sockmap. Adjust the tests:
- verifier_sockmap_mutate: the tc, xdp, socket_filter and
flow_dissector cases now expect __failure with "cannot update sockmap
in this context".
- sockmap_basic: drop "sockmap update" / "sockhash update", which load
a SEC("tc") program that copies a sock between maps.
- fexit_bpf2bpf: drop "func_sockmap_update", whose freplace program
updates a sockmap in the tc cls_redirect context.
Remove the now-unused test_sockmap_update.c and freplace_cls_redirect.c.
Signed-off-by: Sechang Lim <rhkrqnwk98@gmail.com>
---
.../selftests/bpf/prog_tests/fexit_bpf2bpf.c | 13 -----
.../selftests/bpf/prog_tests/sockmap_basic.c | 52 -------------------
.../bpf/progs/freplace_cls_redirect.c | 34 ------------
.../selftests/bpf/progs/test_sockmap_update.c | 48 -----------------
.../bpf/progs/verifier_sockmap_mutate.c | 12 ++---
5 files changed, 6 insertions(+), 153 deletions(-)
delete mode 100644 tools/testing/selftests/bpf/progs/freplace_cls_redirect.c
delete mode 100644 tools/testing/selftests/bpf/progs/test_sockmap_update.c
diff --git a/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c b/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c
index 92c20803ea76..d3a954158c33 100644
--- a/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c
+++ b/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c
@@ -336,17 +336,6 @@ static void test_fmod_ret_freplace(void)
}
-static void test_func_sockmap_update(void)
-{
- const char *prog_name[] = {
- "freplace/cls_redirect",
- };
- test_fexit_bpf2bpf_common("./freplace_cls_redirect.bpf.o",
- "./test_cls_redirect.bpf.o",
- ARRAY_SIZE(prog_name),
- prog_name, false, NULL);
-}
-
static void test_func_replace_void(void)
{
const char *prog_name[] = {
@@ -599,8 +588,6 @@ void serial_test_fexit_bpf2bpf(void)
test_func_replace();
if (test__start_subtest("func_replace_verify"))
test_func_replace_verify();
- if (test__start_subtest("func_sockmap_update"))
- test_func_sockmap_update();
if (test__start_subtest("func_replace_return_code"))
test_func_replace_return_code();
if (test__start_subtest("func_map_prog_compatibility"))
diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
index cb3229711f93..33f788e2786d 100644
--- a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
+++ b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
@@ -7,7 +7,6 @@
#include "test_progs.h"
#include "test_skmsg_load_helpers.skel.h"
-#include "test_sockmap_update.skel.h"
#include "test_sockmap_invalid_update.skel.h"
#include "test_sockmap_skb_verdict_attach.skel.h"
#include "test_sockmap_progs_query.skel.h"
@@ -235,53 +234,6 @@ static void test_skmsg_helpers_with_link(enum bpf_map_type map_type)
test_skmsg_load_helpers__destroy(skel);
}
-static void test_sockmap_update(enum bpf_map_type map_type)
-{
- int err, prog, src;
- struct test_sockmap_update *skel;
- struct bpf_map *dst_map;
- const __u32 zero = 0;
- char dummy[14] = {0};
- LIBBPF_OPTS(bpf_test_run_opts, topts,
- .data_in = dummy,
- .data_size_in = sizeof(dummy),
- .repeat = 1,
- );
- __s64 sk;
-
- sk = connected_socket_v4();
- if (!ASSERT_NEQ(sk, -1, "connected_socket_v4"))
- return;
-
- skel = test_sockmap_update__open_and_load();
- if (!ASSERT_OK_PTR(skel, "open_and_load"))
- goto close_sk;
-
- prog = bpf_program__fd(skel->progs.copy_sock_map);
- src = bpf_map__fd(skel->maps.src);
- if (map_type == BPF_MAP_TYPE_SOCKMAP)
- dst_map = skel->maps.dst_sock_map;
- else
- dst_map = skel->maps.dst_sock_hash;
-
- err = bpf_map_update_elem(src, &zero, &sk, BPF_NOEXIST);
- if (!ASSERT_OK(err, "update_elem(src)"))
- goto out;
-
- err = bpf_prog_test_run_opts(prog, &topts);
- if (!ASSERT_OK(err, "test_run"))
- goto out;
- if (!ASSERT_NEQ(topts.retval, 0, "test_run retval"))
- goto out;
-
- compare_cookies(skel->maps.src, dst_map);
-
-out:
- test_sockmap_update__destroy(skel);
-close_sk:
- close(sk);
-}
-
static void test_sockmap_invalid_update(void)
{
struct test_sockmap_invalid_update *skel;
@@ -1385,10 +1337,6 @@ void test_sockmap_basic(void)
test_skmsg_helpers(BPF_MAP_TYPE_SOCKMAP);
if (test__start_subtest("sockhash sk_msg load helpers"))
test_skmsg_helpers(BPF_MAP_TYPE_SOCKHASH);
- if (test__start_subtest("sockmap update"))
- test_sockmap_update(BPF_MAP_TYPE_SOCKMAP);
- if (test__start_subtest("sockhash update"))
- test_sockmap_update(BPF_MAP_TYPE_SOCKHASH);
if (test__start_subtest("sockmap update in unsafe context"))
test_sockmap_invalid_update();
if (test__start_subtest("sockmap copy"))
diff --git a/tools/testing/selftests/bpf/progs/freplace_cls_redirect.c b/tools/testing/selftests/bpf/progs/freplace_cls_redirect.c
deleted file mode 100644
index 7e94412d47a5..000000000000
--- a/tools/testing/selftests/bpf/progs/freplace_cls_redirect.c
+++ /dev/null
@@ -1,34 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-// Copyright (c) 2020 Facebook
-
-#include <linux/stddef.h>
-#include <linux/bpf.h>
-#include <linux/pkt_cls.h>
-#include <bpf/bpf_endian.h>
-#include <bpf/bpf_helpers.h>
-
-struct {
- __uint(type, BPF_MAP_TYPE_SOCKMAP);
- __type(key, int);
- __type(value, int);
- __uint(max_entries, 2);
-} sock_map SEC(".maps");
-
-SEC("freplace/cls_redirect")
-int freplace_cls_redirect_test(struct __sk_buff *skb)
-{
- int ret = 0;
- const int zero = 0;
- struct bpf_sock *sk;
-
- sk = bpf_map_lookup_elem(&sock_map, &zero);
- if (!sk)
- return TC_ACT_SHOT;
-
- ret = bpf_map_update_elem(&sock_map, &zero, sk, 0);
- bpf_sk_release(sk);
-
- return ret == 0 ? TC_ACT_OK : TC_ACT_SHOT;
-}
-
-char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/test_sockmap_update.c b/tools/testing/selftests/bpf/progs/test_sockmap_update.c
deleted file mode 100644
index 6d64ea536e3d..000000000000
--- a/tools/testing/selftests/bpf/progs/test_sockmap_update.c
+++ /dev/null
@@ -1,48 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-// Copyright (c) 2020 Cloudflare
-#include "vmlinux.h"
-#include <bpf/bpf_helpers.h>
-
-struct {
- __uint(type, BPF_MAP_TYPE_SOCKMAP);
- __uint(max_entries, 1);
- __type(key, __u32);
- __type(value, __u64);
-} src SEC(".maps");
-
-struct {
- __uint(type, BPF_MAP_TYPE_SOCKMAP);
- __uint(max_entries, 1);
- __type(key, __u32);
- __type(value, __u64);
-} dst_sock_map SEC(".maps");
-
-struct {
- __uint(type, BPF_MAP_TYPE_SOCKHASH);
- __uint(max_entries, 1);
- __type(key, __u32);
- __type(value, __u64);
-} dst_sock_hash SEC(".maps");
-
-SEC("tc")
-int copy_sock_map(void *ctx)
-{
- struct bpf_sock *sk;
- bool failed = false;
- __u32 key = 0;
-
- sk = bpf_map_lookup_elem(&src, &key);
- if (!sk)
- return SK_DROP;
-
- if (bpf_map_update_elem(&dst_sock_map, &key, sk, 0))
- failed = true;
-
- if (bpf_map_update_elem(&dst_sock_hash, &key, sk, 0))
- failed = true;
-
- bpf_sk_release(sk);
- return failed ? SK_DROP : SK_PASS;
-}
-
-char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/verifier_sockmap_mutate.c b/tools/testing/selftests/bpf/progs/verifier_sockmap_mutate.c
index fe4b123187b8..20332a731d4e 100644
--- a/tools/testing/selftests/bpf/progs/verifier_sockmap_mutate.c
+++ b/tools/testing/selftests/bpf/progs/verifier_sockmap_mutate.c
@@ -74,7 +74,7 @@ static __always_inline void test_sockmap_lookup_and_mutate(void)
}
SEC("action")
-__success
+__failure __msg("cannot update sockmap in this context")
int test_sched_act(struct __sk_buff *skb)
{
test_sockmap_mutate(skb->sk);
@@ -82,7 +82,7 @@ int test_sched_act(struct __sk_buff *skb)
}
SEC("classifier")
-__success
+__failure __msg("cannot update sockmap in this context")
int test_sched_cls(struct __sk_buff *skb)
{
test_sockmap_mutate(skb->sk);
@@ -90,7 +90,7 @@ int test_sched_cls(struct __sk_buff *skb)
}
SEC("flow_dissector")
-__success
+__failure __msg("cannot update sockmap in this context")
int test_flow_dissector_delete(struct __sk_buff *skb __always_unused)
{
test_sockmap_delete();
@@ -98,7 +98,7 @@ int test_flow_dissector_delete(struct __sk_buff *skb __always_unused)
}
SEC("flow_dissector")
-__failure __msg("program of this type cannot use helper bpf_sk_release")
+__failure __msg("cannot update sockmap in this context")
int test_flow_dissector_update(struct __sk_buff *skb __always_unused)
{
test_sockmap_lookup_and_update(); /* no access to skb->sk */
@@ -146,7 +146,7 @@ int test_sk_reuseport(struct sk_reuseport_md *ctx)
}
SEC("socket")
-__success
+__failure __msg("cannot update sockmap in this context")
int test_socket_filter(struct __sk_buff *skb)
{
test_sockmap_mutate(skb->sk);
@@ -179,7 +179,7 @@ int test_sockops_update_dedicated(struct bpf_sock_ops *ctx)
}
SEC("xdp")
-__success
+__failure __msg("cannot update sockmap in this context")
int test_xdp(struct xdp_md *ctx __always_unused)
{
test_sockmap_lookup_and_mutate();
--
2.43.0
^ permalink raw reply related [flat|nested] 5+ messages in thread