When we specify apply_bytes, we divide the msg into multiple segments, each with a length of 'send', and every time we send this part of the data using tcp_bpf_sendmsg_redir(), we use sk_msg_return_zero() to uncharge the memory of the specified 'send' size.

However, if the first segment of data fails to send, for example, the peer's buffer is full, we need to release all of the msg. When releasing the msg, we haven't uncharged the memory of the subsequent segments.

This modification does not make significant logical changes, but only fills in the missing uncharge places.

This issue has existed all along, until it was exposed after we added the apply test in test_sockmap: commit 3448ad23b34e ("selftests/bpf: Add apply_bytes test to test_txmsg_redir_wait_sndmem in test_sockmap")

Reported-by: Cong Wang xiyou.wangcong@gmail.com Closes: https://lore.kernel.org/bpf/aAmIi0vlycHtbXeb@pop-os.localdomain/T/#t Fixes: d3b18ad31f93 ("tls: add bpf support to sk_msg handling") Signed-off-by: Jiayuan Chen jiayuan.chen@linux.dev --- net/tls/tls_sw.c | 7 +++++++ 1 file changed, 7 insertions(+)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c index f3d7d19482da..fc88e34b7f33 100644 --- a/net/tls/tls_sw.c +++ b/net/tls/tls_sw.c @@ -908,6 +908,13 @@ static int bpf_exec_tx_verdict(struct sk_msg *msg, struct sock *sk, &msg_redir, send, flags); lock_sock(sk); if (err < 0) { + /* Regardless of whether the data represented by + * msg_redir is sent successfully, we have already + * uncharged it via sk_msg_return_zero(). The + * msg->sg.size represents the remaining unprocessed + * data, which needs to be uncharged here. + */ + sk_mem_uncharge(sk, msg->sg.size); *copied -= sk_msg_free_nocharge(sk, &msg_redir); msg->sg.size = 0; }

The selftest can reproduce an issue where we miss the uncharge operation when freeing msg, which will cause the following warning. We fixed the issue and added this reproducer to selftest to ensure it will not happen again.

------------[ cut here ]------------ WARNING: CPU: 1 PID: 40 at net/ipv4/af_inet.c inet_sock_destruct+0x173/0x1d5 Tainted: [W]=WARN Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014 Workqueue: events sk_psock_destroy RIP: 0010:inet_sock_destruct+0x173/0x1d5 RSP: 0018:ffff8880085cfc18 EFLAGS: 00010202 RAX: 1ffff11003dbfc00 RBX: ffff88801edfe3e8 RCX: ffffffff822f5af4 RDX: 0000000000000007 RSI: dffffc0000000000 RDI: ffff88801edfe16c RBP: ffff88801edfe184 R08: ffffed1003dbfc31 R09: 0000000000000000 R10: ffffffff822f5ab7 R11: ffff88801edfe187 R12: ffff88801edfdec0 R13: ffff888020376ac0 R14: ffff888020376ac0 R15: ffff888020376a60 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000556365155830 CR3: 000000001d6aa000 CR4: 0000000000350ef0 Call Trace: <TASK> __sk_destruct+0x46/0x222 sk_psock_destroy+0x22f/0x242 process_one_work+0x504/0x8a8 ? process_one_work+0x39d/0x8a8 ? __pfx_process_one_work+0x10/0x10 ? worker_thread+0x44/0x2ae ? __list_add_valid_or_report+0x83/0xea ? srso_return_thunk+0x5/0x5f ? __list_add+0x45/0x52 process_scheduled_works+0x73/0x82 worker_thread+0x1ce/0x2ae

Signed-off-by: Jiayuan Chen jiayuan.chen@linux.dev --- .../selftests/bpf/prog_tests/sockmap_ktls.c | 76 +++++++++++++++++++ .../selftests/bpf/progs/test_sockmap_ktls.c | 10 +++ 2 files changed, 86 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_ktls.c b/tools/testing/selftests/bpf/prog_tests/sockmap_ktls.c index 49b85c1c7552..8f07168c9de6 100644 --- a/tools/testing/selftests/bpf/prog_tests/sockmap_ktls.c +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_ktls.c @@ -306,6 +306,80 @@ static void test_sockmap_ktls_tx_cork(int family, int sotype, bool push) test_sockmap_ktls__destroy(skel); }

+static void test_sockmap_ktls_tx_no_buf(int family, int sotype, bool push) +{ + int c = 0, p = 0, one = 1, two = 2; + struct test_sockmap_ktls *skel; + unsigned char *data = NULL; + struct msghdr msg = {0}; + struct iovec iov[2]; + int prog_fd, map_fd; + int txrx_buf = 1024; + int iov_length = 8192; + int err; + + skel = test_sockmap_ktls__open_and_load(); + if (!ASSERT_TRUE(skel, "open ktls skel")) + return; + + err = create_pair(family, sotype, &c, &p); + if (!ASSERT_OK(err, "create_pair()")) + goto out; + + err = setsockopt(c, SOL_SOCKET, SO_RCVBUFFORCE, &txrx_buf, sizeof(int)); + err |= setsockopt(p, SOL_SOCKET, SO_SNDBUFFORCE, &txrx_buf, sizeof(int)); + if (!ASSERT_OK(err, "set buf limit")) + goto out; + + prog_fd = bpf_program__fd(skel->progs.prog_sk_policy_redir); + map_fd = bpf_map__fd(skel->maps.sock_map); + + err = bpf_prog_attach(prog_fd, map_fd, BPF_SK_MSG_VERDICT, 0); + if (!ASSERT_OK(err, "bpf_prog_attach sk msg")) + goto out; + + err = bpf_map_update_elem(map_fd, &one, &c, BPF_NOEXIST); + if (!ASSERT_OK(err, "bpf_map_update_elem(c)")) + goto out; + + err = bpf_map_update_elem(map_fd, &two, &p, BPF_NOEXIST); + if (!ASSERT_OK(err, "bpf_map_update_elem(p)")) + goto out; + + skel->bss->apply_bytes = 1024; + + err = init_ktls_pairs(c, p); + if (!ASSERT_OK(err, "init_ktls_pairs(c, p)")) + goto out; + + data = calloc(iov_length, sizeof(char)); + if (!data) + goto out; + + iov[0].iov_base = data; + iov[0].iov_len = iov_length; + iov[1].iov_base = data; + iov[1].iov_len = iov_length; + msg.msg_iov = iov; + msg.msg_iovlen = 2; + + for (;;) { + err = sendmsg(c, &msg, MSG_DONTWAIT); + if (err <= 0) + break; + } + +out: + if (data) + free(data); + if (c) + close(c); + if (p) + close(p); + + test_sockmap_ktls__destroy(skel); +} + static void run_tests(int family, enum bpf_map_type map_type) { int map; @@ -330,6 +404,8 @@ static void run_ktls_test(int family, int sotype) test_sockmap_ktls_tx_cork(family, sotype, false); if (test__start_subtest("tls tx cork with push")) test_sockmap_ktls_tx_cork(family, sotype, true); + if (test__start_subtest("tls tx egress with no buf")) + test_sockmap_ktls_tx_no_buf(family, sotype, true); }

void test_sockmap_ktls(void) diff --git a/tools/testing/selftests/bpf/progs/test_sockmap_ktls.c b/tools/testing/selftests/bpf/progs/test_sockmap_ktls.c index e0f757929ef4..8bdb9987c0c7 100644 --- a/tools/testing/selftests/bpf/progs/test_sockmap_ktls.c +++ b/tools/testing/selftests/bpf/progs/test_sockmap_ktls.c @@ -6,6 +6,7 @@ int cork_byte; int push_start; int push_end; +int apply_bytes;

struct { __uint(type, BPF_MAP_TYPE_SOCKMAP); @@ -24,3 +25,12 @@ int prog_sk_policy(struct sk_msg_md *msg)

return SK_PASS; } + +SEC("sk_msg") +int prog_sk_policy_redir(struct sk_msg_md *msg) +{ + int two = 2; + + bpf_msg_apply_bytes(msg, apply_bytes); + return bpf_msg_redirect_map(msg, &sock_map, two, 0); +}