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af_unix: Stop recv(MSG_PEEK) at consumed OOB skb.

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After consuming OOB data, recv() reading the preceding data must break at
the OOB skb regardless of MSG_PEEK.

Currently, MSG_PEEK does not stop recv() for AF_UNIX, and the behaviour is
not compliant with TCP.

  >>> from socket import *
  >>> c1, c2 = socketpair(AF_UNIX)
  >>> c1.send(b'hello', MSG_OOB)
  5
  >>> c1.send(b'world')
  5
  >>> c2.recv(1, MSG_OOB)
  b'o'
  >>> c2.recv(9, MSG_PEEK)  # This should return b'hell'
  b'hellworld'              # even with enough buffer.

Let's fix it by returning NULL for consumed skb and unlinking it only if
MSG_PEEK is not specified.

This patch also adds test cases that add recv(MSG_PEEK) before each recv().

Without fix:

  #  RUN           msg_oob.peek.oob_ahead_break ...
  # msg_oob.c:134:oob_ahead_break:AF_UNIX :hellworld
  # msg_oob.c:135:oob_ahead_break:Expected:hell
  # msg_oob.c:137:oob_ahead_break:Expected ret[0] (9) == expected_len (4)
  # oob_ahead_break: Test terminated by assertion
  #          FAIL  msg_oob.peek.oob_ahead_break
  not ok 13 msg_oob.peek.oob_ahead_break

With fix:

  #  RUN           msg_oob.peek.oob_ahead_break ...
  #            OK  msg_oob.peek.oob_ahead_break
  ok 13 msg_oob.peek.oob_ahead_break

Fixes: 314001f0bf ("af_unix: Add OOB support")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Kuniyuki Iwashima 2024-06-24 18:36:37 -07:00 • committed by Paolo Abeni
parent d098d77232
commit b94038d841
2 changed files with 29 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

9
net/unix/af_unix.c
View file

@ -2613,9 +2613,12 @@ static struct sk_buff *manage_oob(struct sk_buff *skb, struct sock *sk,
{ {
struct unix_sock *u = unix_sk(sk); struct unix_sock *u = unix_sk(sk);
if (!unix_skb_len(skb) && !(flags & MSG_PEEK)) { if (!unix_skb_len(skb)) {
skb_unlink(skb, &sk->sk_receive_queue); if (!(flags & MSG_PEEK)) {
consume_skb(skb); skb_unlink(skb, &sk->sk_receive_queue);
consume_skb(skb);
}
skb = NULL; skb = NULL;
} else { } else {
struct sk_buff *unlinked_skb = NULL; struct sk_buff *unlinked_skb = NULL;

25
tools/testing/selftests/net/af_unix/msg_oob.c
View file

@ -21,6 +21,21 @@ FIXTURE(msg_oob)
*/ */
}; };
FIXTURE_VARIANT(msg_oob)
{
bool peek;
};
FIXTURE_VARIANT_ADD(msg_oob, no_peek)
{
.peek = false,
};
FIXTURE_VARIANT_ADD(msg_oob, peek)
{
.peek = true
};
static void create_unix_socketpair(struct __test_metadata *_metadata, static void create_unix_socketpair(struct __test_metadata *_metadata,
FIXTURE_DATA(msg_oob) *self) FIXTURE_DATA(msg_oob) *self)
{ {
@ -156,8 +171,14 @@ static void __recvpair(struct __test_metadata *_metadata,
__sendpair(_metadata, self, buf, len, flags) __sendpair(_metadata, self, buf, len, flags)
#define recvpair(expected_buf, expected_len, buf_len, flags) \ #define recvpair(expected_buf, expected_len, buf_len, flags) \
__recvpair(_metadata, self, \ do { \
expected_buf, expected_len, buf_len, flags) if (variant->peek) \
__recvpair(_metadata, self, \
expected_buf, expected_len, \
buf_len, (flags) | MSG_PEEK); \
__recvpair(_metadata, self, \
expected_buf, expected_len, buf_len, flags); \
} while (0)
TEST_F(msg_oob, non_oob) TEST_F(msg_oob, non_oob)
{ {