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af_unix: Don't set err in unix_stream_read_generic unless there was an error 

The present unix_stream_read_generic contains various code sequences of
the form

err = -EDISASTER;
if (<test>)
	goto out;

This has the unfortunate side effect of possibly causing the error code
to bleed through to the final

out:
	return copied ? : err;

and then to be wrongly returned if no data was copied because the caller
didn't supply a data buffer, as demonstrated by the program available at

http://pad.lv/1540731

Change it such that err is only set if an error condition was detected.

Fixes: 3822b5c2fc ("af_unix: Revert 'lock_interruptible' in stream receive code")
Reported-by: Joseph Salisbury <joseph.salisbury@canonical.com>
Signed-off-by: Rainer Weikusat <rweikusat@mobileactivedefense.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Rainer Weikusat 2016-02-08 18:47:19 +00:00 committed by David S. Miller
parent db92ea5d4d
commit 1b92ee3d03
1 changed files with 10 additions and 6 deletions
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16
net/unix/af_unix.c
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@ -2277,13 +2277,15 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state)
size_t size = state->size;
unsigned int last_len;
err = -EINVAL;
if (sk->sk_state != TCP_ESTABLISHED)
if (unlikely(sk->sk_state != TCP_ESTABLISHED)) {
err = -EINVAL;
goto out;
}
err = -EOPNOTSUPP;
if (flags & MSG_OOB)
if (unlikely(flags & MSG_OOB)) {
err = -EOPNOTSUPP;
goto out;
}
target = sock_rcvlowat(sk, flags & MSG_WAITALL, size);
timeo = sock_rcvtimeo(sk, noblock);
@ -2329,9 +2331,11 @@ again:
goto unlock;
unix_state_unlock(sk);
err = -EAGAIN;
if (!timeo)
if (!timeo) {
err = -EAGAIN;
break;
}
mutex_unlock(&u->readlock);
timeo = unix_stream_data_wait(sk, timeo, last,