Date: Sun, 12 Sep 2021 12:13:52 +0300 From: Andriy Gapon <avg@freebsd.org> To: Mark Johnston <markj@freebsd.org> Cc: "net@FreeBSD.org" <net@freebsd.org>, hackers@freebsd.org Subject: Re: recvmsg() "short receive" after FIONREAD Message-ID: <c0a47189-4bd1-a572-6cf2-6eba29c53392@FreeBSD.org> In-Reply-To: <YTz4OJEsBRcuVSaN@nuc> References: <500a2272-c1b3-3f97-0096-9fe8117c4b95@FreeBSD.org> <6f455869-cbdd-ee20-f2f8-f633e22071e9@FreeBSD.org> <YTuznrhho4qGXqu8@nuc> <cdd2328e-e6aa-f0fc-a77a-adae03759f18@FreeBSD.org> <4a2165c5-b97b-8fb7-9ada-0acae3197824@FreeBSD.org> <b309f8a5-c550-905b-4340-0b7005ea6fe3@FreeBSD.org> <YTy5kRl0kDl495Po@nuc> <fcf10f8a-1672-4a21-c64b-55044cac81c5@FreeBSD.org> <4499e2b0-d1e7-5bee-519c-783fb930fc06@FreeBSD.org> <82143b59-a0e6-c23e-8b47-29d8d41eb5b4@FreeBSD.org> <YTz4OJEsBRcuVSaN@nuc>
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On 11/09/2021 21:40, Mark Johnston wrote:
> On Sat, Sep 11, 2021 at 09:25:42PM +0300, Andriy Gapon wrote:
>> So, this is what I've got:
>> diff --git a/sys/kern/sys_socket.c b/sys/kern/sys_socket.c
>> index e53b0367960b..11ee03703407 100644
>> --- a/sys/kern/sys_socket.c
>> +++ b/sys/kern/sys_socket.c
>> @@ -210,7 +210,12 @@ soo_ioctl(struct file *fp, u_long cmd, void *data, struct
>> ucred *active_cred,
>> if (SOLISTENING(so)) {
>> error = EINVAL;
>> } else {
>> - *(int *)data = sbavail(&so->so_rcv);
>> + struct sockbuf *sb;
>> +
>> + sb = &so->so_rcv;
>> + SOCKBUF_LOCK(sb);
>> + *(int *)data = sbavail(sb) - sb->sb_ctl;
>> + SOCKBUF_UNLOCK(sb);
>> }
>> break;
>
> It should use SOCK_RECVBUF_LOCK() (see
> https://cgit.freebsd.org/src/commit/?id=74a68313b503940158a2e8e8f02626d7cdbdaff9
> ):
>
> sb = &so->so_rcv;
> SOCK_RECVBUF_LOCK(so);
> if (SOLISTENING(so))
> error = EINVAL;
> else
> *(int *)data = sbavail(sb) - sb->sb_ctl;
> SOCK_RECVBUF_UNLOCK(so);
>
> Otherwise a concurrent listen(2) will clobber the pointer used by
> SOCKBUF_LOCK().
>
Oh, I see now. I haven't pulled that version yet, so I could not find
SOCK_RECVBUF_LOCK in my tree :-)
Since you have the change and you did all the thinking work anyway, could you
please commit it?
Thanks!
--
Andriy Gapon
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