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Don't check rcv sockbuf limits when sending on a unix stream socket.

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sosend_generic() performs an initial comparison of the amount of data
(including control messages) to be transmitted with the send buffer
size. When transmitting on a unix socket, we then compare the amount
of data being sent with the amount of space in the receive buffer size;
if insufficient space is available, sbappendcontrol() returns an error
and the data is lost.  This is easily triggered by sending control
messages together with an amount of data roughly equal to the send
buffer size, since the control message size may change in uipc_send()
as file descriptors are internalized.

Fix the problem by removing the space check in sbappendcontrol(),
whose only consumer is the unix sockets code.  The stream sockets code
uses the SB_STOP mechanism to ensure that senders will block if the
receive buffer fills up.

PR:		181741
MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D16515
This commit is contained in:
Mark Johnston 2018-08-04 20:26:54 +00:00
parent e62ca80bde
commit 5b0480f2cc
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=337328
3 changed files with 19 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
sys/kern/uipc_sockbuf.c
View File

@ -955,21 +955,14 @@ sbappendaddr(struct sockbuf *sb, const struct sockaddr *asa,
return (retval);
}
int
void
sbappendcontrol_locked(struct sockbuf *sb, struct mbuf *m0,
struct mbuf *control)
{
struct mbuf *m, *n, *mlast;
int space;
struct mbuf *m, *mlast;
SOCKBUF_LOCK_ASSERT(sb);
space = m_length(control, &n) + m_length(m0, NULL);
if (space > sbspace(sb))
return (0);
m_clrprotoflags(m0);
n->m_next = m0; /* concatenate data to control */
m_last(control)->m_next = m0;
SBLASTRECORDCHK(sb);
@ -983,18 +976,15 @@ sbappendcontrol_locked(struct sockbuf *sb, struct mbuf *m0,
SBLASTMBUFCHK(sb);
SBLASTRECORDCHK(sb);
return (1);
}
int
void
sbappendcontrol(struct sockbuf *sb, struct mbuf *m0, struct mbuf *control)
{
int retval;
SOCKBUF_LOCK(sb);
retval = sbappendcontrol_locked(sb, m0, control);
sbappendcontrol_locked(sb, m0, control);
SOCKBUF_UNLOCK(sb);
return (retval);
}
/*

24
sys/kern/uipc_usrreq.c
View File

@ -1174,16 +1174,22 @@ uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
unp2->unp_flags &= ~UNP_WANTCRED;
control = unp_addsockcred(td, control);
}
/*
* Send to paired receive port, and then reduce send buffer
* hiwater marks to maintain backpressure. Wake up readers.
* Send to paired receive port and wake up readers. Don't
* check for space available in the receive buffer if we're
* attaching ancillary data; Unix domain sockets only check
* for space in the sending sockbuf, and that check is
* performed one level up the stack. At that level we cannot
* precisely account for the amount of buffer space used
* (e.g., because control messages are not yet internalized).
*/
switch (so->so_type) {
case SOCK_STREAM:
if (control != NULL) {
if (sbappendcontrol_locked(&so2->so_rcv, m,
control))
control = NULL;
sbappendcontrol_locked(&so2->so_rcv, m,
control);
control = NULL;
} else
sbappend_locked(&so2->so_rcv, m, flags);
break;
@ -1192,14 +1198,8 @@ uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
const struct sockaddr *from;
from = &sun_noname;
/*
* Don't check for space available in so2->so_rcv.
* Unix domain sockets only check for space in the
* sending sockbuf, and that check is performed one
* level up the stack.
*/
if (sbappendaddr_nospacecheck_locked(&so2->so_rcv,
from, m, control))
from, m, control))
control = NULL;
break;
}

4
sys/sys/sockbuf.h
View File

@ -139,9 +139,9 @@ int sbappendaddr_locked(struct sockbuf *sb, const struct sockaddr *asa,
struct mbuf *m0, struct mbuf *control);
int sbappendaddr_nospacecheck_locked(struct sockbuf *sb,
const struct sockaddr *asa, struct mbuf *m0, struct mbuf *control);
int sbappendcontrol(struct sockbuf *sb, struct mbuf *m0,
void sbappendcontrol(struct sockbuf *sb, struct mbuf *m0,
struct mbuf *control);
int sbappendcontrol_locked(struct sockbuf *sb, struct mbuf *m0,
void sbappendcontrol_locked(struct sockbuf *sb, struct mbuf *m0,
struct mbuf *control);
void sbappendrecord(struct sockbuf *sb, struct mbuf *m0);
void sbappendrecord_locked(struct sockbuf *sb, struct mbuf *m0);