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Remove any possibility of hiwat-related race conditions by changing

Browse source 
the chgsbsize() call to use a "subject" pointer (&sb.sb_hiwat) and
a u_long target to set it to.  The whole thing is splnet().

This fixes a problem that jdp has been able to provoke.
This commit is contained in:
Brian Feldman 2000-08-29 11:28:06 +00:00
parent 473998719e
commit 6aef685fbb
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=65198
6 changed files with 31 additions and 24 deletions
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16
sys/kern/kern_proc.c
View file

@ -194,25 +194,33 @@ chgproccnt(uid, diff, max)
* Change the total socket buffer size a user has used.
*/
int
chgsbsize(uid, diff, max)
chgsbsize(uid, hiwat, to, max)
uid_t uid;
rlim_t diff;
u_long *hiwat;
u_long to;
rlim_t max;
{
struct uidinfo *uip;
rlim_t diff;
int s;
uip = uifind(uid);
if (diff < 0)
KASSERT(uip != NULL, ("reducing sbsize: lost count, uid = %d", uid));
KASSERT(to >= *hiwat || uip != NULL,
("reducing sbsize: lost count, uid = %d", uid));
if (uip == NULL)
uip = uicreate(uid);
s = splnet();
diff = to - *hiwat;
/* don't allow them to exceed max, but allow subtraction */
if (diff > 0 && uip->ui_sbsize + diff > max) {
(void)uifree(uip);
splx(s);
return (0);
}
uip->ui_sbsize += diff;
*hiwat = to;
(void)uifree(uip);
splx(s);
return (1);
}

8
sys/kern/uipc_sockbuf.c
View file

@ -420,7 +420,6 @@ sbreserve(sb, cc, so, p)
struct socket *so;
struct proc *p;
{
rlim_t delta;
/*
* p will only be NULL when we're in an interrupt
@ -428,8 +427,7 @@ sbreserve(sb, cc, so, p)
*/
if ((u_quad_t)cc > (u_quad_t)sb_max * MCLBYTES / (MSIZE + MCLBYTES))
return (0);
delta = (rlim_t)cc - sb->sb_hiwat;
if (p && !chgsbsize(so->so_cred->cr_uid, delta,
if (p && !chgsbsize(so->so_cred->cr_uid, &sb->sb_hiwat, cc,
p->p_rlimit[RLIMIT_SBSIZE].rlim_cur)) {
return (0);
}
@ -450,8 +448,8 @@ sbrelease(sb, so)
{
sbflush(sb);
(void)chgsbsize(so->so_cred->cr_uid, -(rlim_t)sb->sb_hiwat, RLIM_INFINITY);
sb->sb_hiwat = sb->sb_mbmax = 0;
(void)chgsbsize(so->so_cred->cr_uid, &sb->sb_hiwat, 0, RLIM_INFINITY);
sb->sb_mbmax = 0;
}
/*

4
sys/kern/uipc_socket.c
View file

@ -191,10 +191,10 @@ sodealloc(so)
so->so_gencnt = ++so_gencnt;
if (so->so_rcv.sb_hiwat)
(void)chgsbsize(so->so_cred->cr_uid,
-(rlim_t)so->so_rcv.sb_hiwat, RLIM_INFINITY);
&so->so_rcv.sb_hiwat, 0, RLIM_INFINITY);
if (so->so_snd.sb_hiwat)
(void)chgsbsize(so->so_cred->cr_uid,
-(rlim_t)so->so_snd.sb_hiwat, RLIM_INFINITY);
&so->so_snd.sb_hiwat, 0, RLIM_INFINITY);
if (so->so_accf != NULL) {
if (so->so_accf->so_accept_filter != NULL &&
so->so_accf->so_accept_filter->accf_destroy != NULL) {

8
sys/kern/uipc_socket2.c
View file

@ -420,7 +420,6 @@ sbreserve(sb, cc, so, p)
struct socket *so;
struct proc *p;
{
rlim_t delta;
/*
* p will only be NULL when we're in an interrupt
@ -428,8 +427,7 @@ sbreserve(sb, cc, so, p)
*/
if ((u_quad_t)cc > (u_quad_t)sb_max * MCLBYTES / (MSIZE + MCLBYTES))
return (0);
delta = (rlim_t)cc - sb->sb_hiwat;
if (p && !chgsbsize(so->so_cred->cr_uid, delta,
if (p && !chgsbsize(so->so_cred->cr_uid, &sb->sb_hiwat, cc,
p->p_rlimit[RLIMIT_SBSIZE].rlim_cur)) {
return (0);
}
@ -450,8 +448,8 @@ sbrelease(sb, so)
{
sbflush(sb);
(void)chgsbsize(so->so_cred->cr_uid, -(rlim_t)sb->sb_hiwat, RLIM_INFINITY);
sb->sb_hiwat = sb->sb_mbmax = 0;
(void)chgsbsize(so->so_cred->cr_uid, &sb->sb_hiwat, 0, RLIM_INFINITY);
sb->sb_mbmax = 0;
}
/*

17
sys/kern/uipc_usrreq.c
View file

@ -217,6 +217,7 @@ uipc_rcvd(struct socket *so, int flags)
{
struct unpcb *unp = sotounpcb(so);
struct socket *so2;
u_long newhiwat;
if (unp == 0)
return EINVAL;
@ -235,9 +236,10 @@ uipc_rcvd(struct socket *so, int flags)
*/
so2->so_snd.sb_mbmax += unp->unp_mbcnt - so->so_rcv.sb_mbcnt;
unp->unp_mbcnt = so->so_rcv.sb_mbcnt;
so2->so_snd.sb_hiwat += unp->unp_cc - so->so_rcv.sb_cc;
(void)chgsbsize(so2->so_cred->cr_uid,
(rlim_t)unp->unp_cc - so->so_rcv.sb_cc, RLIM_INFINITY);
newhiwat = so2->so_snd.sb_hiwat + unp->unp_cc -
so->so_rcv.sb_cc;
(void)chgsbsize(so2->so_cred->cr_uid, &so2->so_snd.sb_hiwat,
newhiwat, RLIM_INFINITY);
unp->unp_cc = so->so_rcv.sb_cc;
sowwakeup(so2);
break;
@ -257,6 +259,7 @@ uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
int error = 0;
struct unpcb *unp = sotounpcb(so);
struct socket *so2;
u_long newhiwat;
if (unp == 0) {
error = EINVAL;
@ -342,10 +345,10 @@ uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
so->so_snd.sb_mbmax -=
so2->so_rcv.sb_mbcnt - unp->unp_conn->unp_mbcnt;
unp->unp_conn->unp_mbcnt = so2->so_rcv.sb_mbcnt;
so->so_snd.sb_hiwat -=
so2->so_rcv.sb_cc - unp->unp_conn->unp_cc;
(void)chgsbsize(so->so_cred->cr_uid,
(rlim_t)unp->unp_conn->unp_cc - so2->so_rcv.sb_cc, RLIM_INFINITY);
newhiwat = so->so_snd.sb_hiwat -
(so2->so_rcv.sb_cc - unp->unp_conn->unp_cc);
(void)chgsbsize(so->so_cred->cr_uid, &so->so_snd.sb_hiwat,
newhiwat, RLIM_INFINITY);
unp->unp_conn->unp_cc = so2->so_rcv.sb_cc;
sorwakeup(so2);
m = 0;

2
sys/sys/proc.h
View file

@ -422,7 +422,7 @@ struct vm_zone;
extern struct vm_zone *proc_zone;
int chgproccnt __P((uid_t uid, int diff, int max));
int chgsbsize __P((uid_t uid, rlim_t diff, rlim_t max));
int chgsbsize __P((uid_t uid, u_long *hiwat, u_long to, rlim_t max));
int enterpgrp __P((struct proc *p, pid_t pgid, int mksess));
void fixjobc __P((struct proc *p, struct pgrp *pgrp, int entering));
int inferior __P((struct proc *p));