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Fix ktrace enablement/disablement races that can result in a vnode

Browse source 
ref count panic.

Bug noticed by:	ps
Reviewed by:	ps
MFC after:	1 day
This commit is contained in:
Matthew Dillon 2001-10-24 01:05:39 +00:00
parent 3f498bf72b
commit 79deba82cd
4 changed files with 66 additions and 17 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

10
sys/kern/kern_exec.c
View file

@ -335,9 +335,13 @@ interpret:
*/
setsugid(p);
if (p->p_tracep && suser_xxx(oldcred, NULL, PRISON_ROOT)) {
p->p_traceflag = 0;
vrele(p->p_tracep);
p->p_tracep = NULL;
struct vnode *vtmp;
if ((vtmp = p->p_tracep) != NULL) {
p->p_tracep = NULL;
p->p_traceflag = 0;
vrele(vtmp);
}
}
/*
* Set the new credentials.

7
sys/kern/kern_exit.c
View file

@ -124,6 +124,7 @@ exit1(td, rv)
struct proc *p = td->td_proc;
register struct proc *q, *nq;
register struct vmspace *vm;
struct vnode *vtmp;
struct exitlist *ep;
GIANT_REQUIRED;
@ -275,8 +276,10 @@ exit1(td, rv)
* release trace file
*/
p->p_traceflag = 0; /* don't trace the vrele() */
if (p->p_tracep)
vrele(p->p_tracep);
if ((vtmp = p->p_tracep) != NULL) {
p->p_tracep = NULL;
vrele(vtmp);
}
#endif
/*
* Remove proc from allproc queue and pidhash chain.

7
sys/kern/kern_fork.c
View file

@ -585,10 +585,11 @@ again:
PROC_LOCK(p1);
#ifdef KTRACE
/*
* Copy traceflag and tracefile if enabled.
* If not inherited, these were zeroed above.
* Copy traceflag and tracefile if enabled. If not inherited,
* these were zeroed above but we still could have a trace race
* so make sure p2's p_tracep is NULL.
*/
if (p1->p_traceflag & KTRFAC_INHERIT) {
if ((p1->p_traceflag & KTRFAC_INHERIT) && p2->p_tracep == NULL) {
p2->p_traceflag = p1->p_traceflag;
if ((p2->p_tracep = p1->p_tracep) != NULL) {
PROC_UNLOCK(p1);

59
sys/kern/kern_ktrace.c
View file

@ -150,12 +150,19 @@ ktrnamei(vp, path)
struct ktr_header *kth;
struct proc *p = curproc; /* XXX */
/*
* don't let p_tracep get ripped out from under us
*/
if (vp)
VREF(vp);
p->p_traceflag |= KTRFAC_ACTIVE;
kth = ktrgetheader(KTR_NAMEI);
kth->ktr_len = strlen(path);
kth->ktr_buffer = path;
ktrwrite(vp, kth, NULL);
if (vp)
vrele(vp);
FREE(kth, M_KTRACE);
p->p_traceflag &= ~KTRFAC_ACTIVE;
}
@ -174,6 +181,11 @@ ktrgenio(vp, fd, rw, uio, error)
if (error)
return;
/*
* don't let p_tracep get ripped out from under us
*/
if (vp)
VREF(vp);
p->p_traceflag |= KTRFAC_ACTIVE;
kth = ktrgetheader(KTR_GENIO);
ktg.ktr_fd = fd;
@ -184,6 +196,8 @@ ktrgenio(vp, fd, rw, uio, error)
uio->uio_rw = UIO_WRITE;
ktrwrite(vp, kth, uio);
if (vp)
vrele(vp);
FREE(kth, M_KTRACE);
p->p_traceflag &= ~KTRFAC_ACTIVE;
}
@ -200,6 +214,11 @@ ktrpsig(vp, sig, action, mask, code)
struct ktr_psig kp;
struct proc *p = curproc; /* XXX */
/*
* don't let vp get ripped out from under us
*/
if (vp)
VREF(vp);
p->p_traceflag |= KTRFAC_ACTIVE;
kth = ktrgetheader(KTR_PSIG);
kp.signo = (char)sig;
@ -210,6 +229,8 @@ ktrpsig(vp, sig, action, mask, code)
kth->ktr_len = sizeof (struct ktr_psig);
ktrwrite(vp, kth, NULL);
if (vp)
vrele(vp);
FREE(kth, M_KTRACE);
p->p_traceflag &= ~KTRFAC_ACTIVE;
}
@ -223,6 +244,11 @@ ktrcsw(vp, out, user)
struct ktr_csw kc;
struct proc *p = curproc; /* XXX */
/*
* don't let vp get ripped out from under us
*/
if (vp)
VREF(vp);
p->p_traceflag |= KTRFAC_ACTIVE;
kth = ktrgetheader(KTR_CSW);
kc.out = out;
@ -231,6 +257,8 @@ ktrcsw(vp, out, user)
kth->ktr_len = sizeof (struct ktr_csw);
ktrwrite(vp, kth, NULL);
if (vp)
vrele(vp);
FREE(kth, M_KTRACE);
p->p_traceflag &= ~KTRFAC_ACTIVE;
}
@ -289,19 +317,20 @@ ktrace(td, uap)
}
}
/*
* Clear all uses of the tracefile
* Clear all uses of the tracefile.
*/
if (ops == KTROP_CLEARFILE) {
sx_slock(&allproc_lock);
LIST_FOREACH(p, &allproc, p_list) {
if (p->p_tracep == vp) {
if (ktrcanset(curp, p)) {
if (ktrcanset(curp, p) && p->p_tracep == vp) {
p->p_tracep = NULL;
p->p_traceflag = 0;
(void) vn_close(vp, FREAD|FWRITE,
p->p_ucred, td);
} else
} else {
error = EPERM;
}
}
}
sx_sunlock(&allproc_lock);
@ -371,6 +400,7 @@ utrace(td, uap)
#ifdef KTRACE
struct ktr_header *kth;
struct proc *p = curproc; /* XXX */
struct vnode *vp;
register caddr_t cp;
if (!KTRPOINT(p, KTR_USER))
@ -378,13 +408,17 @@ utrace(td, uap)
if (uap->len > KTR_USER_MAXLEN)
return (EINVAL);
p->p_traceflag |= KTRFAC_ACTIVE;
if ((vp = p->p_tracep) != NULL)
VREF(vp);
kth = ktrgetheader(KTR_USER);
MALLOC(cp, caddr_t, uap->len, M_KTRACE, M_WAITOK);
if (!copyin(uap->addr, cp, uap->len)) {
kth->ktr_buffer = cp;
kth->ktr_len = uap->len;
ktrwrite(p->p_tracep, kth, NULL);
ktrwrite(vp, kth, NULL);
}
if (vp)
vrele(vp);
FREE(kth, M_KTRACE);
FREE(cp, M_KTRACE);
p->p_traceflag &= ~KTRFAC_ACTIVE;
@ -407,12 +441,16 @@ ktrops(curp, p, ops, facs, vp)
return (0);
if (ops == KTROP_SET) {
if (p->p_tracep != vp) {
struct vnode *vtmp;
/*
* if trace file already in use, relinquish
*/
if (p->p_tracep != NULL)
vrele(p->p_tracep);
VREF(vp);
while ((vtmp = p->p_tracep) != NULL) {
p->p_tracep = NULL;
vrele(vtmp);
}
p->p_tracep = vp;
}
p->p_traceflag |= facs;
@ -421,11 +459,13 @@ ktrops(curp, p, ops, facs, vp)
} else {
/* KTROP_CLEAR */
if (((p->p_traceflag &= ~facs) & KTRFAC_MASK) == 0) {
struct vnode *vtmp;
/* no more tracing */
p->p_traceflag = 0;
if (p->p_tracep != NULL) {
vrele(p->p_tracep);
if ((vtmp = p->p_tracep) != NULL) {
p->p_tracep = NULL;
vrele(vtmp);
}
}
}
@ -513,7 +553,8 @@ ktrwrite(vp, kth, uio)
if (!error)
return;
/*
* If error encountered, give up tracing on this vnode.
* If error encountered, give up tracing on this vnode. XXX what
* happens to the loop if vrele() blocks?
*/
log(LOG_NOTICE, "ktrace write failed, errno %d, tracing stopped\n",
error);