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When Capsicum starts creating capabilities to wrap existing file

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descriptors, we will want to allocate a new descriptor without installing
it in the FD array.

Split falloc() into falloc_noinstall() and finstall(), and rewrite
falloc() to call them with appropriate atomicity.

Approved by: mentor (rwatson), re (bz)
This commit is contained in:
jonathan 2011-06-30 15:22:49 +00:00
parent 8c932faae4
commit 4d4c5b3285
2 changed files with 60 additions and 27 deletions
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85
sys/kern/kern_descrip.c
View File

@ -1561,54 +1561,85 @@ fdavail(struct thread *td, int n)
int
falloc(struct thread *td, struct file **resultfp, int *resultfd, int flags)
{
struct proc *p = td->td_proc;
struct file *fp;
int error, i;
int error, fd;
error = falloc_noinstall(td, &fp);
if (error)
return (error); /* no reference held on error */
error = finstall(td, fp, &fd, flags);
if (error) {
fdrop(fp, td); /* one reference (fp only) */
return (error);
}
if (resultfp != NULL)
*resultfp = fp; /* copy out result */
else
fdrop(fp, td); /* release local reference */
if (resultfd != NULL)
*resultfd = fd;
return (0);
}
/*
* Create a new open file structure without allocating a file descriptor.
*/
int
falloc_noinstall(struct thread *td, struct file **resultfp)
{
struct file *fp;
int maxuserfiles = maxfiles - (maxfiles / 20);
static struct timeval lastfail;
static int curfail;
fp = uma_zalloc(file_zone, M_WAITOK | M_ZERO);
KASSERT(resultfp != NULL, ("%s: resultfp == NULL", __func__));
if ((openfiles >= maxuserfiles &&
priv_check(td, PRIV_MAXFILES) != 0) ||
openfiles >= maxfiles) {
if (ppsratecheck(&lastfail, &curfail, 1)) {
printf("kern.maxfiles limit exceeded by uid %i, please see tuning(7).\n",
td->td_ucred->cr_ruid);
printf("kern.maxfiles limit exceeded by uid %i, "
"please see tuning(7).\n", td->td_ucred->cr_ruid);
}
uma_zfree(file_zone, fp);
return (ENFILE);
}
atomic_add_int(&openfiles, 1);
/*
* If the process has file descriptor zero open, add the new file
* descriptor to the list of open files at that point, otherwise
* put it at the front of the list of open files.
*/
fp = uma_zalloc(file_zone, M_WAITOK | M_ZERO);
refcount_init(&fp->f_count, 1);
if (resultfp)
fhold(fp);
fp->f_cred = crhold(td->td_ucred);
fp->f_ops = &badfileops;
fp->f_data = NULL;
fp->f_vnode = NULL;
FILEDESC_XLOCK(p->p_fd);
if ((error = fdalloc(td, 0, &i))) {
FILEDESC_XUNLOCK(p->p_fd);
fdrop(fp, td);
if (resultfp)
fdrop(fp, td);
*resultfp = fp;
return (0);
}
/*
* Install a file in a file descriptor table.
*/
int
finstall(struct thread *td, struct file *fp, int *fd, int flags)
{
struct filedesc *fdp = td->td_proc->p_fd;
int error;
KASSERT(fd != NULL, ("%s: fd == NULL", __func__));
KASSERT(fp != NULL, ("%s: fp == NULL", __func__));
FILEDESC_XLOCK(fdp);
if ((error = fdalloc(td, 0, fd))) {
FILEDESC_XUNLOCK(fdp);
return (error);
}
p->p_fd->fd_ofiles[i] = fp;
fhold(fp);
fdp->fd_ofiles[*fd] = fp;
if ((flags & O_CLOEXEC) != 0)
p->p_fd->fd_ofileflags[i] |= UF_EXCLOSE;
FILEDESC_XUNLOCK(p->p_fd);
if (resultfp)
*resultfp = fp;
if (resultfd)
*resultfd = i;
fdp->fd_ofileflags[*fd] |= UF_EXCLOSE;
FILEDESC_XUNLOCK(fdp);
return (0);
}

2
sys/sys/filedesc.h
View File

@ -113,6 +113,8 @@ int dupfdopen(struct thread *td, struct filedesc *fdp, int indx, int dfd,
int mode, int error);
int falloc(struct thread *td, struct file **resultfp, int *resultfd,
int flags);
int falloc_noinstall(struct thread *td, struct file **resultfp);
int finstall(struct thread *td, struct file *fp, int *resultfp, int flags);
int fdalloc(struct thread *td, int minfd, int *result);
int fdavail(struct thread *td, int n);
int fdcheckstd(struct thread *td);