[src/netbsd-1-5]: src/sys/kern Pull up revision 1.75 (via patch, requested by...

[he <he%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/3ac5fe844c11
branches:  netbsd-1-5
changeset: 491870:3ac5fe844c11
user:      he <he%NetBSD.org@localhost>
date:      Sun Jun 10 18:22:45 2001 +0000

description:
Pull up revision 1.75 (via patch, requested by thorpej):
  Change fdalloc() to return ERESTART if reallocation of the
  descriptor array was needed, and change uses to handle that
  condition.  Make finishdup() close the descriptor in the new slot
  if it exists, and change sys_dup2() accordingly.  Closes a race
  condition when using kernel-assisted user threads.

diffstat:

 sys/kern/kern_descrip.c |  61 ++++++++++++++++++++++++++++++++++++------------
 1 files changed, 45 insertions(+), 16 deletions(-)

diffs (179 lines):

diff -r 76d5802ee4b3 -r 3ac5fe844c11 sys/kern/kern_descrip.c
--- a/sys/kern/kern_descrip.c   Sun Jun 10 18:21:28 2001 +0000
+++ b/sys/kern/kern_descrip.c   Sun Jun 10 18:22:45 2001 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_descrip.c,v 1.67.4.2 2000/08/26 00:58:35 mrg Exp $        */
+/*     $NetBSD: kern_descrip.c,v 1.67.4.3 2001/06/10 18:22:45 he Exp $ */
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1991, 1993
@@ -130,6 +130,7 @@
        int new;
        int error;
 
+ restart:
        if ((u_int)old >= fdp->fd_nfiles ||
            (fp = fdp->fd_ofiles[old]) == NULL ||
            (fp->f_iflags & FIF_WANTCLOSE) != 0)
@@ -139,6 +140,8 @@
 
        if ((error = fdalloc(p, 0, &new)) != 0) {
                FILE_UNUSE(fp, p);
+               if (error == ERESTART)
+                       goto restart;
                return (error);
        }
 
@@ -165,6 +168,7 @@
        int old = SCARG(uap, from), new = SCARG(uap, to);
        int i, error;
 
+ restart:
        if ((u_int)old >= fdp->fd_nfiles ||
            (fp = fdp->fd_ofiles[old]) == NULL ||
            (fp->f_iflags & FIF_WANTCLOSE) != 0 ||
@@ -181,14 +185,19 @@
        if (new >= fdp->fd_nfiles) {
                if ((error = fdalloc(p, new, &i)) != 0) {
                        FILE_UNUSE(fp, p);
+                       if (error == ERESTART)
+                               goto restart;
                        return (error);
                }
                if (new != i)
                        panic("dup2: fdalloc");
-       } else {
-               (void) fdrelease(p, new);
        }
 
+       /*
+        * finishdup() will close the file that's in the `new'
+        * slot, if there's one there.
+        */
+
        /* finishdup() will unuse the descriptors for us */
        return (finishdup(p, old, new, retval));
 }
@@ -218,6 +227,7 @@
        struct flock fl;
        int newmin;
 
+ restart:
        if ((u_int)fd >= fdp->fd_nfiles ||
            (fp = fdp->fd_ofiles[fd]) == NULL ||
            (fp->f_iflags & FIF_WANTCLOSE) != 0)
@@ -240,8 +250,13 @@
                        error = EINVAL;
                        goto out;
                }
-               if ((error = fdalloc(p, newmin, &i)) != 0)
+               if ((error = fdalloc(p, newmin, &i)) != 0) {
+                       if (error == ERESTART) {
+                               FILE_UNUSE(fp, p);
+                               goto restart;
+                       }
                        goto out;
+               }
 
                /* finishdup() will unuse the descriptors for us */
                return (finishdup(p, fd, i, retval));
@@ -402,19 +417,34 @@
        register_t *retval;
 {
        struct filedesc *fdp = p->p_fd;
-       struct file *fp;
+       struct file     *fp, *delfp;
 
        /*
+        * If there is a file in the new slot, remember it so we
+        * can close it after we've finished the dup.  We need
+        * to do it after the dup is finished, since closing
+        * the file may block.
+        *
         * Note: `old' is already used for us.
         */
+       delfp = fdp->fd_ofiles[new];
 
        fp = fdp->fd_ofiles[old];
        fdp->fd_ofiles[new] = fp;
        fdp->fd_ofileflags[new] = fdp->fd_ofileflags[old] &~ UF_EXCLOSE;
        fp->f_count++;
-       fd_used(fdp, new);
+       /*
+        * Note, don't have to mark it "used" in the table if there
+        * was already a file in the `new' slot.
+        */
+       if (delfp == NULL)
+               fd_used(fdp, new);
        *retval = new;
        FILE_UNUSE(fp, p);
+       if (delfp != NULL) {
+               FILE_USE(delfp);
+               (void) closef(delfp, p);
+       }
        return (0);
 }
 
@@ -435,7 +465,6 @@
 {
        struct filedesc *fdp = p->p_fd;
        struct file **fpp, *fp;
-       char *pf;
 
        fpp = &fdp->fd_ofiles[fd];
        fp = *fpp;
@@ -444,13 +473,8 @@
 
        FILE_USE(fp);
 
-       pf = &fdp->fd_ofileflags[fd];
-       if (*pf & UF_MAPPED) {
-               /* XXX: USELESS? XXXCDC check it */
-               p->p_fd->fd_ofileflags[fd] &= ~UF_MAPPED;
-       }
        *fpp = NULL;
-       *pf = 0;
+       fdp->fd_ofileflags[fd] = 0;
        fd_unused(fdp, fd);
        return (closef(fp, p));
 }
@@ -585,7 +609,7 @@
 {
        struct filedesc *fdp = p->p_fd;
        int i;
-       int lim, last, nfiles;
+       int lim, last, nfiles, rv = 0;
        struct file **newofile;
        char *newofileflags;
 
@@ -605,7 +629,7 @@
                                if (want <= fdp->fd_freefile)
                                        fdp->fd_freefile = i;
                                *result = i;
-                               return (0);
+                               return (rv);
                        }
                }
 
@@ -618,6 +642,7 @@
                        nfiles = NDEXTENT;
                else
                        nfiles = 2 * fdp->fd_nfiles;
+               rv = ERESTART;
                newofile = malloc(nfiles * OFILESIZE, M_FILEDESC, M_WAITOK);
                newofileflags = (char *) &newofile[nfiles];
                /*
@@ -690,8 +715,12 @@
        struct file *fp, *fq;
        int error, i;
 
-       if ((error = fdalloc(p, 0, &i)) != 0)
+ restart:
+       if ((error = fdalloc(p, 0, &i)) != 0) {
+               if (error == ERESTART)
+                       goto restart;
                return (error);
+       }
        if (nfiles >= maxfiles) {
                tablefull("file", "increase kern.maxfiles or MAXFILES");
                return (ENFILE);