fs/fcntl.c

/* */
This source file includes following definitions.
dupfd
sys_dup2
sys_dup
sys_fcntl
kill_fasync
   1 /*
   2  *  linux/fs/fcntl.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6 
   7 #include <asm/segment.h>
   8 
   9 #include <linux/sched.h>
  10 #include <linux/kernel.h>
  11 #include <linux/errno.h>
  12 #include <linux/stat.h>
  13 #include <linux/fcntl.h>
  14 #include <linux/string.h>
  15 
  16 extern int fcntl_getlk(unsigned int, struct flock *);
  17 extern int fcntl_setlk(unsigned int, unsigned int, struct flock *);
  18 extern int sock_fcntl (struct file *, unsigned int cmd, unsigned long arg);
  19 
  20 static int dupfd(unsigned int fd, unsigned int arg)
     /*  */
  21 {
  22         if (fd >= NR_OPEN || !current->files->fd[fd])
  23                 return -EBADF;
  24         if (arg >= NR_OPEN)
  25                 return -EINVAL;
  26         while (arg < NR_OPEN)
  27                 if (current->files->fd[arg])
  28                         arg++;
  29                 else
  30                         break;
  31         if (arg >= NR_OPEN)
  32                 return -EMFILE;
  33         FD_CLR(arg, &current->files->close_on_exec);
  34         (current->files->fd[arg] = current->files->fd[fd])->f_count++;
  35         return arg;
  36 }
  37 
  38 asmlinkage int sys_dup2(unsigned int oldfd, unsigned int newfd)
     /*  */
  39 {
  40         if (oldfd >= NR_OPEN || !current->files->fd[oldfd])
  41                 return -EBADF;
  42         if (newfd == oldfd)
  43                 return newfd;
  44         /*
  45          * errno's for dup2() are slightly different than for fcntl(F_DUPFD)
  46          * for historical reasons.
  47          */
  48         if (newfd > NR_OPEN)    /* historical botch - should have been >= */
  49                 return -EBADF;  /* dupfd() would return -EINVAL */
  50 #if 1
  51         if (newfd == NR_OPEN)
  52                 return -EBADF;  /* dupfd() does return -EINVAL and that may
  53                                  * even be the standard!  But that is too
  54                                  * weird for now.
  55                                  */
  56 #endif
  57         sys_close(newfd);
  58         return dupfd(oldfd,newfd);
  59 }
  60 
  61 asmlinkage int sys_dup(unsigned int fildes)
     /*  */
  62 {
  63         return dupfd(fildes,0);
  64 }
  65 
  66 asmlinkage long sys_fcntl(unsigned int fd, unsigned int cmd, unsigned long arg)
     /*  */
  67 {       
  68         struct file * filp;
  69         struct task_struct *p;
  70         int task_found = 0;
  71 
  72         if (fd >= NR_OPEN || !(filp = current->files->fd[fd]))
  73                 return -EBADF;
  74         switch (cmd) {
  75                 case F_DUPFD:
  76                         return dupfd(fd,arg);
  77                 case F_GETFD:
  78                         return FD_ISSET(fd, &current->files->close_on_exec);
  79                 case F_SETFD:
  80                         if (arg&1)
  81                                 FD_SET(fd, &current->files->close_on_exec);
  82                         else
  83                                 FD_CLR(fd, &current->files->close_on_exec);
  84                         return 0;
  85                 case F_GETFL:
  86                         return filp->f_flags;
  87                 case F_SETFL:
  88                         /*
  89                          * In the case of an append-only file, O_APPEND
  90                          * cannot be cleared
  91                          */
  92                         if (IS_APPEND(filp->f_inode) && !(arg & O_APPEND))
  93                                 return -EPERM;
  94                         if ((arg & FASYNC) && !(filp->f_flags & FASYNC) &&
  95                             filp->f_op->fasync)
  96                                 filp->f_op->fasync(filp->f_inode, filp, 1);
  97                         if (!(arg & FASYNC) && (filp->f_flags & FASYNC) &&
  98                             filp->f_op->fasync)
  99                                 filp->f_op->fasync(filp->f_inode, filp, 0);
 100                         filp->f_flags &= ~(O_APPEND | O_NONBLOCK | FASYNC);
 101                         filp->f_flags |= arg & (O_APPEND | O_NONBLOCK |
 102                                                 FASYNC);
 103                         return 0;
 104                 case F_GETLK:
 105                         return fcntl_getlk(fd, (struct flock *) arg);
 106                 case F_SETLK:
 107                         return fcntl_setlk(fd, cmd, (struct flock *) arg);
 108                 case F_SETLKW:
 109                         return fcntl_setlk(fd, cmd, (struct flock *) arg);
 110                 case F_GETOWN:
 111                         /*
 112                          * XXX If f_owner is a process group, the
 113                          * negative return value will get converted
 114                          * into an error.  Oops.  If we keep the the
 115                          * current syscall conventions, the only way
 116                          * to fix this will be in libc.
 117                          */
 118                         return filp->f_owner;
 119                 case F_SETOWN:
 120                         /*
 121                          *      Add the security checks - AC. Without
 122                          *      this there is a massive Linux security
 123                          *      hole here - consider what happens if
 124                          *      you do something like
 125                          * 
 126                          *              fcntl(0,F_SETOWN,some_root_process);
 127                          *              getchar();
 128                          * 
 129                          *      and input a line!
 130                          * 
 131                          * BTW: Don't try this for fun. Several Unix
 132                          *      systems I tried this on fall for the
 133                          *      trick!
 134                          * 
 135                          * I had to fix this botch job as Linux
 136                          *      kill_fasync asserts priv making it a
 137                          *      free all user process killer!
 138                          *
 139                          * Changed to make the security checks more
 140                          * liberal.  -- TYT
 141                          */
 142                         if (current->pgrp == -arg || current->pid == arg)
 143                                 goto fasync_ok;
 144                         
 145                         for_each_task(p) {
 146                                 if ((p->pid == arg) || (p->pid == -arg) || 
 147                                     (p->pgrp == -arg)) {
 148                                         task_found++;
 149                                         if ((p->session != current->session) &&
 150                                             (p->uid != current->uid) &&
 151                                             (p->euid != current->euid) &&
 152                                             !suser())
 153                                                 return -EPERM;
 154                                         break;
 155                                 }
 156                         }
 157                         if ((task_found == 0) && !suser())
 158                                 return -EINVAL;
 159                 fasync_ok:
 160                         filp->f_owner = arg;
 161                         if (S_ISSOCK (filp->f_inode->i_mode))
 162                                 sock_fcntl (filp, F_SETOWN, arg);
 163                         return 0;
 164                 default:
 165                         /* sockets need a few special fcntls. */
 166                         if (S_ISSOCK (filp->f_inode->i_mode))
 167                           {
 168                              return (sock_fcntl (filp, cmd, arg));
 169                           }
 170                         return -EINVAL;
 171         }
 172 }
 173 
 174 void kill_fasync(struct fasync_struct *fa, int sig)
     /*  */
 175 {
 176         while (fa) {
 177                 if (fa->magic != FASYNC_MAGIC) {
 178                         printk("kill_fasync: bad magic number in "
 179                                "fasync_struct!\n");
 180                         return;
 181                 }
 182                 if (fa->fa_file->f_owner > 0)
 183                         kill_proc(fa->fa_file->f_owner, sig, 1);
 184                 else
 185                         kill_pg(-fa->fa_file->f_owner, sig, 1);
 186                 fa = fa->fa_next;
 187         }
 188 }
/* */
root/fs/fcntl.c

DEFINITIONS
