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 inline 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         if (newfd >= NR_OPEN)
  45                 return -EBADF;  /* following POSIX.1 6.2.1 */
  46 
  47         sys_close(newfd);
  48         return dupfd(oldfd,newfd);
  49 }
  50 
  51 asmlinkage int sys_dup(unsigned int fildes)
     /*  */
  52 {
  53         return dupfd(fildes,0);
  54 }
  55 
  56 asmlinkage long sys_fcntl(unsigned int fd, unsigned int cmd, unsigned long arg)
     /*  */
  57 {       
  58         struct file * filp;
  59         struct task_struct *p;
  60         int task_found = 0;
  61 
  62         if (fd >= NR_OPEN || !(filp = current->files->fd[fd]))
  63                 return -EBADF;
  64         switch (cmd) {
  65                 case F_DUPFD:
  66                         return dupfd(fd,arg);
  67                 case F_GETFD:
  68                         return FD_ISSET(fd, &current->files->close_on_exec);
  69                 case F_SETFD:
  70                         if (arg&1)
  71                                 FD_SET(fd, &current->files->close_on_exec);
  72                         else
  73                                 FD_CLR(fd, &current->files->close_on_exec);
  74                         return 0;
  75                 case F_GETFL:
  76                         return filp->f_flags;
  77                 case F_SETFL:
  78                         /*
  79                          * In the case of an append-only file, O_APPEND
  80                          * cannot be cleared
  81                          */
  82                         if (IS_APPEND(filp->f_inode) && !(arg & O_APPEND))
  83                                 return -EPERM;
  84                         if ((arg & FASYNC) && !(filp->f_flags & FASYNC) &&
  85                             filp->f_op->fasync)
  86                                 filp->f_op->fasync(filp->f_inode, filp, 1);
  87                         if (!(arg & FASYNC) && (filp->f_flags & FASYNC) &&
  88                             filp->f_op->fasync)
  89                                 filp->f_op->fasync(filp->f_inode, filp, 0);
  90                         filp->f_flags &= ~(O_APPEND | O_NONBLOCK | FASYNC);
  91                         filp->f_flags |= arg & (O_APPEND | O_NONBLOCK |
  92                                                 FASYNC);
  93                         return 0;
  94                 case F_GETLK:
  95                         return fcntl_getlk(fd, (struct flock *) arg);
  96                 case F_SETLK:
  97                         return fcntl_setlk(fd, cmd, (struct flock *) arg);
  98                 case F_SETLKW:
  99                         return fcntl_setlk(fd, cmd, (struct flock *) arg);
 100                 case F_GETOWN:
 101                         /*
 102                          * XXX If f_owner is a process group, the
 103                          * negative return value will get converted
 104                          * into an error.  Oops.  If we keep the the
 105                          * current syscall conventions, the only way
 106                          * to fix this will be in libc.
 107                          */
 108                         return filp->f_owner;
 109                 case F_SETOWN:
 110                         /*
 111                          *      Add the security checks - AC. Without
 112                          *      this there is a massive Linux security
 113                          *      hole here - consider what happens if
 114                          *      you do something like
 115                          * 
 116                          *              fcntl(0,F_SETOWN,some_root_process);
 117                          *              getchar();
 118                          * 
 119                          *      and input a line!
 120                          * 
 121                          * BTW: Don't try this for fun. Several Unix
 122                          *      systems I tried this on fall for the
 123                          *      trick!
 124                          * 
 125                          * I had to fix this botch job as Linux
 126                          *      kill_fasync asserts priv making it a
 127                          *      free all user process killer!
 128                          *
 129                          * Changed to make the security checks more
 130                          * liberal.  -- TYT
 131                          */
 132                         if (current->pgrp == -arg || current->pid == arg)
 133                                 goto fasync_ok;
 134                         
 135                         for_each_task(p) {
 136                                 if ((p->pid == arg) || (p->pid == -arg) || 
 137                                     (p->pgrp == -arg)) {
 138                                         task_found++;
 139                                         if ((p->session != current->session) &&
 140                                             (p->uid != current->uid) &&
 141                                             (p->euid != current->euid) &&
 142                                             !suser())
 143                                                 return -EPERM;
 144                                         break;
 145                                 }
 146                         }
 147                         if ((task_found == 0) && !suser())
 148                                 return -EINVAL;
 149                 fasync_ok:
 150                         filp->f_owner = arg;
 151                         if (S_ISSOCK (filp->f_inode->i_mode))
 152                                 sock_fcntl (filp, F_SETOWN, arg);
 153                         return 0;
 154                 default:
 155                         /* sockets need a few special fcntls. */
 156                         if (S_ISSOCK (filp->f_inode->i_mode))
 157                           {
 158                              return (sock_fcntl (filp, cmd, arg));
 159                           }
 160                         return -EINVAL;
 161         }
 162 }
 163 
 164 void kill_fasync(struct fasync_struct *fa, int sig)
     /*  */
 165 {
 166         while (fa) {
 167                 if (fa->magic != FASYNC_MAGIC) {
 168                         printk("kill_fasync: bad magic number in "
 169                                "fasync_struct!\n");
 170                         return;
 171                 }
 172                 if (fa->fa_file->f_owner > 0)
 173                         kill_proc(fa->fa_file->f_owner, sig, 1);
 174                 else
 175                         kill_pg(-fa->fa_file->f_owner, sig, 1);
 176                 fa = fa->fa_next;
 177         }
 178 }
/* */
root/fs/fcntl.c

DEFINITIONS
