/* * access.c -- the files with access control on open (v2.1) * */ #ifndef __KERNEL__#  define __KERNEL__#endif#ifndef MODULE#  define MODULE#endif#define __NO_VERSION__#include <linux/module.h> /* get MOD_DEC_USE_COUNT, not the version string */#include <linux/version.h> /* need it for conditionals in scull.h */#include <linux/kernel.h> /* printk() */#include <linux/malloc.h> /* kmalloc() */#include <linux/fs.h>     /* everything... */#include <linux/proc_fs.h>#include <linux/errno.h>  /* error codes */#include <linux/types.h>  /* size_t */#include <linux/fcntl.h>#include <linux/tty.h>    /* current->tty */#include "scull.h"        /* local definitions *//* * These devices fall back on the main scull operations. They only * differ in the implementation of open() and close() *//************************************************************************ * * The first device is the single-open one, *  it has an hw structure and an open count */ Scull_Dev scull_s_device; int scull_s_count = 0;int scull_s_open (struct inode *inode, struct file *filp){    Scull_Dev *dev = &scull_s_device; /* device information */    int num = NUM(inode->i_rdev);    if (num > 0) return -ENODEV; /* 1 device only */    if (scull_s_count) return -EBUSY; /* already open */    scull_s_count++;    /* then, everything else is copied from the bare scull device */    if ( (filp->f_flags & O_ACCMODE) == O_WRONLY)        scull_trim(dev);    filp->private_data = dev;    MOD_INC_USE_COUNT;    return 0;          /* success */}release_t scull_s_release (struct inode *inode, struct file *filp){    scull_s_count--; /* release the device */    MOD_DEC_USE_COUNT;    release_return(0);}/* * The other operations for the single-open device come from the bare device */struct file_operations scull_sngl_fops = {    scull_lseek,    scull_read,    scull_write,    NULL,          /* scull_readdir */    NULL,          /* scull_select */    scull_ioctl,    NULL,          /* scull_mmap */    scull_s_open,    scull_s_release,    NULL,          /* scull_fsync */    NULL,          /* scull_fasync */                   /* nothing more, fill with NULLs */};/************************************************************************ * * Next, the "uid" device. It can be opened multiple times by the * same user, but access is denied to other users if the device is open */Scull_Dev scull_u_device;int scull_u_count = 0;uid_t scull_u_owner = 0;int scull_u_open (struct inode *inode, struct file *filp){    Scull_Dev *dev = &scull_u_device; /* device information */    int num = NUM(inode->i_rdev);    if (num > 0) return -ENODEV; /* 1 device only */    if (scull_u_count &&         (scull_u_owner != current->uid) &&  /* allow user */        (scull_u_owner != current->euid) && /* allow whoever did su */        !suser()) /* still allow root */         return -EBUSY;   /* -EPERM would confuse the user */    if (scull_u_count == 0)        scull_u_owner = current->uid; /* grab it */    scull_u_count++;    /* then, everything else is copied from the bare scull device */    if ( (filp->f_flags & O_ACCMODE) == O_WRONLY)        scull_trim(dev);    filp->private_data = dev;    MOD_INC_USE_COUNT;    return 0;          /* success */}release_t scull_u_release (struct inode *inode, struct file *filp){    scull_u_count--; /* nothing else */    MOD_DEC_USE_COUNT;    release_return(0);}/* * The other operations for the device come from the bare device */struct file_operations scull_user_fops = {    scull_lseek,    scull_read,    scull_write,    NULL,          /* scull_readdir */    NULL,          /* scull_select */    scull_ioctl,    NULL,          /* scull_mmap */    scull_u_open,    scull_u_release,    NULL,          /* scull_fsync */    NULL,          /* scull_fasync */                   /* nothing more, fill with NULLs */};/************************************************************************ * * Next, the device with blocking-open based on uid */Scull_Dev scull_w_device;int scull_w_count = 0;uid_t scull_w_owner = 0;struct wait_queue *scull_w_wait;int scull_w_open (struct inode *inode, struct file *filp){    Scull_Dev *dev = &scull_w_device; /* device information */    int num = NUM(inode->i_rdev);    if (num > 0) return -ENODEV; /* 1 device only */    while (scull_w_count &&       (scull_w_owner != current->uid) &&  /* allow user */      (scull_w_owner != current->euid) && /* allow whoever did su */      !suser()) {        if (filp->f_flags & O_NONBLOCK) return -EAGAIN;         interruptible_sleep_on(&scull_w_wait);        if (current->signal & ~current->blocked) /* a signal arrived */          return -ERESTARTSYS; /* tell the fs layer to handle it */        /* else, loop */    }    if (scull_w_count == 0)        scull_w_owner = current->uid; /* grab it */    scull_w_count++;    /* then, everything else is copied from the bare scull device */    if ( (filp->f_flags & O_ACCMODE) == O_WRONLY)        scull_trim(dev);    filp->private_data = dev;    MOD_INC_USE_COUNT;    return 0;          /* success */}release_t scull_w_release (struct inode *inode, struct file *filp){    scull_w_count--;    if (scull_w_count == 0)        wake_up_interruptible(&scull_w_wait); /* awake other uid's */    MOD_DEC_USE_COUNT;    release_return(0);}/* * The other operations for the device come from the bare device */struct file_operations scull_wusr_fops = {    scull_lseek,    scull_read,    scull_write,    NULL,          /* scull_readdir */    NULL,          /* scull_select */    scull_ioctl,    NULL,          /* scull_mmap */    scull_w_open,    scull_w_release,    NULL,          /* scull_fsync */    NULL,          /* scull_fasync */                   /* nothing more, fill with NULLs */};/************************************************************************ * * Finally the `cloned' private device. This is trickier because it * involves list management, and dynamic allocation. */struct scull_listitem {    Scull_Dev device;    int key;    struct scull_listitem *next;};struct scull_listitem *scull_c_head;int scull_c_open (struct inode *inode, struct file *filp){    int key;    int num = NUM(inode->i_rdev);    struct scull_listitem *lptr, *prev;    if (num > 0) return -ENODEV; /* 1 device only */    if (!current->tty) {        PDEBUG("Process \"%s\" has no ctl tty\n",current->comm);        return -EINVAL;    }    key = MINOR(current->tty->device);    /* look for a device in the linked list; if missing create it */    prev = NULL;    for (lptr = scull_c_head; lptr && (lptr->key != key); lptr = lptr->next)        prev=lptr;    if (!lptr) { /* not found */        lptr = kmalloc(sizeof(struct scull_listitem), GFP_KERNEL);        if (!lptr)            return -ENOMEM;        memset(lptr, 0, sizeof(struct scull_listitem));        lptr->key = key;        scull_trim(&(lptr->device)); /* initialize it */        if (prev)            prev->next = lptr;        else            scull_c_head = lptr; /* the first one */    }    /* then, everything else is copied from the bare scull device */    if ( (filp->f_flags & O_ACCMODE) == O_WRONLY)        scull_trim(&(lptr->device));    filp->private_data = &(lptr->device);    MOD_INC_USE_COUNT;    return 0;          /* success */}release_t scull_c_release (struct inode *inode, struct file *filp){    /*     * Nothing to do, because the device is persistent.     * A `real' cloned device should be freed on last close     */    MOD_DEC_USE_COUNT;    release_return(0);}/* * The other operations for the device come from the bare device */struct file_operations scull_priv_fops = {    scull_lseek,    scull_read,    scull_write,    NULL,          /* scull_readdir */    NULL,          /* scull_select */    scull_ioctl,    NULL,          /* scull_mmap */    scull_c_open,    scull_c_release,    NULL,          /* scull_fsync */    NULL,          /* scull_fasync */                   /* nothing more, fill with NULLs */};/************************************************************************ * * And the init and cleanup functions come last */int scull_access_init(void){    /* assign quantum and quantumset */    scull_s_device.quantum = scull_quantum;    scull_s_device.qset    = scull_qset;    scull_u_device.quantum = scull_quantum;    scull_u_device.qset    = scull_qset;    scull_w_device.quantum = scull_quantum;    scull_w_device.qset    = scull_qset;    return 0;}void scull_access_cleanup(void) /* called by cleanup_module */{    struct scull_listitem *lptr, *prev;    scull_trim(&scull_s_device); /* disallocate it */    scull_trim(&scull_u_device); /* disallocate it */    scull_trim(&scull_w_device); /* disallocate it */    /* all the cloned devices */    prev=NULL;    for (lptr = scull_c_head; lptr; lptr = lptr->next) {        scull_trim(&(lptr->device));        if (prev) kfree(prev);        prev=lptr;    }    if (prev) kfree(prev);    scull_c_head = NULL; /* overkill: we're unloading anyways */    return;}