ipc/shm.c

   1 /*
   2  * linux/ipc/shm.c
   3  * Copyright (C) 1992, 1993 Krishna Balasubramanian
   4  *       Many improvements/fixes by Bruno Haible.
   5  * Replaced `struct shm_desc' by `struct vm_area_struct', July 1994.
   6  * Fixed the shm swap deallocation (shm_unuse()), August 1998 Andrea Arcangeli.
   7  *
   8  * /proc/sysvipc/shm support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
   9  * BIGMEM support, Andrea Arcangeli <andrea@suse.de>
  10  * SMP thread shm, Jean-Luc Boyard <jean-luc.boyard@siemens.fr>
  11  * HIGHMEM support, Ingo Molnar <mingo@redhat.com>
  12  * Make shmmax, shmall, shmmni sysctl'able, Christoph Rohland <cr@sap.com>
  13  * Shared /dev/zero support, Kanoj Sarcar <kanoj@sgi.com>
  14  * Move the mm functionality over to mm/shmem.c, Christoph Rohland <cr@sap.com>
  15  *
  16  */
  17
  18 #include <linux/config.h>
  19 #include <linux/slab.h>
  20 #include <linux/mm.h>
  21 #include <linux/hugetlb.h>
  22 #include <linux/shm.h>
  23 #include <linux/init.h>
  24 #include <linux/file.h>
  25 #include <linux/mman.h>
  26 #include <linux/shmem_fs.h>
  27 #include <linux/security.h>
  28 #include <linux/syscalls.h>
  29 #include <linux/audit.h>
  30 #include <linux/capability.h>
  31 #include <linux/ptrace.h>
  32 #include <linux/seq_file.h>
  33
  34 #include <asm/uaccess.h>
  35
  36 #include "util.h"
  37
  38 static struct file_operations shm_file_operations;
  39 static struct vm_operations_struct shm_vm_ops;
  40
  41 static struct ipc_ids shm_ids;
  42
  43 #define shm_lock(id)    ((struct shmid_kernel*)ipc_lock(&shm_ids,id))
  44 #define shm_unlock(shp) ipc_unlock(&(shp)->shm_perm)
  45 #define shm_get(id)     ((struct shmid_kernel*)ipc_get(&shm_ids,id))
  46 #define shm_buildid(id, seq) \
  47         ipc_buildid(&shm_ids, id, seq)
  48
  49 static int newseg (key_t key, int shmflg, size_t size);
  50 static void shm_open (struct vm_area_struct *shmd);
  51 static void shm_close (struct vm_area_struct *shmd);
  52 #ifdef CONFIG_PROC_FS
  53 static int sysvipc_shm_proc_show(struct seq_file *s, void *it);
  54 #endif
  55
  56 size_t  shm_ctlmax = SHMMAX;
  57 size_t  shm_ctlall = SHMALL;
  58 int     shm_ctlmni = SHMMNI;
  59
  60 static int shm_tot; /* total number of shared memory pages */
  61
  62 void __init shm_init (void)
  63 {
  64         ipc_init_ids(&shm_ids, 1);
  65         ipc_init_proc_interface("sysvipc/shm",
  66                                 "       key      shmid perms       size  cpid  lpid nattch   uid   gid  cuid  cgid      atime      dtime      ctime\n",
  67                                 &shm_ids,
  68                                 sysvipc_shm_proc_show);
  69 }
  70
  71 static inline int shm_checkid(struct shmid_kernel *s, int id)
  72 {
  73         if (ipc_checkid(&shm_ids,&s->shm_perm,id))
  74                 return -EIDRM;
  75         return 0;
  76 }
  77
  78 static inline struct shmid_kernel *shm_rmid(int id)
  79 {
  80         return (struct shmid_kernel *)ipc_rmid(&shm_ids,id);
  81 }
  82
  83 static inline int shm_addid(struct shmid_kernel *shp)
  84 {
  85         return ipc_addid(&shm_ids, &shp->shm_perm, shm_ctlmni);
  86 }
  87
  88
  89
  90 static inline void shm_inc (int id) {
  91         struct shmid_kernel *shp;
  92
  93         if(!(shp = shm_lock(id)))
  94                 BUG();
  95         shp->shm_atim = get_seconds();
  96         shp->shm_lprid = current->tgid;
  97         shp->shm_nattch++;
  98         shm_unlock(shp);
  99 }
 100
 101 /* This is called by fork, once for every shm attach. */
 102 static void shm_open (struct vm_area_struct *shmd)
 103 {
 104         shm_inc (shmd->vm_file->f_dentry->d_inode->i_ino);
 105 }
 106
 107 /*
 108  * shm_destroy - free the struct shmid_kernel
 109  *
 110  * @shp: struct to free
 111  *
 112  * It has to be called with shp and shm_ids.sem locked,
 113  * but returns with shp unlocked and freed.
 114  */
 115 static void shm_destroy (struct shmid_kernel *shp)
 116 {
 117         shm_tot -= (shp->shm_segsz + PAGE_SIZE - 1) >> PAGE_SHIFT;
 118         shm_rmid (shp->id);
 119         shm_unlock(shp);
 120         if (!is_file_hugepages(shp->shm_file))
 121                 shmem_lock(shp->shm_file, 0, shp->mlock_user);
 122         else
 123                 user_shm_unlock(shp->shm_file->f_dentry->d_inode->i_size,
 124                                                 shp->mlock_user);
 125         fput (shp->shm_file);
 126         security_shm_free(shp);
 127         ipc_rcu_putref(shp);
 128 }
 129
 130 /*
 131  * remove the attach descriptor shmd.
 132  * free memory for segment if it is marked destroyed.
 133  * The descriptor has already been removed from the current->mm->mmap list
 134  * and will later be kfree()d.
 135  */
 136 static void shm_close (struct vm_area_struct *shmd)
 137 {
 138         struct file * file = shmd->vm_file;
 139         int id = file->f_dentry->d_inode->i_ino;
 140         struct shmid_kernel *shp;
 141
 142         down (&shm_ids.sem);
 143         /* remove from the list of attaches of the shm segment */
 144         if(!(shp = shm_lock(id)))
 145                 BUG();
 146         shp->shm_lprid = current->tgid;
 147         shp->shm_dtim = get_seconds();
 148         shp->shm_nattch--;
 149         if(shp->shm_nattch == 0 &&
 150            shp->shm_perm.mode & SHM_DEST)
 151                 shm_destroy (shp);
 152         else
 153                 shm_unlock(shp);
 154         up (&shm_ids.sem);
 155 }
 156
 157 static int shm_mmap(struct file * file, struct vm_area_struct * vma)
 158 {
 159         int ret;
 160
 161         ret = shmem_mmap(file, vma);
 162         if (ret == 0) {
 163                 vma->vm_ops = &shm_vm_ops;
 164                 shm_inc(file->f_dentry->d_inode->i_ino);
 165         }
 166
 167         return ret;
 168 }
 169
 170 static struct file_operations shm_file_operations = {
 171         .mmap   = shm_mmap,
 172 #ifndef CONFIG_MMU
 173         .get_unmapped_area = shmem_get_unmapped_area,
 174 #endif
 175 };
 176
 177 static struct vm_operations_struct shm_vm_ops = {
 178         .open   = shm_open,     /* callback for a new vm-area open */
 179         .close  = shm_close,    /* callback for when the vm-area is released */
 180         .nopage = shmem_nopage,
 181 #if defined(CONFIG_NUMA) && defined(CONFIG_SHMEM)
 182         .set_policy = shmem_set_policy,
 183         .get_policy = shmem_get_policy,
 184 #endif
 185 };
 186
 187 static int newseg (key_t key, int shmflg, size_t size)
 188 {
 189         int error;
 190         struct shmid_kernel *shp;
 191         int numpages = (size + PAGE_SIZE -1) >> PAGE_SHIFT;
 192         struct file * file;
 193         char name[13];
 194         int id;
 195
 196         if (size < SHMMIN || size > shm_ctlmax)
 197                 return -EINVAL;
 198
 199         if (shm_tot + numpages >= shm_ctlall)
 200                 return -ENOSPC;
 201
 202         shp = ipc_rcu_alloc(sizeof(*shp));
 203         if (!shp)
 204                 return -ENOMEM;
 205
 206         shp->shm_perm.key = key;
 207         shp->shm_perm.mode = (shmflg & S_IRWXUGO);
 208         shp->mlock_user = NULL;
 209
 210         shp->shm_perm.security = NULL;
 211         error = security_shm_alloc(shp);
 212         if (error) {
 213                 ipc_rcu_putref(shp);
 214                 return error;
 215         }
 216
 217         if (shmflg & SHM_HUGETLB) {
 218                 /* hugetlb_zero_setup takes care of mlock user accounting */
 219                 file = hugetlb_zero_setup(size);
 220                 shp->mlock_user = current->user;
 221         } else {
 222                 int acctflag = VM_ACCOUNT;
 223                 /*
 224                  * Do not allow no accounting for OVERCOMMIT_NEVER, even
 225                  * if it's asked for.
 226                  */
 227                 if  ((shmflg & SHM_NORESERVE) &&
 228                                 sysctl_overcommit_memory != OVERCOMMIT_NEVER)
 229                         acctflag = 0;
 230                 sprintf (name, "SYSV%08x", key);
 231                 file = shmem_file_setup(name, size, acctflag);
 232         }
 233         error = PTR_ERR(file);
 234         if (IS_ERR(file))
 235                 goto no_file;
 236
 237         error = -ENOSPC;
 238         id = shm_addid(shp);
 239         if(id == -1)
 240                 goto no_id;
 241
 242         shp->shm_cprid = current->tgid;
 243         shp->shm_lprid = 0;
 244         shp->shm_atim = shp->shm_dtim = 0;
 245         shp->shm_ctim = get_seconds();
 246         shp->shm_segsz = size;
 247         shp->shm_nattch = 0;
 248         shp->id = shm_buildid(id,shp->shm_perm.seq);
 249         shp->shm_file = file;
 250         file->f_dentry->d_inode->i_ino = shp->id;
 251
 252         /* Hugetlb ops would have already been assigned. */
 253         if (!(shmflg & SHM_HUGETLB))
 254                 file->f_op = &shm_file_operations;
 255
 256         shm_tot += numpages;
 257         shm_unlock(shp);
 258         return shp->id;
 259
 260 no_id:
 261         fput(file);
 262 no_file:
 263         security_shm_free(shp);
 264         ipc_rcu_putref(shp);
 265         return error;
 266 }
 267
 268 asmlinkage long sys_shmget (key_t key, size_t size, int shmflg)
 269 {
 270         struct shmid_kernel *shp;
 271         int err, id = 0;
 272
 273         down(&shm_ids.sem);
 274         if (key == IPC_PRIVATE) {
 275                 err = newseg(key, shmflg, size);
 276         } else if ((id = ipc_findkey(&shm_ids, key)) == -1) {
 277                 if (!(shmflg & IPC_CREAT))
 278                         err = -ENOENT;
 279                 else
 280                         err = newseg(key, shmflg, size);
 281         } else if ((shmflg & IPC_CREAT) && (shmflg & IPC_EXCL)) {
 282                 err = -EEXIST;
 283         } else {
 284                 shp = shm_lock(id);
 285                 if(shp==NULL)
 286                         BUG();
 287                 if (shp->shm_segsz < size)
 288                         err = -EINVAL;
 289                 else if (ipcperms(&shp->shm_perm, shmflg))
 290                         err = -EACCES;
 291                 else {
 292                         int shmid = shm_buildid(id, shp->shm_perm.seq);
 293                         err = security_shm_associate(shp, shmflg);
 294                         if (!err)
 295                                 err = shmid;
 296                 }
 297                 shm_unlock(shp);
 298         }
 299         up(&shm_ids.sem);
 300
 301         return err;
 302 }
 303
 304 static inline unsigned long copy_shmid_to_user(void __user *buf, struct shmid64_ds *in, int version)
 305 {
 306         switch(version) {
 307         case IPC_64:
 308                 return copy_to_user(buf, in, sizeof(*in));
 309         case IPC_OLD:
 310             {
 311                 struct shmid_ds out;
 312
 313                 ipc64_perm_to_ipc_perm(&in->shm_perm, &out.shm_perm);
 314                 out.shm_segsz   = in->shm_segsz;
 315                 out.shm_atime   = in->shm_atime;
 316                 out.shm_dtime   = in->shm_dtime;
 317                 out.shm_ctime   = in->shm_ctime;
 318                 out.shm_cpid    = in->shm_cpid;
 319                 out.shm_lpid    = in->shm_lpid;
 320                 out.shm_nattch  = in->shm_nattch;
 321
 322                 return copy_to_user(buf, &out, sizeof(out));
 323             }
 324         default:
 325                 return -EINVAL;
 326         }
 327 }
 328
 329 struct shm_setbuf {
 330         uid_t   uid;
 331         gid_t   gid;
 332         mode_t  mode;
 333 };
 334
 335 static inline unsigned long copy_shmid_from_user(struct shm_setbuf *out, void __user *buf, int version)
 336 {
 337         switch(version) {
 338         case IPC_64:
 339             {
 340                 struct shmid64_ds tbuf;
 341
 342                 if (copy_from_user(&tbuf, buf, sizeof(tbuf)))
 343                         return -EFAULT;
 344
 345                 out->uid        = tbuf.shm_perm.uid;
 346                 out->gid        = tbuf.shm_perm.gid;
 347                 out->mode       = tbuf.shm_perm.mode;
 348
 349                 return 0;
 350             }
 351         case IPC_OLD:
 352             {
 353                 struct shmid_ds tbuf_old;
 354
 355                 if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
 356                         return -EFAULT;
 357
 358                 out->uid        = tbuf_old.shm_perm.uid;
 359                 out->gid        = tbuf_old.shm_perm.gid;
 360                 out->mode       = tbuf_old.shm_perm.mode;
 361
 362                 return 0;
 363             }
 364         default:
 365                 return -EINVAL;
 366         }
 367 }
 368
 369 static inline unsigned long copy_shminfo_to_user(void __user *buf, struct shminfo64 *in, int version)
 370 {
 371         switch(version) {
 372         case IPC_64:
 373                 return copy_to_user(buf, in, sizeof(*in));
 374         case IPC_OLD:
 375             {
 376                 struct shminfo out;
 377
 378                 if(in->shmmax > INT_MAX)
 379                         out.shmmax = INT_MAX;
 380                 else
 381                         out.shmmax = (int)in->shmmax;
 382
 383                 out.shmmin      = in->shmmin;
 384                 out.shmmni      = in->shmmni;
 385                 out.shmseg      = in->shmseg;
 386                 out.shmall      = in->shmall;
 387
 388                 return copy_to_user(buf, &out, sizeof(out));
 389             }
 390         default:
 391                 return -EINVAL;
 392         }
 393 }
 394
 395 static void shm_get_stat(unsigned long *rss, unsigned long *swp)
 396 {
 397         int i;
 398
 399         *rss = 0;
 400         *swp = 0;
 401
 402         for (i = 0; i <= shm_ids.max_id; i++) {
 403                 struct shmid_kernel *shp;
 404                 struct inode *inode;
 405
 406                 shp = shm_get(i);
 407                 if(!shp)
 408                         continue;
 409
 410                 inode = shp->shm_file->f_dentry->d_inode;
 411
 412                 if (is_file_hugepages(shp->shm_file)) {
 413                         struct address_space *mapping = inode->i_mapping;
 414                         *rss += (HPAGE_SIZE/PAGE_SIZE)*mapping->nrpages;
 415                 } else {
 416                         struct shmem_inode_info *info = SHMEM_I(inode);
 417                         spin_lock(&info->lock);
 418                         *rss += inode->i_mapping->nrpages;
 419                         *swp += info->swapped;
 420                         spin_unlock(&info->lock);
 421                 }
 422         }
 423 }
 424
 425 asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds __user *buf)
 426 {
 427         struct shm_setbuf setbuf;
 428         struct shmid_kernel *shp;
 429         int err, version;
 430
 431         if (cmd < 0 || shmid < 0) {
 432                 err = -EINVAL;
 433                 goto out;
 434         }
 435
 436         version = ipc_parse_version(&cmd);
 437
 438         switch (cmd) { /* replace with proc interface ? */
 439         case IPC_INFO:
 440         {
 441                 struct shminfo64 shminfo;
 442
 443                 err = security_shm_shmctl(NULL, cmd);
 444                 if (err)
 445                         return err;
 446
 447                 memset(&shminfo,0,sizeof(shminfo));
 448                 shminfo.shmmni = shminfo.shmseg = shm_ctlmni;
 449                 shminfo.shmmax = shm_ctlmax;
 450                 shminfo.shmall = shm_ctlall;
 451
 452                 shminfo.shmmin = SHMMIN;
 453                 if(copy_shminfo_to_user (buf, &shminfo, version))
 454                         return -EFAULT;
 455                 /* reading a integer is always atomic */
 456                 err= shm_ids.max_id;
 457                 if(err<0)
 458                         err = 0;
 459                 goto out;
 460         }
 461         case SHM_INFO:
 462         {
 463                 struct shm_info shm_info;
 464
 465                 err = security_shm_shmctl(NULL, cmd);
 466                 if (err)
 467                         return err;
 468
 469                 memset(&shm_info,0,sizeof(shm_info));
 470                 down(&shm_ids.sem);
 471                 shm_info.used_ids = shm_ids.in_use;
 472                 shm_get_stat (&shm_info.shm_rss, &shm_info.shm_swp);
 473                 shm_info.shm_tot = shm_tot;
 474                 shm_info.swap_attempts = 0;
 475                 shm_info.swap_successes = 0;
 476                 err = shm_ids.max_id;
 477                 up(&shm_ids.sem);
 478                 if(copy_to_user (buf, &shm_info, sizeof(shm_info))) {
 479                         err = -EFAULT;
 480                         goto out;
 481                 }
 482
 483                 err = err < 0 ? 0 : err;
 484                 goto out;
 485         }
 486         case SHM_STAT:
 487         case IPC_STAT:
 488         {
 489                 struct shmid64_ds tbuf;
 490                 int result;
 491                 memset(&tbuf, 0, sizeof(tbuf));
 492                 shp = shm_lock(shmid);
 493                 if(shp==NULL) {
 494                         err = -EINVAL;
 495                         goto out;
 496                 } else if(cmd==SHM_STAT) {
 497                         err = -EINVAL;
 498                         if (shmid > shm_ids.max_id)
 499                                 goto out_unlock;
 500                         result = shm_buildid(shmid, shp->shm_perm.seq);
 501                 } else {
 502                         err = shm_checkid(shp,shmid);
 503                         if(err)
 504                                 goto out_unlock;
 505                         result = 0;
 506                 }
 507                 err=-EACCES;
 508                 if (ipcperms (&shp->shm_perm, S_IRUGO))
 509                         goto out_unlock;
 510                 err = security_shm_shmctl(shp, cmd);
 511                 if (err)
 512                         goto out_unlock;
 513                 kernel_to_ipc64_perm(&shp->shm_perm, &tbuf.shm_perm);
 514                 tbuf.shm_segsz  = shp->shm_segsz;
 515                 tbuf.shm_atime  = shp->shm_atim;
 516                 tbuf.shm_dtime  = shp->shm_dtim;
 517                 tbuf.shm_ctime  = shp->shm_ctim;
 518                 tbuf.shm_cpid   = shp->shm_cprid;
 519                 tbuf.shm_lpid   = shp->shm_lprid;
 520                 if (!is_file_hugepages(shp->shm_file))
 521                         tbuf.shm_nattch = shp->shm_nattch;
 522                 else
 523                         tbuf.shm_nattch = file_count(shp->shm_file) - 1;
 524                 shm_unlock(shp);
 525                 if(copy_shmid_to_user (buf, &tbuf, version))
 526                         err = -EFAULT;
 527                 else
 528                         err = result;
 529                 goto out;
 530         }
 531         case SHM_LOCK:
 532         case SHM_UNLOCK:
 533         {
 534                 shp = shm_lock(shmid);
 535                 if(shp==NULL) {
 536                         err = -EINVAL;
 537                         goto out;
 538                 }
 539                 err = shm_checkid(shp,shmid);
 540                 if(err)
 541                         goto out_unlock;
 542
 543                 if (!capable(CAP_IPC_LOCK)) {
 544                         err = -EPERM;
 545                         if (current->euid != shp->shm_perm.uid &&
 546                             current->euid != shp->shm_perm.cuid)
 547                                 goto out_unlock;
 548                         if (cmd == SHM_LOCK &&
 549                             !current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur)
 550                                 goto out_unlock;
 551                 }
 552
 553                 err = security_shm_shmctl(shp, cmd);
 554                 if (err)
 555                         goto out_unlock;
 556
 557                 if(cmd==SHM_LOCK) {
 558                         struct user_struct * user = current->user;
 559                         if (!is_file_hugepages(shp->shm_file)) {
 560                                 err = shmem_lock(shp->shm_file, 1, user);
 561                                 if (!err) {
 562                                         shp->shm_perm.mode |= SHM_LOCKED;
 563                                         shp->mlock_user = user;
 564                                 }
 565                         }
 566                 } else if (!is_file_hugepages(shp->shm_file)) {
 567                         shmem_lock(shp->shm_file, 0, shp->mlock_user);
 568                         shp->shm_perm.mode &= ~SHM_LOCKED;
 569                         shp->mlock_user = NULL;
 570                 }
 571                 shm_unlock(shp);
 572                 goto out;
 573         }
 574         case IPC_RMID:
 575         {
 576                 /*
 577                  *      We cannot simply remove the file. The SVID states
 578                  *      that the block remains until the last person
 579                  *      detaches from it, then is deleted. A shmat() on
 580                  *      an RMID segment is legal in older Linux and if
 581                  *      we change it apps break...
 582                  *
 583                  *      Instead we set a destroyed flag, and then blow
 584                  *      the name away when the usage hits zero.
 585                  */
 586                 down(&shm_ids.sem);
 587                 shp = shm_lock(shmid);
 588                 err = -EINVAL;
 589                 if (shp == NULL)
 590                         goto out_up;
 591                 err = shm_checkid(shp, shmid);
 592                 if(err)
 593                         goto out_unlock_up;
 594
 595                 if (current->euid != shp->shm_perm.uid &&
 596                     current->euid != shp->shm_perm.cuid &&
 597                     !capable(CAP_SYS_ADMIN)) {
 598                         err=-EPERM;
 599                         goto out_unlock_up;
 600                 }
 601
 602                 err = security_shm_shmctl(shp, cmd);
 603                 if (err)
 604                         goto out_unlock_up;
 605
 606                 if (shp->shm_nattch){
 607                         shp->shm_perm.mode |= SHM_DEST;
 608                         /* Do not find it any more */
 609                         shp->shm_perm.key = IPC_PRIVATE;
 610                         shm_unlock(shp);
 611                 } else
 612                         shm_destroy (shp);
 613                 up(&shm_ids.sem);
 614                 goto out;
 615         }
 616
 617         case IPC_SET:
 618         {
 619                 if (copy_shmid_from_user (&setbuf, buf, version)) {
 620                         err = -EFAULT;
 621                         goto out;
 622                 }
 623                 if ((err = audit_ipc_perms(0, setbuf.uid, setbuf.gid, setbuf.mode)))
 624                         return err;
 625                 down(&shm_ids.sem);
 626                 shp = shm_lock(shmid);
 627                 err=-EINVAL;
 628                 if(shp==NULL)
 629                         goto out_up;
 630                 err = shm_checkid(shp,shmid);
 631                 if(err)
 632                         goto out_unlock_up;
 633                 err=-EPERM;
 634                 if (current->euid != shp->shm_perm.uid &&
 635                     current->euid != shp->shm_perm.cuid &&
 636                     !capable(CAP_SYS_ADMIN)) {
 637                         goto out_unlock_up;
 638                 }
 639
 640                 err = security_shm_shmctl(shp, cmd);
 641                 if (err)
 642                         goto out_unlock_up;
 643
 644                 shp->shm_perm.uid = setbuf.uid;
 645                 shp->shm_perm.gid = setbuf.gid;
 646                 shp->shm_perm.mode = (shp->shm_perm.mode & ~S_IRWXUGO)
 647                         | (setbuf.mode & S_IRWXUGO);
 648                 shp->shm_ctim = get_seconds();
 649                 break;
 650         }
 651
 652         default:
 653                 err = -EINVAL;
 654                 goto out;
 655         }
 656
 657         err = 0;
 658 out_unlock_up:
 659         shm_unlock(shp);
 660 out_up:
 661         up(&shm_ids.sem);
 662         goto out;
 663 out_unlock:
 664         shm_unlock(shp);
 665 out:
 666         return err;
 667 }
 668
 669 /*
 670  * Fix shmaddr, allocate descriptor, map shm, add attach descriptor to lists.
 671  *
 672  * NOTE! Despite the name, this is NOT a direct system call entrypoint. The
 673  * "raddr" thing points to kernel space, and there has to be a wrapper around
 674  * this.
 675  */
 676 long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr)
 677 {
 678         struct shmid_kernel *shp;
 679         unsigned long addr;
 680         unsigned long size;
 681         struct file * file;
 682         int    err;
 683         unsigned long flags;
 684         unsigned long prot;
 685         unsigned long o_flags;
 686         int acc_mode;
 687         void *user_addr;
 688
 689         if (shmid < 0) {
 690                 err = -EINVAL;
 691                 goto out;
 692         } else if ((addr = (ulong)shmaddr)) {
 693                 if (addr & (SHMLBA-1)) {
 694                         if (shmflg & SHM_RND)
 695                                 addr &= ~(SHMLBA-1);       /* round down */
 696                         else
 697 #ifndef __ARCH_FORCE_SHMLBA
 698                                 if (addr & ~PAGE_MASK)
 699 #endif
 700                                         return -EINVAL;
 701                 }
 702                 flags = MAP_SHARED | MAP_FIXED;
 703         } else {
 704                 if ((shmflg & SHM_REMAP))
 705                         return -EINVAL;
 706
 707                 flags = MAP_SHARED;
 708         }
 709
 710         if (shmflg & SHM_RDONLY) {
 711                 prot = PROT_READ;
 712                 o_flags = O_RDONLY;
 713                 acc_mode = S_IRUGO;
 714         } else {
 715                 prot = PROT_READ | PROT_WRITE;
 716                 o_flags = O_RDWR;
 717                 acc_mode = S_IRUGO | S_IWUGO;
 718         }
 719         if (shmflg & SHM_EXEC) {
 720                 prot |= PROT_EXEC;
 721                 acc_mode |= S_IXUGO;
 722         }
 723
 724         /*
 725          * We cannot rely on the fs check since SYSV IPC does have an
 726          * additional creator id...
 727          */
 728         shp = shm_lock(shmid);
 729         if(shp == NULL) {
 730                 err = -EINVAL;
 731                 goto out;
 732         }
 733         err = shm_checkid(shp,shmid);
 734         if (err) {
 735                 shm_unlock(shp);
 736                 goto out;
 737         }
 738         if (ipcperms(&shp->shm_perm, acc_mode)) {
 739                 shm_unlock(shp);
 740                 err = -EACCES;
 741                 goto out;
 742         }
 743
 744         err = security_shm_shmat(shp, shmaddr, shmflg);
 745         if (err) {
 746                 shm_unlock(shp);
 747                 return err;
 748         }
 749
 750         file = shp->shm_file;
 751         size = i_size_read(file->f_dentry->d_inode);
 752         shp->shm_nattch++;
 753         shm_unlock(shp);
 754
 755         down_write(&current->mm->mmap_sem);
 756         if (addr && !(shmflg & SHM_REMAP)) {
 757                 user_addr = ERR_PTR(-EINVAL);
 758                 if (find_vma_intersection(current->mm, addr, addr + size))
 759                         goto invalid;
 760                 /*
 761                  * If shm segment goes below stack, make sure there is some
 762                  * space left for the stack to grow (at least 4 pages).
 763                  */
 764                 if (addr < current->mm->start_stack &&
 765                     addr > current->mm->start_stack - size - PAGE_SIZE * 5)
 766                         goto invalid;
 767         }
 768
 769         user_addr = (void*) do_mmap (file, addr, size, prot, flags, 0);
 770
 771 invalid:
 772         up_write(&current->mm->mmap_sem);
 773
 774         down (&shm_ids.sem);
 775         if(!(shp = shm_lock(shmid)))
 776                 BUG();
 777         shp->shm_nattch--;
 778         if(shp->shm_nattch == 0 &&
 779            shp->shm_perm.mode & SHM_DEST)
 780                 shm_destroy (shp);
 781         else
 782                 shm_unlock(shp);
 783         up (&shm_ids.sem);
 784
 785         *raddr = (unsigned long) user_addr;
 786         err = 0;
 787         if (IS_ERR(user_addr))
 788                 err = PTR_ERR(user_addr);
 789 out:
 790         return err;
 791 }
 792
 793 asmlinkage long sys_shmat(int shmid, char __user *shmaddr, int shmflg)
 794 {
 795         unsigned long ret;
 796         long err;
 797
 798         err = do_shmat(shmid, shmaddr, shmflg, &ret);
 799         if (err)
 800                 return err;
 801         force_successful_syscall_return();
 802         return (long)ret;
 803 }
 804
 805 /*
 806  * detach and kill segment if marked destroyed.
 807  * The work is done in shm_close.
 808  */
 809 asmlinkage long sys_shmdt(char __user *shmaddr)
 810 {
 811         struct mm_struct *mm = current->mm;
 812         struct vm_area_struct *vma, *next;
 813         unsigned long addr = (unsigned long)shmaddr;
 814         loff_t size = 0;
 815         int retval = -EINVAL;
 816
 817         down_write(&mm->mmap_sem);
 818
 819         /*
 820          * This function tries to be smart and unmap shm segments that
 821          * were modified by partial mlock or munmap calls:
 822          * - It first determines the size of the shm segment that should be
 823          *   unmapped: It searches for a vma that is backed by shm and that
 824          *   started at address shmaddr. It records it's size and then unmaps
 825          *   it.
 826          * - Then it unmaps all shm vmas that started at shmaddr and that
 827          *   are within the initially determined size.
 828          * Errors from do_munmap are ignored: the function only fails if
 829          * it's called with invalid parameters or if it's called to unmap
 830          * a part of a vma. Both calls in this function are for full vmas,
 831          * the parameters are directly copied from the vma itself and always
 832          * valid - therefore do_munmap cannot fail. (famous last words?)
 833          */
 834         /*
 835          * If it had been mremap()'d, the starting address would not
 836          * match the usual checks anyway. So assume all vma's are
 837          * above the starting address given.
 838          */
 839         vma = find_vma(mm, addr);
 840
 841         while (vma) {
 842                 next = vma->vm_next;
 843
 844                 /*
 845                  * Check if the starting address would match, i.e. it's
 846                  * a fragment created by mprotect() and/or munmap(), or it
 847                  * otherwise it starts at this address with no hassles.
 848                  */
 849                 if ((vma->vm_ops == &shm_vm_ops || is_vm_hugetlb_page(vma)) &&
 850                         (vma->vm_start - addr)/PAGE_SIZE == vma->vm_pgoff) {
 851
 852
 853                         size = vma->vm_file->f_dentry->d_inode->i_size;
 854                         do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start);
 855                         /*
 856                          * We discovered the size of the shm segment, so
 857                          * break out of here and fall through to the next
 858                          * loop that uses the size information to stop
 859                          * searching for matching vma's.
 860                          */
 861                         retval = 0;
 862                         vma = next;
 863                         break;
 864                 }
 865                 vma = next;
 866         }
 867
 868         /*
 869          * We need look no further than the maximum address a fragment
 870          * could possibly have landed at. Also cast things to loff_t to
 871          * prevent overflows and make comparisions vs. equal-width types.
 872          */
 873         while (vma && (loff_t)(vma->vm_end - addr) <= size) {
 874                 next = vma->vm_next;
 875
 876                 /* finding a matching vma now does not alter retval */
 877                 if ((vma->vm_ops == &shm_vm_ops || is_vm_hugetlb_page(vma)) &&
 878                         (vma->vm_start - addr)/PAGE_SIZE == vma->vm_pgoff)
 879
 880                         do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start);
 881                 vma = next;
 882         }
 883
 884         up_write(&mm->mmap_sem);
 885         return retval;
 886 }
 887
 888 #ifdef CONFIG_PROC_FS
 889 static int sysvipc_shm_proc_show(struct seq_file *s, void *it)
 890 {
 891         struct shmid_kernel *shp = it;
 892         char *format;
 893
 894 #define SMALL_STRING "%10d %10d  %4o %10u %5u %5u  %5d %5u %5u %5u %5u %10lu %10lu %10lu\n"
 895 #define BIG_STRING   "%10d %10d  %4o %21u %5u %5u  %5d %5u %5u %5u %5u %10lu %10lu %10lu\n"
 896
 897         if (sizeof(size_t) <= sizeof(int))
 898                 format = SMALL_STRING;
 899         else
 900                 format = BIG_STRING;
 901         return seq_printf(s, format,
 902                           shp->shm_perm.key,
 903                           shp->id,
 904                           shp->shm_perm.mode,
 905                           shp->shm_segsz,
 906                           shp->shm_cprid,
 907                           shp->shm_lprid,
 908                           is_file_hugepages(shp->shm_file) ? (file_count(shp->shm_file) - 1) : shp->shm_nattch,
 909                           shp->shm_perm.uid,
 910                           shp->shm_perm.gid,
 911                           shp->shm_perm.cuid,
 912                           shp->shm_perm.cgid,
 913                           shp->shm_atim,
 914                           shp->shm_dtim,
 915                           shp->shm_ctim);
 916 }
 917 #endif