linux/fs/fuse/ioctl.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * Copyright (C) 2017 Red Hat, Inc.
   4 */
   5
   6#include "fuse_i.h"
   7
   8#include <linux/uio.h>
   9#include <linux/compat.h>
  10#include <linux/fileattr.h>
  11
  12/*
  13 * CUSE servers compiled on 32bit broke on 64bit kernels because the
  14 * ABI was defined to be 'struct iovec' which is different on 32bit
  15 * and 64bit.  Fortunately we can determine which structure the server
  16 * used from the size of the reply.
  17 */
  18static int fuse_copy_ioctl_iovec_old(struct iovec *dst, void *src,
  19                                     size_t transferred, unsigned count,
  20                                     bool is_compat)
  21{
  22#ifdef CONFIG_COMPAT
  23        if (count * sizeof(struct compat_iovec) == transferred) {
  24                struct compat_iovec *ciov = src;
  25                unsigned i;
  26
  27                /*
  28                 * With this interface a 32bit server cannot support
  29                 * non-compat (i.e. ones coming from 64bit apps) ioctl
  30                 * requests
  31                 */
  32                if (!is_compat)
  33                        return -EINVAL;
  34
  35                for (i = 0; i < count; i++) {
  36                        dst[i].iov_base = compat_ptr(ciov[i].iov_base);
  37                        dst[i].iov_len = ciov[i].iov_len;
  38                }
  39                return 0;
  40        }
  41#endif
  42
  43        if (count * sizeof(struct iovec) != transferred)
  44                return -EIO;
  45
  46        memcpy(dst, src, transferred);
  47        return 0;
  48}
  49
  50/* Make sure iov_length() won't overflow */
  51static int fuse_verify_ioctl_iov(struct fuse_conn *fc, struct iovec *iov,
  52                                 size_t count)
  53{
  54        size_t n;
  55        u32 max = fc->max_pages << PAGE_SHIFT;
  56
  57        for (n = 0; n < count; n++, iov++) {
  58                if (iov->iov_len > (size_t) max)
  59                        return -ENOMEM;
  60                max -= iov->iov_len;
  61        }
  62        return 0;
  63}
  64
  65static int fuse_copy_ioctl_iovec(struct fuse_conn *fc, struct iovec *dst,
  66                                 void *src, size_t transferred, unsigned count,
  67                                 bool is_compat)
  68{
  69        unsigned i;
  70        struct fuse_ioctl_iovec *fiov = src;
  71
  72        if (fc->minor < 16) {
  73                return fuse_copy_ioctl_iovec_old(dst, src, transferred,
  74                                                 count, is_compat);
  75        }
  76
  77        if (count * sizeof(struct fuse_ioctl_iovec) != transferred)
  78                return -EIO;
  79
  80        for (i = 0; i < count; i++) {
  81                /* Did the server supply an inappropriate value? */
  82                if (fiov[i].base != (unsigned long) fiov[i].base ||
  83                    fiov[i].len != (unsigned long) fiov[i].len)
  84                        return -EIO;
  85
  86                dst[i].iov_base = (void __user *) (unsigned long) fiov[i].base;
  87                dst[i].iov_len = (size_t) fiov[i].len;
  88
  89#ifdef CONFIG_COMPAT
  90                if (is_compat &&
  91                    (ptr_to_compat(dst[i].iov_base) != fiov[i].base ||
  92                     (compat_size_t) dst[i].iov_len != fiov[i].len))
  93                        return -EIO;
  94#endif
  95        }
  96
  97        return 0;
  98}
  99
 100
 101/*
 102 * For ioctls, there is no generic way to determine how much memory
 103 * needs to be read and/or written.  Furthermore, ioctls are allowed
 104 * to dereference the passed pointer, so the parameter requires deep
 105 * copying but FUSE has no idea whatsoever about what to copy in or
 106 * out.
 107 *
 108 * This is solved by allowing FUSE server to retry ioctl with
 109 * necessary in/out iovecs.  Let's assume the ioctl implementation
 110 * needs to read in the following structure.
 111 *
 112 * struct a {
 113 *      char    *buf;
 114 *      size_t  buflen;
 115 * }
 116 *
 117 * On the first callout to FUSE server, inarg->in_size and
 118 * inarg->out_size will be NULL; then, the server completes the ioctl
 119 * with FUSE_IOCTL_RETRY set in out->flags, out->in_iovs set to 1 and
 120 * the actual iov array to
 121 *
 122 * { { .iov_base = inarg.arg,   .iov_len = sizeof(struct a) } }
 123 *
 124 * which tells FUSE to copy in the requested area and retry the ioctl.
 125 * On the second round, the server has access to the structure and
 126 * from that it can tell what to look for next, so on the invocation,
 127 * it sets FUSE_IOCTL_RETRY, out->in_iovs to 2 and iov array to
 128 *
 129 * { { .iov_base = inarg.arg,   .iov_len = sizeof(struct a)     },
 130 *   { .iov_base = a.buf,       .iov_len = a.buflen             } }
 131 *
 132 * FUSE will copy both struct a and the pointed buffer from the
 133 * process doing the ioctl and retry ioctl with both struct a and the
 134 * buffer.
 135 *
 136 * This time, FUSE server has everything it needs and completes ioctl
 137 * without FUSE_IOCTL_RETRY which finishes the ioctl call.
 138 *
 139 * Copying data out works the same way.
 140 *
 141 * Note that if FUSE_IOCTL_UNRESTRICTED is clear, the kernel
 142 * automatically initializes in and out iovs by decoding @cmd with
 143 * _IOC_* macros and the server is not allowed to request RETRY.  This
 144 * limits ioctl data transfers to well-formed ioctls and is the forced
 145 * behavior for all FUSE servers.
 146 */
 147long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
 148                   unsigned int flags)
 149{
 150        struct fuse_file *ff = file->private_data;
 151        struct fuse_mount *fm = ff->fm;
 152        struct fuse_ioctl_in inarg = {
 153                .fh = ff->fh,
 154                .cmd = cmd,
 155                .arg = arg,
 156                .flags = flags
 157        };
 158        struct fuse_ioctl_out outarg;
 159        struct iovec *iov_page = NULL;
 160        struct iovec *in_iov = NULL, *out_iov = NULL;
 161        unsigned int in_iovs = 0, out_iovs = 0, max_pages;
 162        size_t in_size, out_size, c;
 163        ssize_t transferred;
 164        int err, i;
 165        struct iov_iter ii;
 166        struct fuse_args_pages ap = {};
 167
 168#if BITS_PER_LONG == 32
 169        inarg.flags |= FUSE_IOCTL_32BIT;
 170#else
 171        if (flags & FUSE_IOCTL_COMPAT) {
 172                inarg.flags |= FUSE_IOCTL_32BIT;
 173#ifdef CONFIG_X86_X32
 174                if (in_x32_syscall())
 175                        inarg.flags |= FUSE_IOCTL_COMPAT_X32;
 176#endif
 177        }
 178#endif
 179
 180        /* assume all the iovs returned by client always fits in a page */
 181        BUILD_BUG_ON(sizeof(struct fuse_ioctl_iovec) * FUSE_IOCTL_MAX_IOV > PAGE_SIZE);
 182
 183        err = -ENOMEM;
 184        ap.pages = fuse_pages_alloc(fm->fc->max_pages, GFP_KERNEL, &ap.descs);
 185        iov_page = (struct iovec *) __get_free_page(GFP_KERNEL);
 186        if (!ap.pages || !iov_page)
 187                goto out;
 188
 189        fuse_page_descs_length_init(ap.descs, 0, fm->fc->max_pages);
 190
 191        /*
 192         * If restricted, initialize IO parameters as encoded in @cmd.
 193         * RETRY from server is not allowed.
 194         */
 195        if (!(flags & FUSE_IOCTL_UNRESTRICTED)) {
 196                struct iovec *iov = iov_page;
 197
 198                iov->iov_base = (void __user *)arg;
 199                iov->iov_len = _IOC_SIZE(cmd);
 200
 201                if (_IOC_DIR(cmd) & _IOC_WRITE) {
 202                        in_iov = iov;
 203                        in_iovs = 1;
 204                }
 205
 206                if (_IOC_DIR(cmd) & _IOC_READ) {
 207                        out_iov = iov;
 208                        out_iovs = 1;
 209                }
 210        }
 211
 212 retry:
 213        inarg.in_size = in_size = iov_length(in_iov, in_iovs);
 214        inarg.out_size = out_size = iov_length(out_iov, out_iovs);
 215
 216        /*
 217         * Out data can be used either for actual out data or iovs,
 218         * make sure there always is at least one page.
 219         */
 220        out_size = max_t(size_t, out_size, PAGE_SIZE);
 221        max_pages = DIV_ROUND_UP(max(in_size, out_size), PAGE_SIZE);
 222
 223        /* make sure there are enough buffer pages and init request with them */
 224        err = -ENOMEM;
 225        if (max_pages > fm->fc->max_pages)
 226                goto out;
 227        while (ap.num_pages < max_pages) {
 228                ap.pages[ap.num_pages] = alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
 229                if (!ap.pages[ap.num_pages])
 230                        goto out;
 231                ap.num_pages++;
 232        }
 233
 234
 235        /* okay, let's send it to the client */
 236        ap.args.opcode = FUSE_IOCTL;
 237        ap.args.nodeid = ff->nodeid;
 238        ap.args.in_numargs = 1;
 239        ap.args.in_args[0].size = sizeof(inarg);
 240        ap.args.in_args[0].value = &inarg;
 241        if (in_size) {
 242                ap.args.in_numargs++;
 243                ap.args.in_args[1].size = in_size;
 244                ap.args.in_pages = true;
 245
 246                err = -EFAULT;
 247                iov_iter_init(&ii, WRITE, in_iov, in_iovs, in_size);
 248                for (i = 0; iov_iter_count(&ii) && !WARN_ON(i >= ap.num_pages); i++) {
 249                        c = copy_page_from_iter(ap.pages[i], 0, PAGE_SIZE, &ii);
 250                        if (c != PAGE_SIZE && iov_iter_count(&ii))
 251                                goto out;
 252                }
 253        }
 254
 255        ap.args.out_numargs = 2;
 256        ap.args.out_args[0].size = sizeof(outarg);
 257        ap.args.out_args[0].value = &outarg;
 258        ap.args.out_args[1].size = out_size;
 259        ap.args.out_pages = true;
 260        ap.args.out_argvar = true;
 261
 262        transferred = fuse_simple_request(fm, &ap.args);
 263        err = transferred;
 264        if (transferred < 0)
 265                goto out;
 266
 267        /* did it ask for retry? */
 268        if (outarg.flags & FUSE_IOCTL_RETRY) {
 269                void *vaddr;
 270
 271                /* no retry if in restricted mode */
 272                err = -EIO;
 273                if (!(flags & FUSE_IOCTL_UNRESTRICTED))
 274                        goto out;
 275
 276                in_iovs = outarg.in_iovs;
 277                out_iovs = outarg.out_iovs;
 278
 279                /*
 280                 * Make sure things are in boundary, separate checks
 281                 * are to protect against overflow.
 282                 */
 283                err = -ENOMEM;
 284                if (in_iovs > FUSE_IOCTL_MAX_IOV ||
 285                    out_iovs > FUSE_IOCTL_MAX_IOV ||
 286                    in_iovs + out_iovs > FUSE_IOCTL_MAX_IOV)
 287                        goto out;
 288
 289                vaddr = kmap_atomic(ap.pages[0]);
 290                err = fuse_copy_ioctl_iovec(fm->fc, iov_page, vaddr,
 291                                            transferred, in_iovs + out_iovs,
 292                                            (flags & FUSE_IOCTL_COMPAT) != 0);
 293                kunmap_atomic(vaddr);
 294                if (err)
 295                        goto out;
 296
 297                in_iov = iov_page;
 298                out_iov = in_iov + in_iovs;
 299
 300                err = fuse_verify_ioctl_iov(fm->fc, in_iov, in_iovs);
 301                if (err)
 302                        goto out;
 303
 304                err = fuse_verify_ioctl_iov(fm->fc, out_iov, out_iovs);
 305                if (err)
 306                        goto out;
 307
 308                goto retry;
 309        }
 310
 311        err = -EIO;
 312        if (transferred > inarg.out_size)
 313                goto out;
 314
 315        err = -EFAULT;
 316        iov_iter_init(&ii, READ, out_iov, out_iovs, transferred);
 317        for (i = 0; iov_iter_count(&ii) && !WARN_ON(i >= ap.num_pages); i++) {
 318                c = copy_page_to_iter(ap.pages[i], 0, PAGE_SIZE, &ii);
 319                if (c != PAGE_SIZE && iov_iter_count(&ii))
 320                        goto out;
 321        }
 322        err = 0;
 323 out:
 324        free_page((unsigned long) iov_page);
 325        while (ap.num_pages)
 326                __free_page(ap.pages[--ap.num_pages]);
 327        kfree(ap.pages);
 328
 329        return err ? err : outarg.result;
 330}
 331EXPORT_SYMBOL_GPL(fuse_do_ioctl);
 332
 333long fuse_ioctl_common(struct file *file, unsigned int cmd,
 334                       unsigned long arg, unsigned int flags)
 335{
 336        struct inode *inode = file_inode(file);
 337        struct fuse_conn *fc = get_fuse_conn(inode);
 338
 339        if (!fuse_allow_current_process(fc))
 340                return -EACCES;
 341
 342        if (fuse_is_bad(inode))
 343                return -EIO;
 344
 345        return fuse_do_ioctl(file, cmd, arg, flags);
 346}
 347
 348long fuse_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 349{
 350        return fuse_ioctl_common(file, cmd, arg, 0);
 351}
 352
 353long fuse_file_compat_ioctl(struct file *file, unsigned int cmd,
 354                            unsigned long arg)
 355{
 356        return fuse_ioctl_common(file, cmd, arg, FUSE_IOCTL_COMPAT);
 357}
 358
 359static int fuse_priv_ioctl(struct inode *inode, struct fuse_file *ff,
 360                           unsigned int cmd, void *ptr, size_t size)
 361{
 362        struct fuse_mount *fm = ff->fm;
 363        struct fuse_ioctl_in inarg;
 364        struct fuse_ioctl_out outarg;
 365        FUSE_ARGS(args);
 366        int err;
 367
 368        memset(&inarg, 0, sizeof(inarg));
 369        inarg.fh = ff->fh;
 370        inarg.cmd = cmd;
 371
 372#if BITS_PER_LONG == 32
 373        inarg.flags |= FUSE_IOCTL_32BIT;
 374#endif
 375        if (S_ISDIR(inode->i_mode))
 376                inarg.flags |= FUSE_IOCTL_DIR;
 377
 378        if (_IOC_DIR(cmd) & _IOC_READ)
 379                inarg.out_size = size;
 380        if (_IOC_DIR(cmd) & _IOC_WRITE)
 381                inarg.in_size = size;
 382
 383        args.opcode = FUSE_IOCTL;
 384        args.nodeid = ff->nodeid;
 385        args.in_numargs = 2;
 386        args.in_args[0].size = sizeof(inarg);
 387        args.in_args[0].value = &inarg;
 388        args.in_args[1].size = inarg.in_size;
 389        args.in_args[1].value = ptr;
 390        args.out_numargs = 2;
 391        args.out_args[0].size = sizeof(outarg);
 392        args.out_args[0].value = &outarg;
 393        args.out_args[1].size = inarg.out_size;
 394        args.out_args[1].value = ptr;
 395
 396        err = fuse_simple_request(fm, &args);
 397        if (!err && outarg.flags & FUSE_IOCTL_RETRY)
 398                err = -EIO;
 399
 400        return err;
 401}
 402
 403static struct fuse_file *fuse_priv_ioctl_prepare(struct inode *inode)
 404{
 405        struct fuse_mount *fm = get_fuse_mount(inode);
 406        bool isdir = S_ISDIR(inode->i_mode);
 407
 408        if (!S_ISREG(inode->i_mode) && !isdir)
 409                return ERR_PTR(-ENOTTY);
 410
 411        return fuse_file_open(fm, get_node_id(inode), O_RDONLY, isdir);
 412}
 413
 414static void fuse_priv_ioctl_cleanup(struct inode *inode, struct fuse_file *ff)
 415{
 416        fuse_file_release(inode, ff, O_RDONLY, NULL, S_ISDIR(inode->i_mode));
 417}
 418
 419int fuse_fileattr_get(struct dentry *dentry, struct fileattr *fa)
 420{
 421        struct inode *inode = d_inode(dentry);
 422        struct fuse_file *ff;
 423        unsigned int flags;
 424        struct fsxattr xfa;
 425        int err;
 426
 427        ff = fuse_priv_ioctl_prepare(inode);
 428        if (IS_ERR(ff))
 429                return PTR_ERR(ff);
 430
 431        if (fa->flags_valid) {
 432                err = fuse_priv_ioctl(inode, ff, FS_IOC_GETFLAGS,
 433                                      &flags, sizeof(flags));
 434                if (err)
 435                        goto cleanup;
 436
 437                fileattr_fill_flags(fa, flags);
 438        } else {
 439                err = fuse_priv_ioctl(inode, ff, FS_IOC_FSGETXATTR,
 440                                      &xfa, sizeof(xfa));
 441                if (err)
 442                        goto cleanup;
 443
 444                fileattr_fill_xflags(fa, xfa.fsx_xflags);
 445                fa->fsx_extsize = xfa.fsx_extsize;
 446                fa->fsx_nextents = xfa.fsx_nextents;
 447                fa->fsx_projid = xfa.fsx_projid;
 448                fa->fsx_cowextsize = xfa.fsx_cowextsize;
 449        }
 450cleanup:
 451        fuse_priv_ioctl_cleanup(inode, ff);
 452
 453        return err;
 454}
 455
 456int fuse_fileattr_set(struct user_namespace *mnt_userns,
 457                      struct dentry *dentry, struct fileattr *fa)
 458{
 459        struct inode *inode = d_inode(dentry);
 460        struct fuse_file *ff;
 461        unsigned int flags = fa->flags;
 462        struct fsxattr xfa;
 463        int err;
 464
 465        ff = fuse_priv_ioctl_prepare(inode);
 466        if (IS_ERR(ff))
 467                return PTR_ERR(ff);
 468
 469        if (fa->flags_valid) {
 470                err = fuse_priv_ioctl(inode, ff, FS_IOC_SETFLAGS,
 471                                      &flags, sizeof(flags));
 472                if (err)
 473                        goto cleanup;
 474        } else {
 475                memset(&xfa, 0, sizeof(xfa));
 476                xfa.fsx_xflags = fa->fsx_xflags;
 477                xfa.fsx_extsize = fa->fsx_extsize;
 478                xfa.fsx_nextents = fa->fsx_nextents;
 479                xfa.fsx_projid = fa->fsx_projid;
 480                xfa.fsx_cowextsize = fa->fsx_cowextsize;
 481
 482                err = fuse_priv_ioctl(inode, ff, FS_IOC_FSSETXATTR,
 483                                      &xfa, sizeof(xfa));
 484        }
 485
 486cleanup:
 487        fuse_priv_ioctl_cleanup(inode, ff);
 488
 489        return err;
 490}
 491
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