index.c

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/*
 * index.c - NTFS kernel index handling.  Part of the Linux-NTFS project.
 *
 * Copyright (c) 2004-2005 Anton Altaparmakov
 *
 * This program/include file is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program/include file is distributed in the hope that it will be
 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program (in the main directory of the Linux-NTFS
 * distribution in the file COPYING); if not, write to the Free Software
 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/slab.h>

#include "aops.h"
#include "collate.h"
#include "debug.h"
#include "index.h"
#include "ntfs.h"

ntfs_index_context *ntfs_index_ctx_get(ntfs_inode *idx_ni)
{
    ntfs_index_context *ictx;

    ictx = kmem_cache_alloc(ntfs_index_ctx_cache, GFP_NOFS);
    if (ictx)
        *ictx = (ntfs_index_context){ .idx_ni = idx_ni };
    return ictx;
}

void ntfs_index_ctx_put(ntfs_index_context *ictx)
{
    if (ictx->entry) {
        if (ictx->is_in_root) {
            if (ictx->actx)
                ntfs_attr_put_search_ctx(ictx->actx);
            if (ictx->base_ni)
                unmap_mft_record(ictx->base_ni);
        } else {
            struct page *page = ictx->page;
            if (page) {
                BUG_ON(!PageLocked(page));
                unlock_page(page);
                ntfs_unmap_page(page);
            }
        }
    }
    kmem_cache_free(ntfs_index_ctx_cache, ictx);
    return;
}

int ntfs_index_lookup(const void *key, const int key_len,
        ntfs_index_context *ictx)
{
    VCN vcn, old_vcn;
    ntfs_inode *idx_ni = ictx->idx_ni;
    ntfs_volume *vol = idx_ni->vol;
    struct super_block *sb = vol->sb;
    ntfs_inode *base_ni = idx_ni->ext.base_ntfs_ino;
    MFT_RECORD *m;
    INDEX_ROOT *ir;
    INDEX_ENTRY *ie;
    INDEX_ALLOCATION *ia;
    u8 *index_end, *kaddr;
    ntfs_attr_search_ctx *actx;
    struct address_space *ia_mapping;
    struct page *page;
    int rc, err = 0;

    ntfs_debug("Entering.");
    BUG_ON(!NInoAttr(idx_ni));
    BUG_ON(idx_ni->type != AT_INDEX_ALLOCATION);
    BUG_ON(idx_ni->nr_extents != -1);
    BUG_ON(!base_ni);
    BUG_ON(!key);
    BUG_ON(key_len <= 0);
    if (!ntfs_is_collation_rule_supported(
            idx_ni->itype.index.collation_rule)) {
        ntfs_error(sb, "Index uses unsupported collation rule 0x%x.  "
                "Aborting lookup.", le32_to_cpu(
                idx_ni->itype.index.collation_rule));
        return -EOPNOTSUPP;
    }
    /* Get hold of the mft record for the index inode. */
    m = map_mft_record(base_ni);
    if (IS_ERR(m)) {
        ntfs_error(sb, "map_mft_record() failed with error code %ld.",
                -PTR_ERR(m));
        return PTR_ERR(m);
    }
    actx = ntfs_attr_get_search_ctx(base_ni, m);
    if (unlikely(!actx)) {
        err = -ENOMEM;
        goto err_out;
    }
    /* Find the index root attribute in the mft record. */
    err = ntfs_attr_lookup(AT_INDEX_ROOT, idx_ni->name, idx_ni->name_len,
            CASE_SENSITIVE, 0, NULL, 0, actx);
    if (unlikely(err)) {
        if (err == -ENOENT) {
            ntfs_error(sb, "Index root attribute missing in inode "
                    "0x%lx.", idx_ni->mft_no);
            err = -EIO;
        }
        goto err_out;
    }
    /* Get to the index root value (it has been verified in read_inode). */
    ir = (INDEX_ROOT*)((u8*)actx->attr +
            le16_to_cpu(actx->attr->data.resident.value_offset));
    index_end = (u8*)&ir->index + le32_to_cpu(ir->index.index_length);
    /* The first index entry. */
    ie = (INDEX_ENTRY*)((u8*)&ir->index +
            le32_to_cpu(ir->index.entries_offset));
    /*
     * Loop until we exceed valid memory (corruption case) or until we
     * reach the last entry.
     */
    for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
        /* Bounds checks. */
        if ((u8*)ie < (u8*)actx->mrec || (u8*)ie +
                sizeof(INDEX_ENTRY_HEADER) > index_end ||
                (u8*)ie + le16_to_cpu(ie->length) > index_end)
            goto idx_err_out;
        /*
         * The last entry cannot contain a key.  It can however contain
         * a pointer to a child node in the B+tree so we just break out.
         */
        if (ie->flags & INDEX_ENTRY_END)
            break;
        /* Further bounds checks. */
        if ((u32)sizeof(INDEX_ENTRY_HEADER) +
                le16_to_cpu(ie->key_length) >
                le16_to_cpu(ie->data.vi.data_offset) ||
                (u32)le16_to_cpu(ie->data.vi.data_offset) +
                le16_to_cpu(ie->data.vi.data_length) >
                le16_to_cpu(ie->length))
            goto idx_err_out;
        /* If the keys match perfectly, we setup @ictx and return 0. */
        if ((key_len == le16_to_cpu(ie->key_length)) && !memcmp(key,
                &ie->key, key_len)) {
ir_done:
            ictx->is_in_root = true;
            ictx->ir = ir;
            ictx->actx = actx;
            ictx->base_ni = base_ni;
            ictx->ia = NULL;
            ictx->page = NULL;
done:
            ictx->entry = ie;
            ictx->data = (u8*)ie +
                    le16_to_cpu(ie->data.vi.data_offset);
            ictx->data_len = le16_to_cpu(ie->data.vi.data_length);
            ntfs_debug("Done.");
            return err;
        }
        /*
         * Not a perfect match, need to do full blown collation so we
         * know which way in the B+tree we have to go.
         */
        rc = ntfs_collate(vol, idx_ni->itype.index.collation_rule, key,
                key_len, &ie->key, le16_to_cpu(ie->key_length));
        /*
         * If @key collates before the key of the current entry, there
         * is definitely no such key in this index but we might need to
         * descend into the B+tree so we just break out of the loop.
         */
        if (rc == -1)
            break;
        /*
         * A match should never happen as the memcmp() call should have
         * cought it, but we still treat it correctly.
         */
        if (!rc)
            goto ir_done;
        /* The keys are not equal, continue the search. */
    }
    /*
     * We have finished with this index without success.  Check for the
     * presence of a child node and if not present setup @ictx and return
     * -ENOENT.
     */
    if (!(ie->flags & INDEX_ENTRY_NODE)) {
        ntfs_debug("Entry not found.");
        err = -ENOENT;
        goto ir_done;
    } /* Child node present, descend into it. */
    /* Consistency check: Verify that an index allocation exists. */
    if (!NInoIndexAllocPresent(idx_ni)) {
        ntfs_error(sb, "No index allocation attribute but index entry "
                "requires one.  Inode 0x%lx is corrupt or "
                "driver bug.", idx_ni->mft_no);
        goto err_out;
    }
    /* Get the starting vcn of the index_block holding the child node. */
    vcn = sle64_to_cpup((sle64*)((u8*)ie + le16_to_cpu(ie->length) - 8));
    ia_mapping = VFS_I(idx_ni)->i_mapping;
    /*
     * We are done with the index root and the mft record.  Release them,
     * otherwise we deadlock with ntfs_map_page().
     */
    ntfs_attr_put_search_ctx(actx);
    unmap_mft_record(base_ni);
    m = NULL;
    actx = NULL;
descend_into_child_node:
    /*
     * Convert vcn to index into the index allocation attribute in units
     * of PAGE_CACHE_SIZE and map the page cache page, reading it from
     * disk if necessary.
     */
    page = ntfs_map_page(ia_mapping, vcn <<
            idx_ni->itype.index.vcn_size_bits >> PAGE_CACHE_SHIFT);
    if (IS_ERR(page)) {
        ntfs_error(sb, "Failed to map index page, error %ld.",
                -PTR_ERR(page));
        err = PTR_ERR(page);
        goto err_out;
    }
    lock_page(page);
    kaddr = (u8*)page_address(page);
fast_descend_into_child_node:
    /* Get to the index allocation block. */
    ia = (INDEX_ALLOCATION*)(kaddr + ((vcn <<
            idx_ni->itype.index.vcn_size_bits) & ~PAGE_CACHE_MASK));
    /* Bounds checks. */
    if ((u8*)ia < kaddr || (u8*)ia > kaddr + PAGE_CACHE_SIZE) {
        ntfs_error(sb, "Out of bounds check failed.  Corrupt inode "
                "0x%lx or driver bug.", idx_ni->mft_no);
        goto unm_err_out;
    }
    /* Catch multi sector transfer fixup errors. */
    if (unlikely(!ntfs_is_indx_record(ia->magic))) {
        ntfs_error(sb, "Index record with vcn 0x%llx is corrupt.  "
                "Corrupt inode 0x%lx.  Run chkdsk.",
                (long long)vcn, idx_ni->mft_no);
        goto unm_err_out;
    }
    if (sle64_to_cpu(ia->index_block_vcn) != vcn) {
        ntfs_error(sb, "Actual VCN (0x%llx) of index buffer is "
                "different from expected VCN (0x%llx).  Inode "
                "0x%lx is corrupt or driver bug.",
                (unsigned long long)
                sle64_to_cpu(ia->index_block_vcn),
                (unsigned long long)vcn, idx_ni->mft_no);
        goto unm_err_out;
    }
    if (le32_to_cpu(ia->index.allocated_size) + 0x18 !=
            idx_ni->itype.index.block_size) {
        ntfs_error(sb, "Index buffer (VCN 0x%llx) of inode 0x%lx has "
                "a size (%u) differing from the index "
                "specified size (%u).  Inode is corrupt or "
                "driver bug.", (unsigned long long)vcn,
                idx_ni->mft_no,
                le32_to_cpu(ia->index.allocated_size) + 0x18,
                idx_ni->itype.index.block_size);
        goto unm_err_out;
    }
    index_end = (u8*)ia + idx_ni->itype.index.block_size;
    if (index_end > kaddr + PAGE_CACHE_SIZE) {
        ntfs_error(sb, "Index buffer (VCN 0x%llx) of inode 0x%lx "
                "crosses page boundary.  Impossible!  Cannot "
                "access!  This is probably a bug in the "
                "driver.", (unsigned long long)vcn,
                idx_ni->mft_no);
        goto unm_err_out;
    }
    index_end = (u8*)&ia->index + le32_to_cpu(ia->index.index_length);
    if (index_end > (u8*)ia + idx_ni->itype.index.block_size) {
        ntfs_error(sb, "Size of index buffer (VCN 0x%llx) of inode "
                "0x%lx exceeds maximum size.",
                (unsigned long long)vcn, idx_ni->mft_no);
        goto unm_err_out;
    }
    /* The first index entry. */
    ie = (INDEX_ENTRY*)((u8*)&ia->index +
            le32_to_cpu(ia->index.entries_offset));
    /*
     * Iterate similar to above big loop but applied to index buffer, thus
     * loop until we exceed valid memory (corruption case) or until we
     * reach the last entry.
     */
    for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
        /* Bounds checks. */
        if ((u8*)ie < (u8*)ia || (u8*)ie +
                sizeof(INDEX_ENTRY_HEADER) > index_end ||
                (u8*)ie + le16_to_cpu(ie->length) > index_end) {
            ntfs_error(sb, "Index entry out of bounds in inode "
                    "0x%lx.", idx_ni->mft_no);
            goto unm_err_out;
        }
        /*
         * The last entry cannot contain a key.  It can however contain
         * a pointer to a child node in the B+tree so we just break out.
         */
        if (ie->flags & INDEX_ENTRY_END)
            break;
        /* Further bounds checks. */
        if ((u32)sizeof(INDEX_ENTRY_HEADER) +
                le16_to_cpu(ie->key_length) >
                le16_to_cpu(ie->data.vi.data_offset) ||
                (u32)le16_to_cpu(ie->data.vi.data_offset) +
                le16_to_cpu(ie->data.vi.data_length) >
                le16_to_cpu(ie->length)) {
            ntfs_error(sb, "Index entry out of bounds in inode "
                    "0x%lx.", idx_ni->mft_no);
            goto unm_err_out;
        }
        /* If the keys match perfectly, we setup @ictx and return 0. */
        if ((key_len == le16_to_cpu(ie->key_length)) && !memcmp(key,
                &ie->key, key_len)) {
ia_done:
            ictx->is_in_root = false;
            ictx->actx = NULL;
            ictx->base_ni = NULL;
            ictx->ia = ia;
            ictx->page = page;
            goto done;
        }
        /*
         * Not a perfect match, need to do full blown collation so we
         * know which way in the B+tree we have to go.
         */
        rc = ntfs_collate(vol, idx_ni->itype.index.collation_rule, key,
                key_len, &ie->key, le16_to_cpu(ie->key_length));
        /*
         * If @key collates before the key of the current entry, there
         * is definitely no such key in this index but we might need to
         * descend into the B+tree so we just break out of the loop.
         */
        if (rc == -1)
            break;
        /*
         * A match should never happen as the memcmp() call should have
         * cought it, but we still treat it correctly.
         */
        if (!rc)
            goto ia_done;
        /* The keys are not equal, continue the search. */
    }
    /*
     * We have finished with this index buffer without success.  Check for
     * the presence of a child node and if not present return -ENOENT.
     */
    if (!(ie->flags & INDEX_ENTRY_NODE)) {
        ntfs_debug("Entry not found.");
        err = -ENOENT;
        goto ia_done;
    }
    if ((ia->index.flags & NODE_MASK) == LEAF_NODE) {
        ntfs_error(sb, "Index entry with child node found in a leaf "
                "node in inode 0x%lx.", idx_ni->mft_no);
        goto unm_err_out;
    }
    /* Child node present, descend into it. */
    old_vcn = vcn;
    vcn = sle64_to_cpup((sle64*)((u8*)ie + le16_to_cpu(ie->length) - 8));
    if (vcn >= 0) {
        /*
         * If vcn is in the same page cache page as old_vcn we recycle
         * the mapped page.
         */
        if (old_vcn << vol->cluster_size_bits >>
                PAGE_CACHE_SHIFT == vcn <<
                vol->cluster_size_bits >>
                PAGE_CACHE_SHIFT)
            goto fast_descend_into_child_node;
        unlock_page(page);
        ntfs_unmap_page(page);
        goto descend_into_child_node;
    }
    ntfs_error(sb, "Negative child node vcn in inode 0x%lx.",
            idx_ni->mft_no);
unm_err_out:
    unlock_page(page);
    ntfs_unmap_page(page);
err_out:
    if (!err)
        err = -EIO;
    if (actx)
        ntfs_attr_put_search_ctx(actx);
    if (m)
        unmap_mft_record(base_ni);
    return err;
idx_err_out:
    ntfs_error(sb, "Corrupt index.  Aborting lookup.");
    goto err_out;
}