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a814355e70
commit f37aa4c7366e23f91b81d00bafd6a7ab54e4a381 upstream. Sysbot has reported a number of "slab-out-of-bounds reads" and "use-after-free read" errors which has been identified as being caused by a corrupted index value read from the inode. This could be because the metadata block is uncompressed, or because the "compression" bit has been corrupted (turning a compressed block into an uncompressed block). This patch adds additional sanity checks to detect this, and the following corruption. 1. It checks against corruption of the ids count. This can either lead to a larger table to be read, or a smaller than expected table to be read. In the case of a too large ids count, this would often have been trapped by the existing sanity checks, but this patch introduces a more exact check, which can identify too small values. 2. It checks the contents of the index table for corruption. Link: https://lkml.kernel.org/r/20210204130249.4495-3-phillip@squashfs.org.uk Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk> Reported-by: syzbot+b06d57ba83f604522af2@syzkaller.appspotmail.com Reported-by: syzbot+c021ba012da41ee9807c@syzkaller.appspotmail.com Reported-by: syzbot+5024636e8b5fd19f0f19@syzkaller.appspotmail.com Reported-by: syzbot+bcbc661df46657d0fa4f@syzkaller.appspotmail.com Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
114 lines
3.0 KiB
C
114 lines
3.0 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Squashfs - a compressed read only filesystem for Linux
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*
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* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
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* Phillip Lougher <phillip@squashfs.org.uk>
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*
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* id.c
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*/
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/*
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* This file implements code to handle uids and gids.
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*
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* For space efficiency regular files store uid and gid indexes, which are
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* converted to 32-bit uids/gids using an id look up table. This table is
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* stored compressed into metadata blocks. A second index table is used to
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* locate these. This second index table for speed of access (and because it
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* is small) is read at mount time and cached in memory.
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*/
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#include <linux/fs.h>
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#include <linux/vfs.h>
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#include <linux/slab.h>
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#include "squashfs_fs.h"
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#include "squashfs_fs_sb.h"
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#include "squashfs.h"
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/*
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* Map uid/gid index into real 32-bit uid/gid using the id look up table
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*/
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int squashfs_get_id(struct super_block *sb, unsigned int index,
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unsigned int *id)
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{
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struct squashfs_sb_info *msblk = sb->s_fs_info;
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int block = SQUASHFS_ID_BLOCK(index);
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int offset = SQUASHFS_ID_BLOCK_OFFSET(index);
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u64 start_block;
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__le32 disk_id;
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int err;
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if (index >= msblk->ids)
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return -EINVAL;
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start_block = le64_to_cpu(msblk->id_table[block]);
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err = squashfs_read_metadata(sb, &disk_id, &start_block, &offset,
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sizeof(disk_id));
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if (err < 0)
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return err;
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*id = le32_to_cpu(disk_id);
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return 0;
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}
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/*
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* Read uncompressed id lookup table indexes from disk into memory
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*/
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__le64 *squashfs_read_id_index_table(struct super_block *sb,
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u64 id_table_start, u64 next_table, unsigned short no_ids)
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{
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unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids);
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unsigned int indexes = SQUASHFS_ID_BLOCKS(no_ids);
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int n;
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__le64 *table;
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u64 start, end;
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TRACE("In read_id_index_table, length %d\n", length);
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/* Sanity check values */
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/* there should always be at least one id */
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if (no_ids == 0)
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return ERR_PTR(-EINVAL);
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/*
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* The computed size of the index table (length bytes) should exactly
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* match the table start and end points
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*/
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if (length != (next_table - id_table_start))
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return ERR_PTR(-EINVAL);
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table = squashfs_read_table(sb, id_table_start, length);
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if (IS_ERR(table))
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return table;
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/*
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* table[0], table[1], ... table[indexes - 1] store the locations
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* of the compressed id blocks. Each entry should be less than
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* the next (i.e. table[0] < table[1]), and the difference between them
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* should be SQUASHFS_METADATA_SIZE or less. table[indexes - 1]
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* should be less than id_table_start, and again the difference
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* should be SQUASHFS_METADATA_SIZE or less
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*/
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for (n = 0; n < (indexes - 1); n++) {
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start = le64_to_cpu(table[n]);
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end = le64_to_cpu(table[n + 1]);
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if (start >= end || (end - start) > SQUASHFS_METADATA_SIZE) {
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kfree(table);
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return ERR_PTR(-EINVAL);
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}
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}
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start = le64_to_cpu(table[indexes - 1]);
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if (start >= id_table_start || (id_table_start - start) > SQUASHFS_METADATA_SIZE) {
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kfree(table);
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return ERR_PTR(-EINVAL);
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}
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return table;
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}
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