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linux/fs/squashfs/squashfs_fs.h
Phillip Lougher f65c4bbbd6 Squashfs: fix handling and sanity checking of xattr_ids count 
A Sysbot [1] corrupted filesystem exposes two flaws in the handling and
sanity checking of the xattr_ids count in the filesystem.  Both of these
flaws cause computation overflow due to incorrect typing.

In the corrupted filesystem the xattr_ids value is 4294967071, which
stored in a signed variable becomes the negative number -225.

Flaw 1 (64-bit systems only):

The signed integer xattr_ids variable causes sign extension.

This causes variable overflow in the SQUASHFS_XATTR_*(A) macros.  The
variable is first multiplied by sizeof(struct squashfs_xattr_id) where the
type of the sizeof operator is "unsigned long".

On a 64-bit system this is 64-bits in size, and causes the negative number
to be sign extended and widened to 64-bits and then become unsigned.  This
produces the very large number 18446744073709548016 or 2^64 - 3600.  This
number when rounded up by SQUASHFS_METADATA_SIZE - 1 (8191 bytes) and
divided by SQUASHFS_METADATA_SIZE overflows and produces a length of 0
(stored in len).

Flaw 2 (32-bit systems only):

On a 32-bit system the integer variable is not widened by the unsigned
long type of the sizeof operator (32-bits), and the signedness of the
variable has no effect due it always being treated as unsigned.

The above corrupted xattr_ids value of 4294967071, when multiplied
overflows and produces the number 4294963696 or 2^32 - 3400.  This number
when rounded up by SQUASHFS_METADATA_SIZE - 1 (8191 bytes) and divided by
SQUASHFS_METADATA_SIZE overflows again and produces a length of 0.

The effect of the 0 length computation:

In conjunction with the corrupted xattr_ids field, the filesystem also has
a corrupted xattr_table_start value, where it matches the end of
filesystem value of 850.

This causes the following sanity check code to fail because the
incorrectly computed len of 0 matches the incorrect size of the table
reported by the superblock (0 bytes).

    len = SQUASHFS_XATTR_BLOCK_BYTES(*xattr_ids);
    indexes = SQUASHFS_XATTR_BLOCKS(*xattr_ids);

    /*
     * The computed size of the index table (len bytes) should exactly
     * match the table start and end points
    */
    start = table_start + sizeof(*id_table);
    end = msblk->bytes_used;

    if (len != (end - start))
            return ERR_PTR(-EINVAL);

Changing the xattr_ids variable to be "usigned int" fixes the flaw on a
64-bit system.  This relies on the fact the computation is widened by the
unsigned long type of the sizeof operator.

Casting the variable to u64 in the above macro fixes this flaw on a 32-bit
system.

It also means 64-bit systems do not implicitly rely on the type of the
sizeof operator to widen the computation.

[1] https://lore.kernel.org/lkml/000000000000cd44f005f1a0f17f@google.com/

Link: https://lkml.kernel.org/r/20230127061842.10965-1-phillip@squashfs.org.uk
Fixes: 506220d2ba ("squashfs: add more sanity checks in xattr id lookup")
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Reported-by: <syzbot+082fa4af80a5bb1a9843@syzkaller.appspotmail.com>
Cc: Alexey Khoroshilov <khoroshilov@ispras.ru>
Cc: Fedor Pchelkin <pchelkin@ispras.ru>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-01-31 16:44:10 -08:00

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/* SPDX-License-Identifier: GPL-2.0-or-later */
#ifndef SQUASHFS_FS
#define SQUASHFS_FS
/*
* Squashfs
*
* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
* Phillip Lougher <phillip@squashfs.org.uk>
*
* squashfs_fs.h
*/
#define SQUASHFS_CACHED_FRAGMENTS CONFIG_SQUASHFS_FRAGMENT_CACHE_SIZE
#define SQUASHFS_MAJOR 4
#define SQUASHFS_MINOR 0
#define SQUASHFS_START 0
/* size of metadata (inode and directory) blocks */
#define SQUASHFS_METADATA_SIZE 8192
#define SQUASHFS_BLOCK_OFFSET 2
/* default size of block device I/O */
#ifdef CONFIG_SQUASHFS_4K_DEVBLK_SIZE
#define SQUASHFS_DEVBLK_SIZE 4096
#else
#define SQUASHFS_DEVBLK_SIZE 1024
#endif
#define SQUASHFS_FILE_MAX_SIZE 1048576
#define SQUASHFS_FILE_MAX_LOG 20
/* Max length of filename (not 255) */
#define SQUASHFS_NAME_LEN 256
/* Max value for directory header count*/
#define SQUASHFS_DIR_COUNT 256
#define SQUASHFS_INVALID_FRAG (0xffffffffU)
#define SQUASHFS_INVALID_XATTR (0xffffffffU)
#define SQUASHFS_INVALID_BLK (-1LL)
/* Filesystem flags */
#define SQUASHFS_NOI 0
#define SQUASHFS_NOD 1
#define SQUASHFS_NOF 3
#define SQUASHFS_NO_FRAG 4
#define SQUASHFS_ALWAYS_FRAG 5
#define SQUASHFS_DUPLICATE 6
#define SQUASHFS_EXPORT 7
#define SQUASHFS_COMP_OPT 10
#define SQUASHFS_BIT(flag, bit) ((flag >> bit) & 1)
#define SQUASHFS_UNCOMPRESSED_INODES(flags) SQUASHFS_BIT(flags, \
SQUASHFS_NOI)
#define SQUASHFS_UNCOMPRESSED_DATA(flags) SQUASHFS_BIT(flags, \
SQUASHFS_NOD)
#define SQUASHFS_UNCOMPRESSED_FRAGMENTS(flags) SQUASHFS_BIT(flags, \
SQUASHFS_NOF)
#define SQUASHFS_NO_FRAGMENTS(flags) SQUASHFS_BIT(flags, \
SQUASHFS_NO_FRAG)
#define SQUASHFS_ALWAYS_FRAGMENTS(flags) SQUASHFS_BIT(flags, \
SQUASHFS_ALWAYS_FRAG)
#define SQUASHFS_DUPLICATES(flags) SQUASHFS_BIT(flags, \
SQUASHFS_DUPLICATE)
#define SQUASHFS_EXPORTABLE(flags) SQUASHFS_BIT(flags, \
SQUASHFS_EXPORT)
#define SQUASHFS_COMP_OPTS(flags) SQUASHFS_BIT(flags, \
SQUASHFS_COMP_OPT)
/* Inode types including extended types */
#define SQUASHFS_DIR_TYPE 1
#define SQUASHFS_REG_TYPE 2
#define SQUASHFS_SYMLINK_TYPE 3
#define SQUASHFS_BLKDEV_TYPE 4
#define SQUASHFS_CHRDEV_TYPE 5
#define SQUASHFS_FIFO_TYPE 6
#define SQUASHFS_SOCKET_TYPE 7
#define SQUASHFS_LDIR_TYPE 8
#define SQUASHFS_LREG_TYPE 9
#define SQUASHFS_LSYMLINK_TYPE 10
#define SQUASHFS_LBLKDEV_TYPE 11
#define SQUASHFS_LCHRDEV_TYPE 12
#define SQUASHFS_LFIFO_TYPE 13
#define SQUASHFS_LSOCKET_TYPE 14
/* Max type value stored in directory entry */
#define SQUASHFS_MAX_DIR_TYPE 7
/* Xattr types */
#define SQUASHFS_XATTR_USER 0
#define SQUASHFS_XATTR_TRUSTED 1
#define SQUASHFS_XATTR_SECURITY 2
#define SQUASHFS_XATTR_VALUE_OOL 256
#define SQUASHFS_XATTR_PREFIX_MASK 0xff
/* Flag whether block is compressed or uncompressed, bit is set if block is
* uncompressed */
#define SQUASHFS_COMPRESSED_BIT (1 << 15)
#define SQUASHFS_COMPRESSED_SIZE(B) (((B) & ~SQUASHFS_COMPRESSED_BIT) ? \
(B) & ~SQUASHFS_COMPRESSED_BIT : SQUASHFS_COMPRESSED_BIT)
#define SQUASHFS_COMPRESSED(B) (!((B) & SQUASHFS_COMPRESSED_BIT))
#define SQUASHFS_COMPRESSED_BIT_BLOCK (1 << 24)
#define SQUASHFS_COMPRESSED_SIZE_BLOCK(B) ((B) & \
~SQUASHFS_COMPRESSED_BIT_BLOCK)
#define SQUASHFS_COMPRESSED_BLOCK(B) (!((B) & SQUASHFS_COMPRESSED_BIT_BLOCK))
static inline int squashfs_block_size(__le32 raw)
{
u32 size = le32_to_cpu(raw);
return (size >> 25) ? -EIO : size;
}
/*
* Inode number ops. Inodes consist of a compressed block number, and an
* uncompressed offset within that block
*/
#define SQUASHFS_INODE_BLK(A) ((unsigned int) ((A) >> 16))
#define SQUASHFS_INODE_OFFSET(A) ((unsigned int) ((A) & 0xffff))
#define SQUASHFS_MKINODE(A, B) ((long long)(((long long) (A)\
<< 16) + (B)))
/* fragment and fragment table defines */
#define SQUASHFS_FRAGMENT_BYTES(A) \
((A) * sizeof(struct squashfs_fragment_entry))
#define SQUASHFS_FRAGMENT_INDEX(A) (SQUASHFS_FRAGMENT_BYTES(A) / \
SQUASHFS_METADATA_SIZE)
#define SQUASHFS_FRAGMENT_INDEX_OFFSET(A) (SQUASHFS_FRAGMENT_BYTES(A) % \
SQUASHFS_METADATA_SIZE)
#define SQUASHFS_FRAGMENT_INDEXES(A) ((SQUASHFS_FRAGMENT_BYTES(A) + \
SQUASHFS_METADATA_SIZE - 1) / \
SQUASHFS_METADATA_SIZE)
#define SQUASHFS_FRAGMENT_INDEX_BYTES(A) (SQUASHFS_FRAGMENT_INDEXES(A) *\
sizeof(u64))
/* inode lookup table defines */
#define SQUASHFS_LOOKUP_BYTES(A) ((A) * sizeof(u64))
#define SQUASHFS_LOOKUP_BLOCK(A) (SQUASHFS_LOOKUP_BYTES(A) / \
SQUASHFS_METADATA_SIZE)
#define SQUASHFS_LOOKUP_BLOCK_OFFSET(A) (SQUASHFS_LOOKUP_BYTES(A) % \
SQUASHFS_METADATA_SIZE)
#define SQUASHFS_LOOKUP_BLOCKS(A) ((SQUASHFS_LOOKUP_BYTES(A) + \
SQUASHFS_METADATA_SIZE - 1) / \
SQUASHFS_METADATA_SIZE)
#define SQUASHFS_LOOKUP_BLOCK_BYTES(A) (SQUASHFS_LOOKUP_BLOCKS(A) *\
sizeof(u64))
/* uid/gid lookup table defines */
#define SQUASHFS_ID_BYTES(A) ((A) * sizeof(unsigned int))
#define SQUASHFS_ID_BLOCK(A) (SQUASHFS_ID_BYTES(A) / \
SQUASHFS_METADATA_SIZE)
#define SQUASHFS_ID_BLOCK_OFFSET(A) (SQUASHFS_ID_BYTES(A) % \
SQUASHFS_METADATA_SIZE)
#define SQUASHFS_ID_BLOCKS(A) ((SQUASHFS_ID_BYTES(A) + \
SQUASHFS_METADATA_SIZE - 1) / \
SQUASHFS_METADATA_SIZE)
#define SQUASHFS_ID_BLOCK_BYTES(A) (SQUASHFS_ID_BLOCKS(A) *\
sizeof(u64))
/* xattr id lookup table defines */
#define SQUASHFS_XATTR_BYTES(A) (((u64) (A)) * sizeof(struct squashfs_xattr_id))
#define SQUASHFS_XATTR_BLOCK(A) (SQUASHFS_XATTR_BYTES(A) / \
SQUASHFS_METADATA_SIZE)
#define SQUASHFS_XATTR_BLOCK_OFFSET(A) (SQUASHFS_XATTR_BYTES(A) % \
SQUASHFS_METADATA_SIZE)
#define SQUASHFS_XATTR_BLOCKS(A) ((SQUASHFS_XATTR_BYTES(A) + \
SQUASHFS_METADATA_SIZE - 1) / \
SQUASHFS_METADATA_SIZE)
#define SQUASHFS_XATTR_BLOCK_BYTES(A) (SQUASHFS_XATTR_BLOCKS(A) *\
sizeof(u64))
#define SQUASHFS_XATTR_BLK(A) ((unsigned int) ((A) >> 16))
#define SQUASHFS_XATTR_OFFSET(A) ((unsigned int) ((A) & 0xffff))
/* cached data constants for filesystem */
#define SQUASHFS_CACHED_BLKS 8
/* meta index cache */
#define SQUASHFS_META_INDEXES (SQUASHFS_METADATA_SIZE / sizeof(unsigned int))
#define SQUASHFS_META_ENTRIES 127
#define SQUASHFS_META_SLOTS 8
struct meta_entry {
u64 data_block;
unsigned int index_block;
unsigned short offset;
unsigned short pad;
};
struct meta_index {
unsigned int inode_number;
unsigned int offset;
unsigned short entries;
unsigned short skip;
unsigned short locked;
unsigned short pad;
struct meta_entry meta_entry[SQUASHFS_META_ENTRIES];
};
/*
* definitions for structures on disk
*/
#define ZLIB_COMPRESSION 1
#define LZMA_COMPRESSION 2
#define LZO_COMPRESSION 3
#define XZ_COMPRESSION 4
#define LZ4_COMPRESSION 5
#define ZSTD_COMPRESSION 6
struct squashfs_super_block {
__le32 s_magic;
__le32 inodes;
__le32 mkfs_time;
__le32 block_size;
__le32 fragments;
__le16 compression;
__le16 block_log;
__le16 flags;
__le16 no_ids;
__le16 s_major;
__le16 s_minor;
__le64 root_inode;
__le64 bytes_used;
__le64 id_table_start;
__le64 xattr_id_table_start;
__le64 inode_table_start;
__le64 directory_table_start;
__le64 fragment_table_start;
__le64 lookup_table_start;
};
struct squashfs_dir_index {
__le32 index;
__le32 start_block;
__le32 size;
unsigned char name[];
};
struct squashfs_base_inode {
__le16 inode_type;
__le16 mode;
__le16 uid;
__le16 guid;
__le32 mtime;
__le32 inode_number;
};
struct squashfs_ipc_inode {
__le16 inode_type;
__le16 mode;
__le16 uid;
__le16 guid;
__le32 mtime;
__le32 inode_number;
__le32 nlink;
};
struct squashfs_lipc_inode {
__le16 inode_type;
__le16 mode;
__le16 uid;
__le16 guid;
__le32 mtime;
__le32 inode_number;
__le32 nlink;
__le32 xattr;
};
struct squashfs_dev_inode {
__le16 inode_type;
__le16 mode;
__le16 uid;
__le16 guid;
__le32 mtime;
__le32 inode_number;
__le32 nlink;
__le32 rdev;
};
struct squashfs_ldev_inode {
__le16 inode_type;
__le16 mode;
__le16 uid;
__le16 guid;
__le32 mtime;
__le32 inode_number;
__le32 nlink;
__le32 rdev;
__le32 xattr;
};
struct squashfs_symlink_inode {
__le16 inode_type;
__le16 mode;
__le16 uid;
__le16 guid;
__le32 mtime;
__le32 inode_number;
__le32 nlink;
__le32 symlink_size;
char symlink[];
};
struct squashfs_reg_inode {
__le16 inode_type;
__le16 mode;
__le16 uid;
__le16 guid;
__le32 mtime;
__le32 inode_number;
__le32 start_block;
__le32 fragment;
__le32 offset;
__le32 file_size;
__le16 block_list[];
};
struct squashfs_lreg_inode {
__le16 inode_type;
__le16 mode;
__le16 uid;
__le16 guid;
__le32 mtime;
__le32 inode_number;
__le64 start_block;
__le64 file_size;
__le64 sparse;
__le32 nlink;
__le32 fragment;
__le32 offset;
__le32 xattr;
__le16 block_list[];
};
struct squashfs_dir_inode {
__le16 inode_type;
__le16 mode;
__le16 uid;
__le16 guid;
__le32 mtime;
__le32 inode_number;
__le32 start_block;
__le32 nlink;
__le16 file_size;
__le16 offset;
__le32 parent_inode;
};
struct squashfs_ldir_inode {
__le16 inode_type;
__le16 mode;
__le16 uid;
__le16 guid;
__le32 mtime;
__le32 inode_number;
__le32 nlink;
__le32 file_size;
__le32 start_block;
__le32 parent_inode;
__le16 i_count;
__le16 offset;
__le32 xattr;
struct squashfs_dir_index index[];
};
union squashfs_inode {
struct squashfs_base_inode base;
struct squashfs_dev_inode dev;
struct squashfs_ldev_inode ldev;
struct squashfs_symlink_inode symlink;
struct squashfs_reg_inode reg;
struct squashfs_lreg_inode lreg;
struct squashfs_dir_inode dir;
struct squashfs_ldir_inode ldir;
struct squashfs_ipc_inode ipc;
struct squashfs_lipc_inode lipc;
};
struct squashfs_dir_entry {
__le16 offset;
__le16 inode_number;
__le16 type;
__le16 size;
char name[];
};
struct squashfs_dir_header {
__le32 count;
__le32 start_block;
__le32 inode_number;
};
struct squashfs_fragment_entry {
__le64 start_block;
__le32 size;
unsigned int unused;
};
struct squashfs_xattr_entry {
__le16 type;
__le16 size;
char data[];
};
struct squashfs_xattr_val {
__le32 vsize;
char value[];
};
struct squashfs_xattr_id {
__le64 xattr;
__le32 count;
__le32 size;
};
struct squashfs_xattr_id_table {
__le64 xattr_table_start;
__le32 xattr_ids;
__le32 unused;
};
#endif
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