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linux/fs/squashfs/inode.c
Phillip Lougher 9253c54e01 Squashfs: check the inode number is not the invalid value of zero 
Syskiller has produced an out of bounds access in fill_meta_index().

That out of bounds access is ultimately caused because the inode
has an inode number with the invalid value of zero, which was not checked.

The reason this causes the out of bounds access is due to following
sequence of events:

1. Fill_meta_index() is called to allocate (via empty_meta_index())
   and fill a metadata index.  It however suffers a data read error
   and aborts, invalidating the newly returned empty metadata index.
   It does this by setting the inode number of the index to zero,
   which means unused (zero is not a valid inode number).

2. When fill_meta_index() is subsequently called again on another
   read operation, locate_meta_index() returns the previous index
   because it matches the inode number of 0.  Because this index
   has been returned it is expected to have been filled, and because
   it hasn't been, an out of bounds access is performed.

This patch adds a sanity check which checks that the inode number
is not zero when the inode is created and returns -EINVAL if it is.

[phillip@squashfs.org.uk: whitespace fix]
  Link: https://lkml.kernel.org/r/20240409204723.446925-1-phillip@squashfs.org.uk
Link: https://lkml.kernel.org/r/20240408220206.435788-1-phillip@squashfs.org.uk
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Reported-by: "Ubisectech Sirius" <bugreport@ubisectech.com>
Closes: https://lore.kernel.org/lkml/87f5c007-b8a5-41ae-8b57-431e924c5915.bugreport@ubisectech.com/
Cc: Christian Brauner <brauner@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-04-16 15:39:50 -07:00

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Squashfs - a compressed read only filesystem for Linux
*
* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
* Phillip Lougher <phillip@squashfs.org.uk>
*
* inode.c
*/
/*
* This file implements code to create and read inodes from disk.
*
* Inodes in Squashfs are identified by a 48-bit inode which encodes the
* location of the compressed metadata block containing the inode, and the byte
* offset into that block where the inode is placed (<block, offset>).
*
* To maximise compression there are different inodes for each file type
* (regular file, directory, device, etc.), the inode contents and length
* varying with the type.
*
* To further maximise compression, two types of regular file inode and
* directory inode are defined: inodes optimised for frequently occurring
* regular files and directories, and extended types where extra
* information has to be stored.
*/
#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/xattr.h>
#include <linux/pagemap.h>
#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs_fs_i.h"
#include "squashfs.h"
#include "xattr.h"
/*
* Initialise VFS inode with the base inode information common to all
* Squashfs inode types. Sqsh_ino contains the unswapped base inode
* off disk.
*/
static int squashfs_new_inode(struct super_block *sb, struct inode *inode,
struct squashfs_base_inode *sqsh_ino)
{
uid_t i_uid;
gid_t i_gid;
int err;
inode->i_ino = le32_to_cpu(sqsh_ino->inode_number);
if (inode->i_ino == 0)
return -EINVAL;
err = squashfs_get_id(sb, le16_to_cpu(sqsh_ino->uid), &i_uid);
if (err)
return err;
err = squashfs_get_id(sb, le16_to_cpu(sqsh_ino->guid), &i_gid);
if (err)
return err;
i_uid_write(inode, i_uid);
i_gid_write(inode, i_gid);
inode_set_mtime(inode, le32_to_cpu(sqsh_ino->mtime), 0);
inode_set_atime(inode, inode_get_mtime_sec(inode), 0);
inode_set_ctime(inode, inode_get_mtime_sec(inode), 0);
inode->i_mode = le16_to_cpu(sqsh_ino->mode);
inode->i_size = 0;
return err;
}
struct inode *squashfs_iget(struct super_block *sb, long long ino,
unsigned int ino_number)
{
struct inode *inode = iget_locked(sb, ino_number);
int err;
TRACE("Entered squashfs_iget\n");
if (!inode)
return ERR_PTR(-ENOMEM);
if (!(inode->i_state & I_NEW))
return inode;
err = squashfs_read_inode(inode, ino);
if (err) {
iget_failed(inode);
return ERR_PTR(err);
}
unlock_new_inode(inode);
return inode;
}
/*
* Initialise VFS inode by reading inode from inode table (compressed
* metadata). The format and amount of data read depends on type.
*/
int squashfs_read_inode(struct inode *inode, long long ino)
{
struct super_block *sb = inode->i_sb;
struct squashfs_sb_info *msblk = sb->s_fs_info;
u64 block = SQUASHFS_INODE_BLK(ino) + msblk->inode_table;
int err, type, offset = SQUASHFS_INODE_OFFSET(ino);
union squashfs_inode squashfs_ino;
struct squashfs_base_inode *sqshb_ino = &squashfs_ino.base;
int xattr_id = SQUASHFS_INVALID_XATTR;
TRACE("Entered squashfs_read_inode\n");
/*
* Read inode base common to all inode types.
*/
err = squashfs_read_metadata(sb, sqshb_ino, &block,
&offset, sizeof(*sqshb_ino));
if (err < 0)
goto failed_read;
err = squashfs_new_inode(sb, inode, sqshb_ino);
if (err)
goto failed_read;
block = SQUASHFS_INODE_BLK(ino) + msblk->inode_table;
offset = SQUASHFS_INODE_OFFSET(ino);
type = le16_to_cpu(sqshb_ino->inode_type);
switch (type) {
case SQUASHFS_REG_TYPE: {
unsigned int frag_offset, frag;
int frag_size;
u64 frag_blk;
struct squashfs_reg_inode *sqsh_ino = &squashfs_ino.reg;
err = squashfs_read_metadata(sb, sqsh_ino, &block, &offset,
sizeof(*sqsh_ino));
if (err < 0)
goto failed_read;
frag = le32_to_cpu(sqsh_ino->fragment);
if (frag != SQUASHFS_INVALID_FRAG) {
frag_offset = le32_to_cpu(sqsh_ino->offset);
frag_size = squashfs_frag_lookup(sb, frag, &frag_blk);
if (frag_size < 0) {
err = frag_size;
goto failed_read;
}
} else {
frag_blk = SQUASHFS_INVALID_BLK;
frag_size = 0;
frag_offset = 0;
}
set_nlink(inode, 1);
inode->i_size = le32_to_cpu(sqsh_ino->file_size);
inode->i_fop = &generic_ro_fops;
inode->i_mode |= S_IFREG;
inode->i_blocks = ((inode->i_size - 1) >> 9) + 1;
squashfs_i(inode)->fragment_block = frag_blk;
squashfs_i(inode)->fragment_size = frag_size;
squashfs_i(inode)->fragment_offset = frag_offset;
squashfs_i(inode)->start = le32_to_cpu(sqsh_ino->start_block);
squashfs_i(inode)->block_list_start = block;
squashfs_i(inode)->offset = offset;
inode->i_data.a_ops = &squashfs_aops;
TRACE("File inode %x:%x, start_block %llx, block_list_start "
"%llx, offset %x\n", SQUASHFS_INODE_BLK(ino),
offset, squashfs_i(inode)->start, block, offset);
break;
}
case SQUASHFS_LREG_TYPE: {
unsigned int frag_offset, frag;
int frag_size;
u64 frag_blk;
struct squashfs_lreg_inode *sqsh_ino = &squashfs_ino.lreg;
err = squashfs_read_metadata(sb, sqsh_ino, &block, &offset,
sizeof(*sqsh_ino));
if (err < 0)
goto failed_read;
frag = le32_to_cpu(sqsh_ino->fragment);
if (frag != SQUASHFS_INVALID_FRAG) {
frag_offset = le32_to_cpu(sqsh_ino->offset);
frag_size = squashfs_frag_lookup(sb, frag, &frag_blk);
if (frag_size < 0) {
err = frag_size;
goto failed_read;
}
} else {
frag_blk = SQUASHFS_INVALID_BLK;
frag_size = 0;
frag_offset = 0;
}
xattr_id = le32_to_cpu(sqsh_ino->xattr);
set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
inode->i_size = le64_to_cpu(sqsh_ino->file_size);
inode->i_op = &squashfs_inode_ops;
inode->i_fop = &generic_ro_fops;
inode->i_mode |= S_IFREG;
inode->i_blocks = (inode->i_size -
le64_to_cpu(sqsh_ino->sparse) + 511) >> 9;
squashfs_i(inode)->fragment_block = frag_blk;
squashfs_i(inode)->fragment_size = frag_size;
squashfs_i(inode)->fragment_offset = frag_offset;
squashfs_i(inode)->start = le64_to_cpu(sqsh_ino->start_block);
squashfs_i(inode)->block_list_start = block;
squashfs_i(inode)->offset = offset;
inode->i_data.a_ops = &squashfs_aops;
TRACE("File inode %x:%x, start_block %llx, block_list_start "
"%llx, offset %x\n", SQUASHFS_INODE_BLK(ino),
offset, squashfs_i(inode)->start, block, offset);
break;
}
case SQUASHFS_DIR_TYPE: {
struct squashfs_dir_inode *sqsh_ino = &squashfs_ino.dir;
err = squashfs_read_metadata(sb, sqsh_ino, &block, &offset,
sizeof(*sqsh_ino));
if (err < 0)
goto failed_read;
set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
inode->i_size = le16_to_cpu(sqsh_ino->file_size);
inode->i_op = &squashfs_dir_inode_ops;
inode->i_fop = &squashfs_dir_ops;
inode->i_mode |= S_IFDIR;
squashfs_i(inode)->start = le32_to_cpu(sqsh_ino->start_block);
squashfs_i(inode)->offset = le16_to_cpu(sqsh_ino->offset);
squashfs_i(inode)->dir_idx_cnt = 0;
squashfs_i(inode)->parent = le32_to_cpu(sqsh_ino->parent_inode);
TRACE("Directory inode %x:%x, start_block %llx, offset %x\n",
SQUASHFS_INODE_BLK(ino), offset,
squashfs_i(inode)->start,
le16_to_cpu(sqsh_ino->offset));
break;
}
case SQUASHFS_LDIR_TYPE: {
struct squashfs_ldir_inode *sqsh_ino = &squashfs_ino.ldir;
err = squashfs_read_metadata(sb, sqsh_ino, &block, &offset,
sizeof(*sqsh_ino));
if (err < 0)
goto failed_read;
xattr_id = le32_to_cpu(sqsh_ino->xattr);
set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
inode->i_size = le32_to_cpu(sqsh_ino->file_size);
inode->i_op = &squashfs_dir_inode_ops;
inode->i_fop = &squashfs_dir_ops;
inode->i_mode |= S_IFDIR;
squashfs_i(inode)->start = le32_to_cpu(sqsh_ino->start_block);
squashfs_i(inode)->offset = le16_to_cpu(sqsh_ino->offset);
squashfs_i(inode)->dir_idx_start = block;
squashfs_i(inode)->dir_idx_offset = offset;
squashfs_i(inode)->dir_idx_cnt = le16_to_cpu(sqsh_ino->i_count);
squashfs_i(inode)->parent = le32_to_cpu(sqsh_ino->parent_inode);
TRACE("Long directory inode %x:%x, start_block %llx, offset "
"%x\n", SQUASHFS_INODE_BLK(ino), offset,
squashfs_i(inode)->start,
le16_to_cpu(sqsh_ino->offset));
break;
}
case SQUASHFS_SYMLINK_TYPE:
case SQUASHFS_LSYMLINK_TYPE: {
struct squashfs_symlink_inode *sqsh_ino = &squashfs_ino.symlink;
err = squashfs_read_metadata(sb, sqsh_ino, &block, &offset,
sizeof(*sqsh_ino));
if (err < 0)
goto failed_read;
set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
inode->i_size = le32_to_cpu(sqsh_ino->symlink_size);
inode->i_op = &squashfs_symlink_inode_ops;
inode_nohighmem(inode);
inode->i_data.a_ops = &squashfs_symlink_aops;
inode->i_mode |= S_IFLNK;
squashfs_i(inode)->start = block;
squashfs_i(inode)->offset = offset;
if (type == SQUASHFS_LSYMLINK_TYPE) {
__le32 xattr;
err = squashfs_read_metadata(sb, NULL, &block,
&offset, inode->i_size);
if (err < 0)
goto failed_read;
err = squashfs_read_metadata(sb, &xattr, &block,
&offset, sizeof(xattr));
if (err < 0)
goto failed_read;
xattr_id = le32_to_cpu(xattr);
}
TRACE("Symbolic link inode %x:%x, start_block %llx, offset "
"%x\n", SQUASHFS_INODE_BLK(ino), offset,
block, offset);
break;
}
case SQUASHFS_BLKDEV_TYPE:
case SQUASHFS_CHRDEV_TYPE: {
struct squashfs_dev_inode *sqsh_ino = &squashfs_ino.dev;
unsigned int rdev;
err = squashfs_read_metadata(sb, sqsh_ino, &block, &offset,
sizeof(*sqsh_ino));
if (err < 0)
goto failed_read;
if (type == SQUASHFS_CHRDEV_TYPE)
inode->i_mode |= S_IFCHR;
else
inode->i_mode |= S_IFBLK;
set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
rdev = le32_to_cpu(sqsh_ino->rdev);
init_special_inode(inode, inode->i_mode, new_decode_dev(rdev));
TRACE("Device inode %x:%x, rdev %x\n",
SQUASHFS_INODE_BLK(ino), offset, rdev);
break;
}
case SQUASHFS_LBLKDEV_TYPE:
case SQUASHFS_LCHRDEV_TYPE: {
struct squashfs_ldev_inode *sqsh_ino = &squashfs_ino.ldev;
unsigned int rdev;
err = squashfs_read_metadata(sb, sqsh_ino, &block, &offset,
sizeof(*sqsh_ino));
if (err < 0)
goto failed_read;
if (type == SQUASHFS_LCHRDEV_TYPE)
inode->i_mode |= S_IFCHR;
else
inode->i_mode |= S_IFBLK;
xattr_id = le32_to_cpu(sqsh_ino->xattr);
inode->i_op = &squashfs_inode_ops;
set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
rdev = le32_to_cpu(sqsh_ino->rdev);
init_special_inode(inode, inode->i_mode, new_decode_dev(rdev));
TRACE("Device inode %x:%x, rdev %x\n",
SQUASHFS_INODE_BLK(ino), offset, rdev);
break;
}
case SQUASHFS_FIFO_TYPE:
case SQUASHFS_SOCKET_TYPE: {
struct squashfs_ipc_inode *sqsh_ino = &squashfs_ino.ipc;
err = squashfs_read_metadata(sb, sqsh_ino, &block, &offset,
sizeof(*sqsh_ino));
if (err < 0)
goto failed_read;
if (type == SQUASHFS_FIFO_TYPE)
inode->i_mode |= S_IFIFO;
else
inode->i_mode |= S_IFSOCK;
set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
init_special_inode(inode, inode->i_mode, 0);
break;
}
case SQUASHFS_LFIFO_TYPE:
case SQUASHFS_LSOCKET_TYPE: {
struct squashfs_lipc_inode *sqsh_ino = &squashfs_ino.lipc;
err = squashfs_read_metadata(sb, sqsh_ino, &block, &offset,
sizeof(*sqsh_ino));
if (err < 0)
goto failed_read;
if (type == SQUASHFS_LFIFO_TYPE)
inode->i_mode |= S_IFIFO;
else
inode->i_mode |= S_IFSOCK;
xattr_id = le32_to_cpu(sqsh_ino->xattr);
inode->i_op = &squashfs_inode_ops;
set_nlink(inode, le32_to_cpu(sqsh_ino->nlink));
init_special_inode(inode, inode->i_mode, 0);
break;
}
default:
ERROR("Unknown inode type %d in squashfs_iget!\n", type);
return -EINVAL;
}
if (xattr_id != SQUASHFS_INVALID_XATTR && msblk->xattr_id_table) {
err = squashfs_xattr_lookup(sb, xattr_id,
&squashfs_i(inode)->xattr_count,
&squashfs_i(inode)->xattr_size,
&squashfs_i(inode)->xattr);
if (err < 0)
goto failed_read;
inode->i_blocks += ((squashfs_i(inode)->xattr_size - 1) >> 9)
+ 1;
} else
squashfs_i(inode)->xattr_count = 0;
return 0;
failed_read:
ERROR("Unable to read inode 0x%llx\n", ino);
return err;
}
const struct inode_operations squashfs_inode_ops = {
.listxattr = squashfs_listxattr
};
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