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ext4: implementation of a new ioctl called EXT4_IOC_SWAP_BOOT 

Add a new ioctl, EXT4_IOC_SWAP_BOOT which swaps i_blocks and
associated attributes (like i_blocks, i_size, i_flags, ...) from the
specified inode with inode EXT4_BOOT_LOADER_INO (#5). This is
typically used to store a boot loader in a secure part of the
filesystem, where it can't be changed by a normal user by accident.
The data blocks of the previous boot loader will be associated with
the given inode.

This usercode program is a simple example of the usage:

int main(int argc, char *argv[])
{
  int fd;
  int err;

  if ( argc != 2 ) {
    printf("usage: ext4-swap-boot-inode FILE-TO-SWAP\n");
    exit(1);
  }

  fd = open(argv[1], O_WRONLY);
  if ( fd < 0 ) {
    perror("open");
    exit(1);
  }

  err = ioctl(fd, EXT4_IOC_SWAP_BOOT);
  if ( err < 0 ) {
    perror("ioctl");
    exit(1);
  }

  close(fd);
  exit(0);
}

[ Modified by Theodore Ts'o to fix a number of bugs in the original code.]

Signed-off-by: Dr. Tilmann Bubeck <t.bubeck@reinform.de>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Dr. Tilmann Bubeck 2013-04-08 12:54:05 -04:00 committed by Theodore Ts'o
parent f78ee70db4
commit 393d1d1d76
5 changed files with 248 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
Documentation/filesystems/ext4.txt
View File

@ -587,6 +587,16 @@ Table of Ext4 specific ioctls
bitmaps and inode table, the userspace tool thus
just passes the new number of blocks.
EXT4_IOC_SWAP_BOOT Swap i_blocks and associated attributes
(like i_blocks, i_size, i_flags, ...) from
the specified inode with inode
EXT4_BOOT_LOADER_INO (#5). This is typically
used to store a boot loader in a secure part of
the filesystem, where it can't be changed by a
normal user by accident.
The data blocks of the previous boot loader
will be associated with the given inode.
..............................................................................
References

8
fs/ext4/ext4.h
View File

@ -616,6 +616,7 @@ enum {
#define EXT4_IOC_ALLOC_DA_BLKS _IO('f', 12)
#define EXT4_IOC_MOVE_EXT _IOWR('f', 15, struct move_extent)
#define EXT4_IOC_RESIZE_FS _IOW('f', 16, __u64)
#define EXT4_IOC_SWAP_BOOT _IO('f', 17)
#if defined(__KERNEL__) && defined(CONFIG_COMPAT)
/*
@ -1341,6 +1342,7 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino)
return ino == EXT4_ROOT_INO ||
ino == EXT4_USR_QUOTA_INO ||
ino == EXT4_GRP_QUOTA_INO ||
ino == EXT4_BOOT_LOADER_INO ||
ino == EXT4_JOURNAL_INO ||
ino == EXT4_RESIZE_INO ||
(ino >= EXT4_FIRST_INO(sb) &&
@ -2624,6 +2626,12 @@ extern int ext4_ind_migrate(struct inode *inode);
/* move_extent.c */
extern void ext4_double_down_write_data_sem(struct inode *first,
struct inode *second);
extern void ext4_double_up_write_data_sem(struct inode *orig_inode,
struct inode *donor_inode);
void ext4_inode_double_lock(struct inode *inode1, struct inode *inode2);
void ext4_inode_double_unlock(struct inode *inode1, struct inode *inode2);
extern int ext4_move_extents(struct file *o_filp, struct file *d_filp,
__u64 start_orig, __u64 start_donor,
__u64 len, __u64 *moved_len);

11
fs/ext4/inode.c
View File

@ -4191,8 +4191,9 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
* NeilBrown 1999oct15
*/
if (inode->i_nlink == 0) {
if (inode->i_mode == 0 ||
!(EXT4_SB(inode->i_sb)->s_mount_state & EXT4_ORPHAN_FS)) {
if ((inode->i_mode == 0 ||
!(EXT4_SB(inode->i_sb)->s_mount_state & EXT4_ORPHAN_FS)) &&
ino != EXT4_BOOT_LOADER_INO) {
/* this inode is deleted */
ret = -ESTALE;
goto bad_inode;
@ -4200,7 +4201,9 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
/* The only unlinked inodes we let through here have
* valid i_mode and are being read by the orphan
* recovery code: that's fine, we're about to complete
* the process of deleting those. */
* the process of deleting those.
* OR it is the EXT4_BOOT_LOADER_INO which is
* not initialized on a new filesystem. */
}
ei->i_flags = le32_to_cpu(raw_inode->i_flags);
inode->i_blocks = ext4_inode_blocks(raw_inode, ei);
@ -4320,6 +4323,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
else
init_special_inode(inode, inode->i_mode,
new_decode_dev(le32_to_cpu(raw_inode->i_block[1])));
} else if (ino == EXT4_BOOT_LOADER_INO) {
make_bad_inode(inode);
} else {
ret = -EIO;
EXT4_ERROR_INODE(inode, "bogus i_mode (%o)", inode->i_mode);

197
fs/ext4/ioctl.c
View File

@ -17,9 +17,201 @@
#include <asm/uaccess.h>
#include "ext4_jbd2.h"
#include "ext4.h"
#include "ext4_extents.h"
#define MAX_32_NUM ((((unsigned long long) 1) << 32) - 1)
/**
* Swap memory between @a and @b for @len bytes.
*
* @a: pointer to first memory area
* @b: pointer to second memory area
* @len: number of bytes to swap
*
*/
static void memswap(void *a, void *b, size_t len)
{
unsigned char *ap, *bp;
unsigned char tmp;
ap = (unsigned char *)a;
bp = (unsigned char *)b;
while (len-- > 0) {
tmp = *ap;
*ap = *bp;
*bp = tmp;
ap++;
bp++;
}
}
/**
* Swap i_data and associated attributes between @inode1 and @inode2.
* This function is used for the primary swap between inode1 and inode2
* and also to revert this primary swap in case of errors.
*
* Therefore you have to make sure, that calling this method twice
* will revert all changes.
*
* @inode1: pointer to first inode
* @inode2: pointer to second inode
*/
static void swap_inode_data(struct inode *inode1, struct inode *inode2)
{
loff_t isize;
struct ext4_inode_info *ei1;
struct ext4_inode_info *ei2;
ei1 = EXT4_I(inode1);
ei2 = EXT4_I(inode2);
memswap(&inode1->i_flags, &inode2->i_flags, sizeof(inode1->i_flags));
memswap(&inode1->i_version, &inode2->i_version,
sizeof(inode1->i_version));
memswap(&inode1->i_blocks, &inode2->i_blocks,
sizeof(inode1->i_blocks));
memswap(&inode1->i_bytes, &inode2->i_bytes, sizeof(inode1->i_bytes));
memswap(&inode1->i_atime, &inode2->i_atime, sizeof(inode1->i_atime));
memswap(&inode1->i_mtime, &inode2->i_mtime, sizeof(inode1->i_mtime));
memswap(ei1->i_data, ei2->i_data, sizeof(ei1->i_data));
memswap(&ei1->i_flags, &ei2->i_flags, sizeof(ei1->i_flags));
memswap(&ei1->i_disksize, &ei2->i_disksize, sizeof(ei1->i_disksize));
memswap(&ei1->i_es_tree, &ei2->i_es_tree, sizeof(ei1->i_es_tree));
memswap(&ei1->i_es_lru_nr, &ei2->i_es_lru_nr, sizeof(ei1->i_es_lru_nr));
isize = i_size_read(inode1);
i_size_write(inode1, i_size_read(inode2));
i_size_write(inode2, isize);
}
/**
* Swap the information from the given @inode and the inode
* EXT4_BOOT_LOADER_INO. It will basically swap i_data and all other
* important fields of the inodes.
*
* @sb: the super block of the filesystem
* @inode: the inode to swap with EXT4_BOOT_LOADER_INO
*
*/
static long swap_inode_boot_loader(struct super_block *sb,
struct inode *inode)
{
handle_t *handle;
int err;
struct inode *inode_bl;
struct ext4_inode_info *ei;
struct ext4_inode_info *ei_bl;
struct ext4_sb_info *sbi;
if (inode->i_nlink != 1 || !S_ISREG(inode->i_mode)) {
err = -EINVAL;
goto swap_boot_out;
}
if (!inode_owner_or_capable(inode) || !capable(CAP_SYS_ADMIN)) {
err = -EPERM;
goto swap_boot_out;
}
sbi = EXT4_SB(sb);
ei = EXT4_I(inode);
inode_bl = ext4_iget(sb, EXT4_BOOT_LOADER_INO);
if (IS_ERR(inode_bl)) {
err = PTR_ERR(inode_bl);
goto swap_boot_out;
}
ei_bl = EXT4_I(inode_bl);
filemap_flush(inode->i_mapping);
filemap_flush(inode_bl->i_mapping);
/* Protect orig inodes against a truncate and make sure,
* that only 1 swap_inode_boot_loader is running. */
ext4_inode_double_lock(inode, inode_bl);
truncate_inode_pages(&inode->i_data, 0);
truncate_inode_pages(&inode_bl->i_data, 0);
/* Wait for all existing dio workers */
ext4_inode_block_unlocked_dio(inode);
ext4_inode_block_unlocked_dio(inode_bl);
inode_dio_wait(inode);
inode_dio_wait(inode_bl);
handle = ext4_journal_start(inode_bl, EXT4_HT_MOVE_EXTENTS, 2);
if (IS_ERR(handle)) {
err = -EINVAL;
goto swap_boot_out;
}
/* Protect extent tree against block allocations via delalloc */
ext4_double_down_write_data_sem(inode, inode_bl);
if (inode_bl->i_nlink == 0) {
/* this inode has never been used as a BOOT_LOADER */
set_nlink(inode_bl, 1);
i_uid_write(inode_bl, 0);
i_gid_write(inode_bl, 0);
inode_bl->i_flags = 0;
ei_bl->i_flags = 0;
inode_bl->i_version = 1;
i_size_write(inode_bl, 0);
inode_bl->i_mode = S_IFREG;
if (EXT4_HAS_INCOMPAT_FEATURE(sb,
EXT4_FEATURE_INCOMPAT_EXTENTS)) {
ext4_set_inode_flag(inode_bl, EXT4_INODE_EXTENTS);
ext4_ext_tree_init(handle, inode_bl);
} else
memset(ei_bl->i_data, 0, sizeof(ei_bl->i_data));
}
swap_inode_data(inode, inode_bl);
inode->i_ctime = inode_bl->i_ctime = ext4_current_time(inode);
spin_lock(&sbi->s_next_gen_lock);
inode->i_generation = sbi->s_next_generation++;
inode_bl->i_generation = sbi->s_next_generation++;
spin_unlock(&sbi->s_next_gen_lock);
ext4_discard_preallocations(inode);
err = ext4_mark_inode_dirty(handle, inode);
if (err < 0) {
ext4_warning(inode->i_sb,
"couldn't mark inode #%lu dirty (err %d)",
inode->i_ino, err);
/* Revert all changes: */
swap_inode_data(inode, inode_bl);
} else {
err = ext4_mark_inode_dirty(handle, inode_bl);
if (err < 0) {
ext4_warning(inode_bl->i_sb,
"couldn't mark inode #%lu dirty (err %d)",
inode_bl->i_ino, err);
/* Revert all changes: */
swap_inode_data(inode, inode_bl);
ext4_mark_inode_dirty(handle, inode);
}
}
ext4_journal_stop(handle);
ext4_double_up_write_data_sem(inode, inode_bl);
ext4_inode_resume_unlocked_dio(inode);
ext4_inode_resume_unlocked_dio(inode_bl);
ext4_inode_double_unlock(inode, inode_bl);
iput(inode_bl);
swap_boot_out:
return err;
}
long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
struct inode *inode = file_inode(filp);
@ -353,6 +545,11 @@ group_add_out:
return err;
}
case EXT4_IOC_SWAP_BOOT:
if (!(filp->f_mode & FMODE_WRITE))
return -EBADF;
return swap_inode_boot_loader(sb, inode);
case EXT4_IOC_RESIZE_FS: {
ext4_fsblk_t n_blocks_count;
struct super_block *sb = inode->i_sb;

48
fs/ext4/move_extent.c
View File

@ -144,12 +144,13 @@ mext_next_extent(struct inode *inode, struct ext4_ext_path *path,
}
/**
* double_down_write_data_sem - Acquire two inodes' write lock of i_data_sem
* ext4_double_down_write_data_sem - Acquire two inodes' write lock
* of i_data_sem
*
* Acquire write lock of i_data_sem of the two inodes
*/
static void
double_down_write_data_sem(struct inode *first, struct inode *second)
void
ext4_double_down_write_data_sem(struct inode *first, struct inode *second)
{
if (first < second) {
down_write(&EXT4_I(first)->i_data_sem);
@ -162,14 +163,15 @@ double_down_write_data_sem(struct inode *first, struct inode *second)
}
/**
* double_up_write_data_sem - Release two inodes' write lock of i_data_sem
* ext4_double_up_write_data_sem - Release two inodes' write lock of i_data_sem
*
* @orig_inode: original inode structure to be released its lock first
* @donor_inode: donor inode structure to be released its lock second
* Release write lock of i_data_sem of two inodes (orig and donor).
*/
static void
double_up_write_data_sem(struct inode *orig_inode, struct inode *donor_inode)
void
ext4_double_up_write_data_sem(struct inode *orig_inode,
struct inode *donor_inode)
{
up_write(&EXT4_I(orig_inode)->i_data_sem);
up_write(&EXT4_I(donor_inode)->i_data_sem);
@ -976,7 +978,7 @@ again:
* necessary, just swap data blocks between orig and donor.
*/
if (uninit) {
double_down_write_data_sem(orig_inode, donor_inode);
ext4_double_down_write_data_sem(orig_inode, donor_inode);
/* If any of extents in range became initialized we have to
* fallback to data copying */
uninit = mext_check_coverage(orig_inode, orig_blk_offset,
@ -990,7 +992,7 @@ again:
goto drop_data_sem;
if (!uninit) {
double_up_write_data_sem(orig_inode, donor_inode);
ext4_double_up_write_data_sem(orig_inode, donor_inode);
goto data_copy;
}
if ((page_has_private(pagep[0]) &&
@ -1004,7 +1006,7 @@ again:
donor_inode, orig_blk_offset,
block_len_in_page, err);
drop_data_sem:
double_up_write_data_sem(orig_inode, donor_inode);
ext4_double_up_write_data_sem(orig_inode, donor_inode);
goto unlock_pages;
}
data_copy:
@ -1065,11 +1067,11 @@ repair_branches:
* Extents are swapped already, but we are not able to copy data.
* Try to swap extents to it's original places
*/
double_down_write_data_sem(orig_inode, donor_inode);
ext4_double_down_write_data_sem(orig_inode, donor_inode);
replaced_count = mext_replace_branches(handle, donor_inode, orig_inode,
orig_blk_offset,
block_len_in_page, &err2);
double_up_write_data_sem(orig_inode, donor_inode);
ext4_double_up_write_data_sem(orig_inode, donor_inode);
if (replaced_count != block_len_in_page) {
EXT4_ERROR_INODE_BLOCK(orig_inode, (sector_t)(orig_blk_offset),
"Unable to copy data block,"
@ -1209,15 +1211,15 @@ mext_check_arguments(struct inode *orig_inode,
}
/**
* mext_inode_double_lock - Lock i_mutex on both @inode1 and @inode2
* ext4_inode_double_lock - Lock i_mutex on both @inode1 and @inode2
*
* @inode1: the inode structure
* @inode2: the inode structure
*
* Lock two inodes' i_mutex
*/
static void
mext_inode_double_lock(struct inode *inode1, struct inode *inode2)
void
ext4_inode_double_lock(struct inode *inode1, struct inode *inode2)
{
BUG_ON(inode1 == inode2);
if (inode1 < inode2) {
@ -1230,15 +1232,15 @@ mext_inode_double_lock(struct inode *inode1, struct inode *inode2)
}
/**
* mext_inode_double_unlock - Release i_mutex on both @inode1 and @inode2
* ext4_inode_double_unlock - Release i_mutex on both @inode1 and @inode2
*
* @inode1: the inode that is released first
* @inode2: the inode that is released second
*
*/
static void
mext_inode_double_unlock(struct inode *inode1, struct inode *inode2)
void
ext4_inode_double_unlock(struct inode *inode1, struct inode *inode2)
{
mutex_unlock(&inode1->i_mutex);
mutex_unlock(&inode2->i_mutex);
@ -1333,7 +1335,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
return -EINVAL;
}
/* Protect orig and donor inodes against a truncate */
mext_inode_double_lock(orig_inode, donor_inode);
ext4_inode_double_lock(orig_inode, donor_inode);
/* Wait for all existing dio workers */
ext4_inode_block_unlocked_dio(orig_inode);
@ -1342,7 +1344,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
inode_dio_wait(donor_inode);
/* Protect extent tree against block allocations via delalloc */
double_down_write_data_sem(orig_inode, donor_inode);
ext4_double_down_write_data_sem(orig_inode, donor_inode);
/* Check the filesystem environment whether move_extent can be done */
ret = mext_check_arguments(orig_inode, donor_inode, orig_start,
donor_start, &len);
@ -1466,7 +1468,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
* b. racing with ->readpage, ->write_begin, and ext4_get_block
* in move_extent_per_page
*/
double_up_write_data_sem(orig_inode, donor_inode);
ext4_double_up_write_data_sem(orig_inode, donor_inode);
while (orig_page_offset <= seq_end_page) {
@ -1500,7 +1502,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
block_len_in_page = rest_blocks;
}
double_down_write_data_sem(orig_inode, donor_inode);
ext4_double_down_write_data_sem(orig_inode, donor_inode);
if (ret < 0)
break;
@ -1538,10 +1540,10 @@ out:
ext4_ext_drop_refs(holecheck_path);
kfree(holecheck_path);
}
double_up_write_data_sem(orig_inode, donor_inode);
ext4_double_up_write_data_sem(orig_inode, donor_inode);
ext4_inode_resume_unlocked_dio(orig_inode);
ext4_inode_resume_unlocked_dio(donor_inode);
mext_inode_double_unlock(orig_inode, donor_inode);
ext4_inode_double_unlock(orig_inode, donor_inode);
return ret;
}