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ext4: add ioctls to get/set the ext4 superblock uuid

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This fixes a race between changing the ext4 superblock uuid and operations
like mounting, resizing, changing features, etc.

Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jeremy Bongio <bongiojp@gmail.com>
Link: https://lore.kernel.org/r/20220721224422.438351-1-bongiojp@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Jeremy Bongio 2022-07-21 15:44:22 -07:00 committed by Theodore Ts'o
parent 69cb8e9d8c
commit d95efb14c0
2 changed files with 94 additions and 0 deletions
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11
fs/ext4/ext4.h
View File

@ -724,6 +724,8 @@ enum {
#define EXT4_IOC_GETSTATE _IOW('f', 41, __u32)
#define EXT4_IOC_GET_ES_CACHE _IOWR('f', 42, struct fiemap)
#define EXT4_IOC_CHECKPOINT _IOW('f', 43, __u32)
#define EXT4_IOC_GETFSUUID _IOR('f', 44, struct fsuuid)
#define EXT4_IOC_SETFSUUID _IOW('f', 44, struct fsuuid)
#define EXT4_IOC_SHUTDOWN _IOR ('X', 125, __u32)
@ -753,6 +755,15 @@ enum {
EXT4_IOC_CHECKPOINT_FLAG_ZEROOUT | \
EXT4_IOC_CHECKPOINT_FLAG_DRY_RUN)
/*
* Structure for EXT4_IOC_GETFSUUID/EXT4_IOC_SETFSUUID
*/
struct fsuuid {
__u32 fsu_len;
__u32 fsu_flags;
__u8 fsu_uuid[];
};
#if defined(__KERNEL__) && defined(CONFIG_COMPAT)
/*
* ioctl commands in 32 bit emulation

83
fs/ext4/ioctl.c
View File

@ -20,6 +20,7 @@
#include <linux/delay.h>
#include <linux/iversion.h>
#include <linux/fileattr.h>
#include <linux/uuid.h>
#include "ext4_jbd2.h"
#include "ext4.h"
#include <linux/fsmap.h>
@ -41,6 +42,15 @@ static void ext4_sb_setlabel(struct ext4_super_block *es, const void *arg)
memcpy(es->s_volume_name, (char *)arg, EXT4_LABEL_MAX);
}
/*
* Superblock modification callback function for changing file system
* UUID.
*/
static void ext4_sb_setuuid(struct ext4_super_block *es, const void *arg)
{
memcpy(es->s_uuid, (__u8 *)arg, UUID_SIZE);
}
static
int ext4_update_primary_sb(struct super_block *sb, handle_t *handle,
ext4_update_sb_callback func,
@ -1133,6 +1143,73 @@ static int ext4_ioctl_getlabel(struct ext4_sb_info *sbi, char __user *user_label
return 0;
}
static int ext4_ioctl_getuuid(struct ext4_sb_info *sbi,
struct fsuuid __user *ufsuuid)
{
struct fsuuid fsuuid;
__u8 uuid[UUID_SIZE];
if (copy_from_user(&fsuuid, ufsuuid, sizeof(fsuuid)))
return -EFAULT;
if (fsuuid.fsu_len == 0) {
fsuuid.fsu_len = UUID_SIZE;
if (copy_to_user(ufsuuid, &fsuuid, sizeof(fsuuid.fsu_len)))
return -EFAULT;
return -EINVAL;
}
if (fsuuid.fsu_len != UUID_SIZE || fsuuid.fsu_flags != 0)
return -EINVAL;
lock_buffer(sbi->s_sbh);
memcpy(uuid, sbi->s_es->s_uuid, UUID_SIZE);
unlock_buffer(sbi->s_sbh);
if (copy_to_user(&ufsuuid->fsu_uuid[0], uuid, UUID_SIZE))
return -EFAULT;
return 0;
}
static int ext4_ioctl_setuuid(struct file *filp,
const struct fsuuid __user *ufsuuid)
{
int ret = 0;
struct super_block *sb = file_inode(filp)->i_sb;
struct fsuuid fsuuid;
__u8 uuid[UUID_SIZE];
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
/*
* If any checksums (group descriptors or metadata) are being used
* then the checksum seed feature is required to change the UUID.
*/
if (((ext4_has_feature_gdt_csum(sb) || ext4_has_metadata_csum(sb))
&& !ext4_has_feature_csum_seed(sb))
|| ext4_has_feature_stable_inodes(sb))
return -EOPNOTSUPP;
if (copy_from_user(&fsuuid, ufsuuid, sizeof(fsuuid)))
return -EFAULT;
if (fsuuid.fsu_len != UUID_SIZE || fsuuid.fsu_flags != 0)
return -EINVAL;
if (copy_from_user(uuid, &ufsuuid->fsu_uuid[0], UUID_SIZE))
return -EFAULT;
ret = mnt_want_write_file(filp);
if (ret)
return ret;
ret = ext4_update_superblocks_fn(sb, ext4_sb_setuuid, &uuid);
mnt_drop_write_file(filp);
return ret;
}
static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
struct inode *inode = file_inode(filp);
@ -1515,6 +1592,10 @@ resizefs_out:
return ext4_ioctl_setlabel(filp,
(const void __user *)arg);
case EXT4_IOC_GETFSUUID:
return ext4_ioctl_getuuid(EXT4_SB(sb), (void __user *)arg);
case EXT4_IOC_SETFSUUID:
return ext4_ioctl_setuuid(filp, (const void __user *)arg);
default:
return -ENOTTY;
}
@ -1592,6 +1673,8 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
case EXT4_IOC_CHECKPOINT:
case FS_IOC_GETFSLABEL:
case FS_IOC_SETFSLABEL:
case EXT4_IOC_GETFSUUID:
case EXT4_IOC_SETFSUUID:
break;
default:
return -ENOIOCTLCMD;