Commit d95efb14 authored by Jeremy Bongio's avatar Jeremy Bongio Committed by Theodore Ts'o
Browse files

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



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

Reviewed-by: default avatarTheodore Ts'o <tytso@mit.edu>
Signed-off-by: default avatarJeremy Bongio <bongiojp@gmail.com>
Link: https://lore.kernel.org/r/20220721224422.438351-1-bongiojp@gmail.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 69cb8e9d

fs/ext4/ext4.h

+11 −0
Original line number Diff line number Diff line
@@ -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

fs/ext4/ioctl.c

+83 −0
Original line number Diff line number Diff line
@@ -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 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 
		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;