diff mbox series

[v5] Add ioctls to get/set the ext4 superblock uuid.

Message ID 20220721224422.438351-1-bongiojp@gmail.com (mailing list archive)
State New, archived
Headers show
Series [v5] Add ioctls to get/set the ext4 superblock uuid. | expand

Commit Message

Jeremy Bongio July 21, 2022, 10:44 p.m. UTC 
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>
---

Changes in v5:

Return size of uuid in a EXT4_IOC_GETFSUUID operation if fsu_len is 0.

 fs/ext4/ext4.h  | 11 +++++++
 fs/ext4/ioctl.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 94 insertions(+)

Comments

Theodore Ts'o July 22, 2022, 1:58 p.m. UTC | #1 
On Thu, 21 Jul 2022 15:44:22 -0700, Jeremy Bongio wrote:
> This fixes a race between changing the ext4 superblock uuid and operations
> like mounting, resizing, changing features, etc.
> 
> 

Applied, thanks!

[1/1] Add ioctls to get/set the ext4 superblock uuid.
      commit: 2cdc09d757bf2cefe5de132076eb5d0a8e8df384

Best regards,
Darrick J. Wong July 22, 2022, 5:19 p.m. UTC | #2 
On Thu, Jul 21, 2022 at 03:44:22PM -0700, Jeremy Bongio wrote:
> 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>

It's possibly too late for this, but:
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> Signed-off-by: Jeremy Bongio <bongiojp@gmail.com>
> ---
> 
> Changes in v5:
> 
> Return size of uuid in a EXT4_IOC_GETFSUUID operation if fsu_len is 0.
> 
>  fs/ext4/ext4.h  | 11 +++++++
>  fs/ext4/ioctl.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 94 insertions(+)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 75b8d81b2469..b760d669a1ca 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -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
> diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
> index cb01c1da0f9d..b7c9bf9e7864 100644
> --- a/fs/ext4/ioctl.c
> +++ b/fs/ext4/ioctl.c
> @@ -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,
> @@ -1131,6 +1141,73 @@ 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);
> @@ -1509,6 +1586,10 @@ 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;
>  	}
> @@ -1586,6 +1667,8 @@ 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;
> -- 
> 2.37.1.359.gd136c6c3e2-goog
>
diff mbox series

Patch

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 75b8d81b2469..b760d669a1ca 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -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
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index cb01c1da0f9d..b7c9bf9e7864 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -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,
@@ -1131,6 +1141,73 @@  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);
@@ -1509,6 +1586,10 @@  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;
 	}
@@ -1586,6 +1667,8 @@  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;