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[104.173.199.31]) by smtp.googlemail.com with ESMTPSA id pj5-20020a17090b4f4500b001df264610c4sm9925763pjb.0.2022.07.21.15.44.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Jul 2022 15:44:30 -0700 (PDT) From: Jeremy Bongio To: Ted Tso Cc: linux-ext4@vger.kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, Jeremy Bongio Subject: [PATCH v5] Add ioctls to get/set the ext4 superblock uuid. Date: Thu, 21 Jul 2022 15:44:22 -0700 Message-Id: <20220721224422.438351-1-bongiojp@gmail.com> X-Mailer: git-send-email 2.37.1.359.gd136c6c3e2-goog MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org This fixes a race between changing the ext4 superblock uuid and operations like mounting, resizing, changing features, etc. Reviewed-by: Theodore Ts'o Signed-off-by: Jeremy Bongio Reviewed-by: Darrick J. Wong --- 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 #include #include +#include #include "ext4_jbd2.h" #include "ext4.h" #include @@ -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;