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Date: Tue, 19 Jul 2022 16:52:04 -0700 Message-Id: <20220719235204.237526-1-bongiojp@gmail.com> X-Mailer: git-send-email 2.37.0.170.g444d1eabd0-goog MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org When mounted, there is a race condition between changing the filesystem UUID and changing other aspects of the filesystem, like mounting, resizing, changing features, etc. Using these ioctls to get/set the UUID ensures the filesystem is not being resized. Signed-off-by: Jeremy Bongio --- Changes in V3: Added modified utility to commit heading. Simplified return value of handle_fsuuid. Added get_mounted_fsuuid and set_mounted_fsuuid for clarity. misc/tune2fs.c | 113 +++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 95 insertions(+), 18 deletions(-) diff --git a/misc/tune2fs.c b/misc/tune2fs.c index 6c162ba5..36863acf 100644 --- a/misc/tune2fs.c +++ b/misc/tune2fs.c @@ -82,11 +82,25 @@ extern int optind; #define FS_IOC_GETFSLABEL _IOR(0x94, 49, char[FSLABEL_MAX]) #endif +struct fsuuid { + __u32 fsu_len; + __u32 fsu_flags; + __u8 fsu_uuid[]; +}; + +#ifndef EXT4_IOC_GETFSUUID +#define EXT4_IOC_GETFSUUID _IOR('f', 44, struct fsuuid) +#endif + +#ifndef EXT4_IOC_SETFSUUID +#define EXT4_IOC_SETFSUUID _IOW('f', 44, struct fsuuid) +#endif + extern int ask_yn(const char *string, int def); const char *program_name = "tune2fs"; char *device_name; -char *new_label, *new_last_mounted, *new_UUID; +char *new_label, *new_last_mounted, *requested_uuid; char *io_options; static int c_flag, C_flag, e_flag, f_flag, g_flag, i_flag, l_flag, L_flag; static int m_flag, M_flag, Q_flag, r_flag, s_flag = -1, u_flag, U_flag, T_flag; @@ -2102,7 +2116,7 @@ static void parse_tune2fs_options(int argc, char **argv) open_flag = EXT2_FLAG_RW; break; case 'U': - new_UUID = optarg; + requested_uuid = optarg; U_flag = 1; open_flag = EXT2_FLAG_RW | EXT2_FLAG_JOURNAL_DEV_OK; @@ -3078,6 +3092,61 @@ int handle_fslabel(int setlabel) { return 0; } +/* + * Use EXT4_IOC_GETFSUUID/EXT4_IOC_SETFSUUID to get/set file system UUID. + * Return: 0 on success + * -1 when the old method should be used + */ +int handle_fsuuid(__u8 *uuid, bool get) +{ + errcode_t ret; + int mnt_flags, fd; + char label[FSLABEL_MAX]; + int maxlen = FSLABEL_MAX - 1; + char mntpt[PATH_MAX + 1]; + struct fsuuid *fsuuid = NULL; + + fsuuid = malloc(sizeof(*fsuuid) + UUID_SIZE); + if (!fsuuid) + return -1; + + memcpy(fsuuid->fsu_uuid, uuid, UUID_SIZE); + fsuuid->fsu_len = UUID_SIZE; + fsuuid->fsu_flags = 0; + + ret = ext2fs_check_mount_point(device_name, &mnt_flags, + mntpt, sizeof(mntpt)); + if (ret || !(mnt_flags & EXT2_MF_MOUNTED) || + (!get && (mnt_flags & EXT2_MF_READONLY)) || + !mntpt[0]) + return -1; + + fd = open(mntpt, O_RDONLY); + if (fd < 0) + return -1; + + if (get) + ret = ioctl(fd, EXT4_IOC_GETFSUUID, fsuuid); + else + ret = ioctl(fd, EXT4_IOC_SETFSUUID, fsuuid); + + close(fd); + if (ret) + return -1; + return 0; +} + +static inline int get_mounted_fsuuid(__u8 *old_uuid) +{ + return handle_fsuuid(old_uuid, true); +} + +static inline int set_mounted_fsuuid(__u8 *new_uuid) +{ + return handle_fsuuid(new_uuid, false); +} + + #ifndef BUILD_AS_LIB int main(int argc, char **argv) #else @@ -3454,6 +3523,7 @@ _("Warning: The journal is dirty. You may wish to replay the journal like:\n\n" dgrp_t i; char buf[SUPERBLOCK_SIZE] __attribute__ ((aligned(8))); __u8 old_uuid[UUID_SIZE]; + uuid_t new_uuid; if (ext2fs_has_feature_stable_inodes(fs->super)) { fputs(_("Cannot change the UUID of this filesystem " @@ -3507,25 +3577,34 @@ _("Warning: The journal is dirty. You may wish to replay the journal like:\n\n" set_csum = 1; } - memcpy(old_uuid, sb->s_uuid, UUID_SIZE); - if ((strcasecmp(new_UUID, "null") == 0) || - (strcasecmp(new_UUID, "clear") == 0)) { - uuid_clear(sb->s_uuid); - } else if (strcasecmp(new_UUID, "time") == 0) { - uuid_generate_time(sb->s_uuid); - } else if (strcasecmp(new_UUID, "random") == 0) { - uuid_generate(sb->s_uuid); - } else if (uuid_parse(new_UUID, sb->s_uuid)) { + rc = get_mounted_fsuuid(old_uuid); + if (rc == -1) + memcpy(old_uuid, sb->s_uuid, UUID_SIZE); + + if ((strcasecmp(requested_uuid, "null") == 0) || + (strcasecmp(requested_uuid, "clear") == 0)) { + uuid_clear(new_uuid); + } else if (strcasecmp(requested_uuid, "time") == 0) { + uuid_generate_time(new_uuid); + } else if (strcasecmp(requested_uuid, "random") == 0) { + uuid_generate(new_uuid); + } else if (uuid_parse(requested_uuid, new_uuid)) { com_err(program_name, 0, "%s", _("Invalid UUID format\n")); rc = 1; goto closefs; } - ext2fs_init_csum_seed(fs); - if (set_csum) { - for (i = 0; i < fs->group_desc_count; i++) - ext2fs_group_desc_csum_set(fs, i); - fs->flags &= ~EXT2_FLAG_SUPER_ONLY; + + rc = set_mounted_fsuuid(new_uuid); + if (rc == -1) { + memcpy(sb->s_uuid, new_uuid, UUID_SIZE); + ext2fs_init_csum_seed(fs); + if (set_csum) { + for (i = 0; i < fs->group_desc_count; i++) + ext2fs_group_desc_csum_set(fs, i); + fs->flags &= ~EXT2_FLAG_SUPER_ONLY; + } + ext2fs_mark_super_dirty(fs); } /* If this is a journal dev, we need to copy UUID into jsb */ @@ -3549,8 +3628,6 @@ _("Warning: The journal is dirty. You may wish to replay the journal like:\n\n" if ((rc = fs_update_journal_user(sb, old_uuid))) goto closefs; } - - ext2fs_mark_super_dirty(fs); } if (I_flag) {