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 <bongiojp@xxxxxxxxx> --- Changes in v4: Ioctl calls are now inline. handle_fsuuid() is removed. Fsuuid is freed. ext2fs_check_if_mounted() call replaced with ext2fs_check_mount_point() to avoid redundancy. I tested mounted and unmounted code paths. misc/tune2fs.c | 98 ++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 79 insertions(+), 19 deletions(-) diff --git a/misc/tune2fs.c b/misc/tune2fs.c index 6c162ba5..d0cb90ae 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; @@ -3090,6 +3104,7 @@ int tune2fs_main(int argc, char **argv) io_manager io_ptr, io_ptr_orig = NULL; int rc = 0; char default_undo_file[1] = { 0 }; + char mntpt[PATH_MAX + 1]; #ifdef ENABLE_NLS setlocale(LC_MESSAGES, ""); @@ -3237,9 +3252,10 @@ retry_open: goto closefs; } - retval = ext2fs_check_if_mounted(device_name, &mount_flags); + retval = ext2fs_check_mount_point(device_name, &mount_flags, + mntpt, sizeof(mntpt)); if (retval) { - com_err("ext2fs_check_if_mount", retval, + com_err("ext2fs_check_mount_point", retval, _("while determining whether %s is mounted."), device_name); rc = 1; @@ -3454,6 +3470,10 @@ _("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; + int fd = -1; + struct fsuuid *fsuuid = NULL; + errcode_t ret = -1; if (ext2fs_has_feature_stable_inodes(fs->super)) { fputs(_("Cannot change the UUID of this filesystem " @@ -3507,25 +3527,62 @@ _("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)) { + if ((mount_flags & EXT2_MF_MOUNTED) && + !(mount_flags & EXT2_MF_READONLY) && mntpt) { + fd = open(mntpt, O_RDONLY); + if (fd >= 0) { + fsuuid = malloc(sizeof(*fsuuid) + UUID_SIZE); + if (!fsuuid) { + close(fd); + fd = -1; + } + } + } + + /* Get the filesystem uuid through the ioctl. + * If the filesystem is offline or the ioctl is unavailable or + * fails, fall back to directly modifiying the superblock. + */ + if (fd >= 0) { + fsuuid->fsu_len = UUID_SIZE; + fsuuid->fsu_flags = 0; + ret = ioctl(fd, EXT4_IOC_GETFSUUID, fsuuid); + } + if (ret) + 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; + + /* Set the filesystem uuid through the ioctl or fallback to + * directly modifying superblock. + */ + if (fd >= 0) { + fsuuid->fsu_len - UUID_SIZE; + fsuuid->fsu_flags = 0; + memcpy(&fsuuid->fsu_uuid, new_uuid, UUID_SIZE); + ret = ioctl(fd, EXT4_IOC_SETFSUUID, fsuuid); + } + if (ret) { + 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 */ @@ -3550,7 +3607,10 @@ _("Warning: The journal is dirty. You may wish to replay the journal like:\n\n" goto closefs; } - ext2fs_mark_super_dirty(fs); + if (fd >= 0) + close(fd); + if (fsuuid) + free(fsuuid); } if (I_flag) { -- 2.37.1.595.g718a3a8f04-goog