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libblkid/src/superblocks/ext.c
425 строк
12 KB
胡玮文
libblkid: (ext) reduce false positive
28 июл 2025, 09:57
28 июл 2025, 09:57
0c5d55e
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/* * Copyright (C) 1999, 2001 by Andries Brouwer * Copyright (C) 1999, 2000, 2003 by Theodore Ts'o * Copyright (C) 2008 Karel Zak <kzak@redhat.com> * * This file may be redistributed under the terms of the * GNU Lesser General Public License. */ #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #include <errno.h> #include <ctype.h> #include <stdint.h> #ifdef __linux__ #include <sys/utsname.h> #endif #include <time.h> #include "superblocks.h" #include "crc32c.h" struct ext2_super_block { uint32_t s_inodes_count; uint32_t s_blocks_count; uint32_t s_r_blocks_count; uint32_t s_free_blocks_count; uint32_t s_free_inodes_count; uint32_t s_first_data_block; uint32_t s_log_block_size; uint32_t s_dummy3[7]; unsigned char s_magic[2]; uint16_t s_state; uint16_t s_errors; uint16_t s_minor_rev_level; uint32_t s_lastcheck; uint32_t s_checkinterval; uint32_t s_creator_os; uint32_t s_rev_level; uint16_t s_def_resuid; uint16_t s_def_resgid; uint32_t s_first_ino; uint16_t s_inode_size; uint16_t s_block_group_nr; uint32_t s_feature_compat; uint32_t s_feature_incompat; uint32_t s_feature_ro_compat; unsigned char s_uuid[16]; char s_volume_name[16]; char s_last_mounted[64]; uint32_t s_algorithm_usage_bitmap; uint8_t s_prealloc_blocks; uint8_t s_prealloc_dir_blocks; uint16_t s_reserved_gdt_blocks; uint8_t s_journal_uuid[16]; uint32_t s_journal_inum; uint32_t s_journal_dev; uint32_t s_last_orphan; uint32_t s_hash_seed[4]; uint8_t s_def_hash_version; uint8_t s_jnl_backup_type; uint16_t s_reserved_word_pad; uint32_t s_default_mount_opts; uint32_t s_first_meta_bg; uint32_t s_mkfs_time; uint32_t s_jnl_blocks[17]; uint32_t s_blocks_count_hi; uint32_t s_r_blocks_count_hi; uint32_t s_free_blocks_hi; uint16_t s_min_extra_isize; uint16_t s_want_extra_isize; uint32_t s_flags; uint16_t s_raid_stride; uint16_t s_mmp_interval; uint64_t s_mmp_block; uint32_t s_raid_stripe_width; uint32_t s_reserved[162]; uint32_t s_checksum; } __attribute__((packed)); /* magic string */ #define EXT_SB_MAGIC "\123\357" /* supper block offset */ #define EXT_SB_OFF 0x400 /* supper block offset in kB */ #define EXT_SB_KBOFF (EXT_SB_OFF >> 10) /* magic string offset within super block */ #define EXT_MAG_OFF 0x38 /* for s_flags */ #define EXT2_FLAGS_TEST_FILESYS 0x0004 /* for s_feature_compat */ #define EXT3_FEATURE_COMPAT_HAS_JOURNAL 0x0004 /* for s_feature_ro_compat */ #define EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER 0x0001 #define EXT2_FEATURE_RO_COMPAT_LARGE_FILE 0x0002 #define EXT2_FEATURE_RO_COMPAT_BTREE_DIR 0x0004 #define EXT4_FEATURE_RO_COMPAT_HUGE_FILE 0x0008 #define EXT4_FEATURE_RO_COMPAT_GDT_CSUM 0x0010 #define EXT4_FEATURE_RO_COMPAT_DIR_NLINK 0x0020 #define EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE 0x0040 #define EXT4_FEATURE_RO_COMPAT_METADATA_CSUM 0x0400 /* for s_feature_incompat */ #define EXT2_FEATURE_INCOMPAT_FILETYPE 0x0002 #define EXT3_FEATURE_INCOMPAT_RECOVER 0x0004 #define EXT3_FEATURE_INCOMPAT_JOURNAL_DEV 0x0008 #define EXT2_FEATURE_INCOMPAT_META_BG 0x0010 #define EXT4_FEATURE_INCOMPAT_EXTENTS 0x0040 /* extents support */ #define EXT4_FEATURE_INCOMPAT_64BIT 0x0080 #define EXT4_FEATURE_INCOMPAT_MMP 0x0100 #define EXT4_FEATURE_INCOMPAT_FLEX_BG 0x0200 #define EXT2_FEATURE_RO_COMPAT_SUPP (EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER| \ EXT2_FEATURE_RO_COMPAT_LARGE_FILE| \ EXT2_FEATURE_RO_COMPAT_BTREE_DIR) #define EXT2_FEATURE_INCOMPAT_SUPP (EXT2_FEATURE_INCOMPAT_FILETYPE| \ EXT2_FEATURE_INCOMPAT_META_BG) #define EXT2_FEATURE_INCOMPAT_UNSUPPORTED ~EXT2_FEATURE_INCOMPAT_SUPP #define EXT2_FEATURE_RO_COMPAT_UNSUPPORTED ~EXT2_FEATURE_RO_COMPAT_SUPP #define EXT3_FEATURE_RO_COMPAT_SUPP (EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER| \ EXT2_FEATURE_RO_COMPAT_LARGE_FILE| \ EXT2_FEATURE_RO_COMPAT_BTREE_DIR) #define EXT3_FEATURE_INCOMPAT_SUPP (EXT2_FEATURE_INCOMPAT_FILETYPE| \ EXT3_FEATURE_INCOMPAT_RECOVER| \ EXT2_FEATURE_INCOMPAT_META_BG) #define EXT3_FEATURE_INCOMPAT_UNSUPPORTED ~EXT3_FEATURE_INCOMPAT_SUPP #define EXT3_FEATURE_RO_COMPAT_UNSUPPORTED ~EXT3_FEATURE_RO_COMPAT_SUPP /* * Starting in 2.6.29, ext4 can be used to support filesystems * without a journal. */ #define EXT4_SUPPORTS_EXT2 KERNEL_VERSION(2, 6, 29) /* * reads superblock and returns: * fc = feature_compat * fi = feature_incompat * frc = feature_ro_compat */ static struct ext2_super_block *ext_get_super( blkid_probe pr, uint32_t *fc, uint32_t *fi, uint32_t *frc) { struct ext2_super_block *es; es = (struct ext2_super_block *) blkid_probe_get_buffer(pr, EXT_SB_OFF, sizeof(struct ext2_super_block)); if (!es) return NULL; if (le32_to_cpu(es->s_feature_ro_compat) & EXT4_FEATURE_RO_COMPAT_METADATA_CSUM) { uint32_t csum = crc32c(~0, es, offsetof(struct ext2_super_block, s_checksum)); /* * A read of the superblock can race with other updates to the * same superblock. In the unlikely event that this occurs and * we see a checksum failure, re-read the superblock with * O_DIRECT to ensure that it's consistent. If it _still_ fails * then declare a checksum mismatch. */ if (!blkid_probe_verify_csum(pr, csum, le32_to_cpu(es->s_checksum))) { #ifdef O_DIRECT if (blkid_probe_reset_buffers(pr)) return NULL; es = (struct ext2_super_block *) blkid_probe_get_buffer_direct(pr, EXT_SB_OFF, sizeof(struct ext2_super_block)); if (!es) return NULL; csum = crc32c(~0, es, offsetof(struct ext2_super_block, s_checksum)); if (!blkid_probe_verify_csum(pr, csum, le32_to_cpu(es->s_checksum))) return NULL; #else return NULL; #endif } } else { /* * For legacy fs without checksum, additionally verify the * block size to reduce false positive. Currently max allowed * block size is 64KiB (s_log_block_size <= 6), check for 256 * to be more future proof. */ if (le32_to_cpu(es->s_log_block_size) >= 256) return NULL; } if (fc) *fc = le32_to_cpu(es->s_feature_compat); if (fi) *fi = le32_to_cpu(es->s_feature_incompat); if (frc) *frc = le32_to_cpu(es->s_feature_ro_compat); return es; } static void ext_get_info(blkid_probe pr, int ver, struct ext2_super_block *es) { struct blkid_chain *chn = blkid_probe_get_chain(pr); uint32_t s_feature_incompat = le32_to_cpu(es->s_feature_incompat); DBG(PROBE, ul_debug("ext2_sb.compat = %08X:%08X:%08X", le32_to_cpu(es->s_feature_compat), s_feature_incompat, le32_to_cpu(es->s_feature_ro_compat))); if (*es->s_volume_name != '\0') blkid_probe_set_label(pr, (unsigned char *) es->s_volume_name, sizeof(es->s_volume_name)); blkid_probe_set_uuid(pr, es->s_uuid); if (le32_to_cpu(es->s_feature_compat) & EXT3_FEATURE_COMPAT_HAS_JOURNAL) blkid_probe_set_uuid_as(pr, es->s_journal_uuid, "EXT_JOURNAL"); if (ver != 2 && (chn->flags & BLKID_SUBLKS_SECTYPE) && ((s_feature_incompat & EXT2_FEATURE_INCOMPAT_UNSUPPORTED) == 0)) blkid_probe_set_value(pr, "SEC_TYPE", (unsigned char *) "ext2", sizeof("ext2")); blkid_probe_sprintf_version(pr, "%u.%u", le32_to_cpu(es->s_rev_level), le16_to_cpu(es->s_minor_rev_level)); uint32_t block_size = 0; if (le32_to_cpu(es->s_log_block_size) < 32){ block_size = 1024U << le32_to_cpu(es->s_log_block_size); blkid_probe_set_fsblocksize(pr, block_size); blkid_probe_set_block_size(pr, block_size); } uint64_t fslastblock = le32_to_cpu(es->s_blocks_count) | ((s_feature_incompat & EXT4_FEATURE_INCOMPAT_64BIT) ? (uint64_t) le32_to_cpu(es->s_blocks_count_hi) << 32 : 0); blkid_probe_set_fslastblock(pr, fslastblock); /* The total number of blocks is taken without subtraction of overhead * (journal, metadata). The ext4 has non-trivial overhead calculation * viz. ext4_calculate_overhead(). Therefore, the FSSIZE would show number * slightly higher than the real value (for example, calculated via * statfs()). */ uint64_t fssize = (uint64_t) block_size * le32_to_cpu(es->s_blocks_count); blkid_probe_set_fssize(pr, fssize); } static int probe_jbd(blkid_probe pr, const struct blkid_idmag *mag __attribute__((__unused__))) { struct ext2_super_block *es; uint32_t fi; es = ext_get_super(pr, NULL, &fi, NULL); if (!es) return errno ? -errno : 1; if (!(fi & EXT3_FEATURE_INCOMPAT_JOURNAL_DEV)) return 1; ext_get_info(pr, 2, es); blkid_probe_set_uuid_as(pr, es->s_uuid, "LOGUUID"); return 0; } static int probe_ext2(blkid_probe pr, const struct blkid_idmag *mag __attribute__((__unused__))) { struct ext2_super_block *es; uint32_t fc, frc, fi; es = ext_get_super(pr, &fc, &fi, &frc); if (!es) return errno ? -errno : 1; /* Distinguish between ext3 and ext2 */ if (fc & EXT3_FEATURE_COMPAT_HAS_JOURNAL) return 1; /* Any features which ext2 doesn't understand */ if ((frc & EXT2_FEATURE_RO_COMPAT_UNSUPPORTED) || (fi & EXT2_FEATURE_INCOMPAT_UNSUPPORTED)) return 1; ext_get_info(pr, 2, es); return 0; } static int probe_ext3(blkid_probe pr, const struct blkid_idmag *mag __attribute__((__unused__))) { struct ext2_super_block *es; uint32_t fc, frc, fi; es = ext_get_super(pr, &fc, &fi, &frc); if (!es) return errno ? -errno : 1; /* ext3 requires journal */ if (!(fc & EXT3_FEATURE_COMPAT_HAS_JOURNAL)) return 1; /* Any features which ext3 doesn't understand */ if ((frc & EXT3_FEATURE_RO_COMPAT_UNSUPPORTED) || (fi & EXT3_FEATURE_INCOMPAT_UNSUPPORTED)) return 1; ext_get_info(pr, 3, es); return 0; } static int probe_ext4dev(blkid_probe pr, const struct blkid_idmag *mag __attribute__((__unused__))) { struct ext2_super_block *es; uint32_t fc, frc, fi; es = ext_get_super(pr, &fc, &fi, &frc); if (!es) return errno ? -errno : 1; /* Distinguish from jbd */ if (fi & EXT3_FEATURE_INCOMPAT_JOURNAL_DEV) return 1; if (!(le32_to_cpu(es->s_flags) & EXT2_FLAGS_TEST_FILESYS)) return 1; ext_get_info(pr, 4, es); return 0; } static int probe_ext4(blkid_probe pr, const struct blkid_idmag *mag __attribute__((__unused__))) { struct ext2_super_block *es; uint32_t fc, frc, fi; es = ext_get_super(pr, &fc, &fi, &frc); if (!es) return errno ? -errno : 1; /* Distinguish from jbd */ if (fi & EXT3_FEATURE_INCOMPAT_JOURNAL_DEV) return 1; /* Ext4 has at least one feature which ext3 doesn't understand */ if (!(frc & EXT3_FEATURE_RO_COMPAT_UNSUPPORTED) && !(fi & EXT3_FEATURE_INCOMPAT_UNSUPPORTED)) return 1; /* * If the filesystem is a OK for use by in-development * filesystem code, and ext4dev is supported or ext4 is not * supported, then don't call ourselves ext4, so we can redo * the detection and mark the filesystem as ext4dev. * * If the filesystem is marked as in use by production * filesystem, then it can only be used by ext4 and NOT by * ext4dev. */ if (le32_to_cpu(es->s_flags) & EXT2_FLAGS_TEST_FILESYS) return 1; ext_get_info(pr, 4, es); return 0; } #define BLKID_EXT_MAGICS \ { \ { \ .magic = EXT_SB_MAGIC, \ .len = sizeof(EXT_SB_MAGIC) - 1, \ .kboff = EXT_SB_KBOFF, \ .sboff = EXT_MAG_OFF \ }, \ { NULL } \ } const struct blkid_idinfo jbd_idinfo = { .name = "jbd", .usage = BLKID_USAGE_OTHER, .probefunc = probe_jbd, .magics = BLKID_EXT_MAGICS }; const struct blkid_idinfo ext2_idinfo = { .name = "ext2", .usage = BLKID_USAGE_FILESYSTEM, .probefunc = probe_ext2, .magics = BLKID_EXT_MAGICS }; const struct blkid_idinfo ext3_idinfo = { .name = "ext3", .usage = BLKID_USAGE_FILESYSTEM, .probefunc = probe_ext3, .magics = BLKID_EXT_MAGICS }; const struct blkid_idinfo ext4_idinfo = { .name = "ext4", .usage = BLKID_USAGE_FILESYSTEM, .probefunc = probe_ext4, .magics = BLKID_EXT_MAGICS }; const struct blkid_idinfo ext4dev_idinfo = { .name = "ext4dev", .usage = BLKID_USAGE_FILESYSTEM, .probefunc = probe_ext4dev, .magics = BLKID_EXT_MAGICS };