Index: head/sbin/fsck_msdosfs/boot.c =================================================================== --- head/sbin/fsck_msdosfs/boot.c (revision 356635) +++ head/sbin/fsck_msdosfs/boot.c (revision 356636) @@ -1,364 +1,375 @@ /*- * SPDX-License-Identifier: BSD-2-Clause-FreeBSD * * Copyright (C) 1995, 1997 Wolfgang Solfrank * Copyright (c) 1995 Martin Husemann * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include #ifndef lint __RCSID("$NetBSD: boot.c,v 1.21 2018/02/08 09:05:17 dholland Exp $"); static const char rcsid[] = "$FreeBSD$"; #endif /* not lint */ #include #include #include #include #include #include #include "ext.h" #include "fsutil.h" int readboot(int dosfs, struct bootblock *boot) { u_char block[DOSBOOTBLOCKSIZE]; u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; int ret = FSOK; if ((size_t)read(dosfs, block, sizeof block) != sizeof block) { perr("could not read boot block"); return FSFATAL; } if (block[510] != 0x55 || block[511] != 0xaa) { pfatal("Invalid signature in boot block: %02x%02x", block[511], block[510]); return FSFATAL; } memset(boot, 0, sizeof *boot); boot->ValidFat = -1; /* Decode BIOS Parameter Block */ /* Bytes per sector: can only be 512, 1024, 2048 and 4096. */ boot->bpbBytesPerSec = block[11] + (block[12] << 8); if (boot->bpbBytesPerSec < DOSBOOTBLOCKSIZE_REAL || boot->bpbBytesPerSec > DOSBOOTBLOCKSIZE || !powerof2(boot->bpbBytesPerSec)) { pfatal("Invalid sector size: %u", boot->bpbBytesPerSec); return FSFATAL; } /* Sectors per cluster: can only be: 1, 2, 4, 8, 16, 32, 64, 128. */ boot->bpbSecPerClust = block[13]; if (boot->bpbSecPerClust == 0 || !powerof2(boot->bpbSecPerClust)) { pfatal("Invalid cluster size: %u", boot->bpbSecPerClust); return FSFATAL; } /* Reserved sectors: must be non-zero */ boot->bpbResSectors = block[14] + (block[15] << 8); if (boot->bpbResSectors < 1) { pfatal("Invalid reserved sectors: %u", boot->bpbResSectors); return FSFATAL; } /* Number of FATs */ boot->bpbFATs = block[16]; if (boot->bpbFATs == 0) { pfatal("Invalid number of FATs: %u", boot->bpbFATs); return FSFATAL; } /* Root directory entries for FAT12 and FAT16 */ boot->bpbRootDirEnts = block[17] + (block[18] << 8); if (!boot->bpbRootDirEnts) { /* bpbRootDirEnts = 0 suggests that we are FAT32 */ boot->flags |= FAT32; } /* Total sectors (16 bits) */ boot->bpbSectors = block[19] + (block[20] << 8); if (boot->bpbSectors != 0 && (boot->flags & FAT32)) { pfatal("Invalid 16-bit total sector count on FAT32: %u", boot->bpbSectors); return FSFATAL; } /* Media type: ignored */ boot->bpbMedia = block[21]; /* FAT12/FAT16: 16-bit count of sectors per FAT */ boot->bpbFATsmall = block[22] + (block[23] << 8); if (boot->bpbFATsmall != 0 && (boot->flags & FAT32)) { pfatal("Invalid 16-bit FAT sector count on FAT32: %u", boot->bpbFATsmall); return FSFATAL; } /* Legacy CHS geometry numbers: ignored */ boot->SecPerTrack = block[24] + (block[25] << 8); boot->bpbHeads = block[26] + (block[27] << 8); /* Hidden sectors: ignored */ boot->bpbHiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + (block[31] << 24); /* Total sectors (32 bits) */ boot->bpbHugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + (block[35] << 24); if (boot->bpbHugeSectors == 0) { if (boot->flags & FAT32) { pfatal("FAT32 with sector count of zero"); return FSFATAL; } else if (boot->bpbSectors == 0) { pfatal("FAT with sector count of zero"); return FSFATAL; } boot->NumSectors = boot->bpbSectors; } else { if (boot->bpbSectors != 0) { pfatal("Invalid FAT sector count"); return FSFATAL; } boot->NumSectors = boot->bpbHugeSectors; } if (boot->flags & FAT32) { /* If the OEM Name field is EXFAT, it's not FAT32, so bail */ if (!memcmp(&block[3], "EXFAT ", 8)) { pfatal("exFAT filesystem is not supported."); return FSFATAL; } /* 32-bit count of sectors per FAT */ boot->FATsecs = block[36] + (block[37] << 8) + (block[38] << 16) + (block[39] << 24); if (block[40] & 0x80) boot->ValidFat = block[40] & 0x0f; /* FAT32 version, bail out if not 0.0 */ if (block[42] || block[43]) { pfatal("Unknown file system version: %x.%x", block[43], block[42]); return FSFATAL; } /* * Cluster number of the first cluster of root directory. * * Should be 2 but do not require it. */ boot->bpbRootClust = block[44] + (block[45] << 8) + (block[46] << 16) + (block[47] << 24); /* Sector number of the FSInfo structure, usually 1 */ boot->bpbFSInfo = block[48] + (block[49] << 8); /* Sector number of the backup boot block, ignored */ boot->bpbBackup = block[50] + (block[51] << 8); /* Check basic parameters */ if (boot->bpbFSInfo == 0) { /* * Either the BIOS Parameter Block has been corrupted, * or this is not a FAT32 filesystem, most likely an * exFAT filesystem. */ pfatal("Invalid FAT32 Extended BIOS Parameter Block"); return FSFATAL; } /* Read in and verify the FSInfo block */ if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET) != boot->bpbFSInfo * boot->bpbBytesPerSec || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) { perr("could not read fsinfo block"); return FSFATAL; } if (memcmp(fsinfo, "RRaA", 4) || memcmp(fsinfo + 0x1e4, "rrAa", 4) || fsinfo[0x1fc] || fsinfo[0x1fd] || fsinfo[0x1fe] != 0x55 || fsinfo[0x1ff] != 0xaa || fsinfo[0x3fc] || fsinfo[0x3fd] || fsinfo[0x3fe] != 0x55 || fsinfo[0x3ff] != 0xaa) { pwarn("Invalid signature in fsinfo block\n"); if (ask(0, "Fix")) { memcpy(fsinfo, "RRaA", 4); memcpy(fsinfo + 0x1e4, "rrAa", 4); fsinfo[0x1fc] = fsinfo[0x1fd] = 0; fsinfo[0x1fe] = 0x55; fsinfo[0x1ff] = 0xaa; fsinfo[0x3fc] = fsinfo[0x3fd] = 0; fsinfo[0x3fe] = 0x55; fsinfo[0x3ff] = 0xaa; if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET) != boot->bpbFSInfo * boot->bpbBytesPerSec || write(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) { perr("Unable to write bpbFSInfo"); return FSFATAL; } ret = FSBOOTMOD; } else boot->bpbFSInfo = 0; } else { /* We appear to have a valid FSInfo block, decode */ boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8) + (fsinfo[0x1ea] << 16) + (fsinfo[0x1eb] << 24); boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8) + (fsinfo[0x1ee] << 16) + (fsinfo[0x1ef] << 24); } } else { /* !FAT32: FAT12/FAT16 */ boot->FATsecs = boot->bpbFATsmall; } if (boot->FATsecs < 1 || boot->FATsecs > UINT32_MAX / boot->bpbFATs) { pfatal("Invalid FATs(%u) with FATsecs(%zu)", boot->bpbFATs, (size_t)boot->FATsecs); return FSFATAL; } boot->FirstCluster = (boot->bpbRootDirEnts * 32 + boot->bpbBytesPerSec - 1) / boot->bpbBytesPerSec + boot->bpbResSectors + boot->bpbFATs * boot->FATsecs; if (boot->FirstCluster + boot->bpbSecPerClust > boot->NumSectors) { pfatal("Cluster offset too large (%u clusters)\n", boot->FirstCluster); return FSFATAL; } - boot->NumClusters = (boot->NumSectors - boot->FirstCluster) / boot->bpbSecPerClust + - CLUST_FIRST; + /* + * The number of clusters is derived from available data sectors, divided + * by sectors per cluster. + */ + boot->NumClusters = (boot->NumSectors - boot->FirstCluster) / boot->bpbSecPerClust; if (boot->flags & FAT32) { if (boot->NumClusters > (CLUST_RSRVD & CLUST32_MASK)) { pfatal("Filesystem too big (%u clusters) for FAT32 partition", boot->NumClusters); return FSFATAL; } if (boot->NumClusters < (CLUST_RSRVD & CLUST16_MASK)) { pfatal("Filesystem too small (%u clusters) for FAT32 partition", boot->NumClusters); return FSFATAL; } boot->ClustMask = CLUST32_MASK; if (boot->bpbRootClust < CLUST_FIRST || boot->bpbRootClust >= boot->NumClusters) { pfatal("Root directory starts with cluster out of range(%u)", boot->bpbRootClust); return FSFATAL; } } else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK)) { boot->ClustMask = CLUST12_MASK; } else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK)) { boot->ClustMask = CLUST16_MASK; } else { pfatal("Filesystem too big (%u clusters) for non-FAT32 partition", boot->NumClusters); return FSFATAL; } switch (boot->ClustMask) { case CLUST32_MASK: boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 4; break; case CLUST16_MASK: boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec) / 2; break; default: boot->NumFatEntries = (boot->FATsecs * boot->bpbBytesPerSec * 2) / 3; break; } - if (boot->NumFatEntries < boot->NumClusters - CLUST_FIRST) { + if (boot->NumFatEntries < boot->NumClusters) { pfatal("FAT size too small, %u entries won't fit into %u sectors\n", boot->NumClusters, boot->FATsecs); return FSFATAL; } + + /* + * There are two reserved clusters. To avoid adding CLUST_FIRST every time + * when we perform boundary checks, we increment the NumClusters by 2, + * which is CLUST_FIRST to denote the first out-of-range cluster number. + */ + boot->NumClusters += CLUST_FIRST; + boot->ClusterSize = boot->bpbBytesPerSec * boot->bpbSecPerClust; boot->NumFiles = 1; boot->NumFree = 0; return ret; } int writefsinfo(int dosfs, struct bootblock *boot) { u_char fsinfo[2 * DOSBOOTBLOCKSIZE]; if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET) != boot->bpbFSInfo * boot->bpbBytesPerSec || read(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) { perr("could not read fsinfo block"); return FSFATAL; } fsinfo[0x1e8] = (u_char)boot->FSFree; fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8); fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16); fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24); fsinfo[0x1ec] = (u_char)boot->FSNext; fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8); fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16); fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24); if (lseek(dosfs, boot->bpbFSInfo * boot->bpbBytesPerSec, SEEK_SET) != boot->bpbFSInfo * boot->bpbBytesPerSec || write(dosfs, fsinfo, sizeof fsinfo) != sizeof fsinfo) { perr("Unable to write bpbFSInfo"); return FSFATAL; } /* * Technically, we should return FSBOOTMOD here. * * However, since Win95 OSR2 (the first M$ OS that has * support for FAT32) doesn't maintain the FSINFO block * correctly, it has to be fixed pretty often. * * Therefore, we handle the FSINFO block only informally, * fixing it if necessary, but otherwise ignoring the * fact that it was incorrect. */ return 0; }