aab06b8a4d
Do some range checks on FSINFO values to make sure they are valid. Fixes issue reported by dos386 on the mailing list. git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@1631 6ac86273-5f31-0410-b378-82cca8765d1b
414 lines
13 KiB
C
414 lines
13 KiB
C
/****************************************************************/
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/* */
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/* fattab.c */
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/* */
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/* FAT File System Table Functions */
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/* */
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/* Copyright (c) 1995 */
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/* Pasquale J. Villani */
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/* All Rights Reserved */
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/* */
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/* This file is part of DOS-C. */
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/* */
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/* DOS-C is free software; you can redistribute it and/or */
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/* modify it under the terms of the GNU General Public License */
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/* as published by the Free Software Foundation; either version */
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/* 2, or (at your option) any later version. */
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/* */
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/* DOS-C is distributed in the hope that it will be useful, but */
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/* WITHOUT ANY WARRANTY; without even the implied warranty of */
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/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See */
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/* the GNU General Public License for more details. */
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/* */
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/* You should have received a copy of the GNU General Public */
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/* License along with DOS-C; see the file COPYING. If not, */
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/* write to the Free Software Foundation, 675 Mass Ave, */
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/* Cambridge, MA 02139, USA. */
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/****************************************************************/
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#include "portab.h"
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#include "globals.h"
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#ifdef VERSION_STRINGS
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static BYTE *RcsId =
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"$Id$";
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#endif
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/************************************************************************/
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/* */
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/* cluster/sector routines */
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/* */
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/************************************************************************/
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/* special "impossible" "Cluster2" value of 1 denotes reading the
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cluster number rather than overwriting it */
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#define READ_CLUSTER 1
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#ifndef ISFAT32
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int ISFAT32(struct dpb FAR * dpbp)
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{
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return _ISFAT32(dpbp);
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}
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#endif
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void clusterMessage(const char * msg, CLUSTER clussec)
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{
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put_string("Run chkdsk: Bad FAT ");
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put_string(msg);
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#ifdef WITHFAT32
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put_unsigned((unsigned)(clussec >> 16), 16, 4);
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#endif
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put_unsigned((unsigned)(clussec & 0xffffu), 16, 4);
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put_console('\n');
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}
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struct buffer FAR *getFATblock(struct dpb FAR * dpbp, CLUSTER clussec)
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{
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/* *** why dpbp->dpb_unit? only useful to know in context of the dpbp...? *** */
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struct buffer FAR *bp = getblock(clussec, dpbp->dpb_unit);
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if (bp)
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{
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bp->b_flag &= ~(BFR_DATA | BFR_DIR);
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bp->b_flag |= BFR_FAT | BFR_VALID;
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bp->b_dpbp = dpbp;
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bp->b_copies = dpbp->dpb_fats;
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bp->b_offset = dpbp->dpb_fatsize; /* 0 for FAT32 but blockio.c knows that */
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#ifdef WITHFAT32
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if (ISFAT32(dpbp))
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{
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if (dpbp->dpb_xflags & FAT_NO_MIRRORING)
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bp->b_copies = 1;
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}
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#endif
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} else {
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clusterMessage("I/O: 0x",clussec);
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}
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return bp;
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}
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#ifdef WITHFAT32
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void read_fsinfo(struct dpb FAR * dpbp)
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{
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struct buffer FAR *bp;
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struct fsinfo FAR *fip;
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CLUSTER cluster;
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if (dpbp->dpb_xfsinfosec == 0xffff)
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return;
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bp = getblock(dpbp->dpb_xfsinfosec, dpbp->dpb_unit);
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bp->b_flag &= ~(BFR_DATA | BFR_DIR | BFR_FAT | BFR_DIRTY);
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bp->b_flag |= BFR_VALID;
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fip = (struct fsinfo FAR *)&bp->b_buffer[0x1e4];
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/* need to range check values because they may not be correct */
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cluster = fip->fi_nfreeclst;
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if (cluster >= dpbp->dpb_xsize)
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cluster = XUNKNCLSTFREE;
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dpbp->dpb_xnfreeclst = cluster;
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cluster = fip->fi_cluster;
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if (cluster < 2 || cluster > dpbp->dpb_xsize)
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cluster = UNKNCLUSTER;
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dpbp->dpb_xcluster = cluster;
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}
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void write_fsinfo(struct dpb FAR * dpbp)
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{
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struct buffer FAR *bp;
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struct fsinfo FAR *fip;
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if (dpbp->dpb_xfsinfosec == 0xffff)
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return;
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bp = getblock(dpbp->dpb_xfsinfosec, dpbp->dpb_unit);
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bp->b_flag &= ~(BFR_DATA | BFR_DIR | BFR_FAT);
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bp->b_flag |= BFR_VALID;
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fip = (struct fsinfo FAR *)&bp->b_buffer[0x1e4];
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if (fip->fi_nfreeclst != dpbp->dpb_xnfreeclst ||
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fip->fi_cluster != dpbp->dpb_xcluster)
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bp->b_flag |= BFR_DIRTY; /* only flag for update if we had real news */
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fip->fi_nfreeclst = dpbp->dpb_xnfreeclst;
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fip->fi_cluster = dpbp->dpb_xcluster;
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}
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#endif
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/* */
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/* The FAT file system is difficult to trace through FAT table. */
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/* There are two kinds of FATs, 12 bit and 16 bit. The 16 bit */
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/* FAT is the easiest, since it is nothing more than a series */
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/* of UWORDs. The 12 bit FAT is difficult, because it packs 3 */
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/* FAT entries into two BYTEs. These are packed as follows: */
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/* */
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/* 0x0003 0x0004 0x0005 0x0006 0x0007 0x0008 0x0009 ... */
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/* */
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/* are packed as */
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/* */
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/* 0x03 0x40 0x00 0x05 0x60 0x00 0x07 0x80 0x00 0x09 ... */
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/* */
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/* 12 bytes are compressed to 9 bytes */
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/* */
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/* either read the value at Cluster1 (if Cluster2 is READ_CLUSTER) */
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/* or write the Cluster2 value to the FAT entry at Cluster1 */
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/* Read is always via next_cluster wrapper which has extra checks */
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/* It might make sense to manually check old values before a write */
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/* returns: the cluster number (or 1 on error) for read mode */
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/* returns: SUCCESS (or 1 on error) for write mode */
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CLUSTER link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
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REG CLUSTER Cluster2)
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{
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struct buffer FAR *bp;
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unsigned idx;
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unsigned secdiv; /* FAT entries per sector; nibbles for FAT12! */
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unsigned char wasfree;
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CLUSTER clussec = Cluster1;
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CLUSTER max_cluster = dpbp->dpb_size;
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#ifdef WITHFAT32
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if (ISFAT32(dpbp))
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max_cluster = dpbp->dpb_xsize;
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#endif
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if (clussec <= 1 || clussec > max_cluster) /* try to read out of range? */
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{
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clusterMessage("index: 0x",clussec); /* bad array offset */
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return 1;
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}
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/* Cluster2 can 0 (FREE) or 1 (READ_CLUSTER), a cluster nr. >= 2, */
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/* (range check this case!) LONG_LAST_CLUSTER or LONG_BAD here... */
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if (Cluster2 < LONG_BAD && Cluster2 > max_cluster) /* writing bad value? */
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{
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clusterMessage("write: 0x",Cluster2); /* refuse to write bad value */
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return 1;
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}
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secdiv = dpbp->dpb_secsize;
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if (ISFAT12(dpbp))
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{
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clussec = (unsigned)clussec * 3;
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secdiv *= 2;
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}
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else /* FAT16 or FAT32 */
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{
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secdiv /= 2;
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#ifdef WITHFAT32
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if (ISFAT32(dpbp))
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secdiv /= 2;
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#endif
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}
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/* idx is a pointer to an index which is the nibble offset of the FAT
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entry within the sector for FAT12, or word offset for FAT16, or
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dword offset for FAT32 */
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idx = (unsigned)(clussec % secdiv);
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clussec /= secdiv;
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clussec += dpbp->dpb_fatstrt;
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#ifdef WITHFAT32
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if (ISFAT32(dpbp) && (dpbp->dpb_xflags & FAT_NO_MIRRORING))
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{
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/* we must modify the active fat,
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it's number is in the 0-3 bits of dpb_xflags */
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clussec += (dpbp->dpb_xflags & 0xf) * dpbp->dpb_xfatsize;
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}
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#endif
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/* Get the block that this cluster is in */
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bp = getFATblock(dpbp, clussec);
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if (bp == NULL) {
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return 1; /* the only error code possible here */
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}
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if (ISFAT12(dpbp))
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{
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REG UBYTE FAR *fbp0, FAR * fbp1;
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struct buffer FAR * bp1;
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unsigned cluster, cluster2;
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/* form an index so that we can read the block as a */
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/* byte array */
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idx /= 2;
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/* Test to see if the cluster straddles the block. If */
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/* it does, get the next block and use both to form the */
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/* the FAT word. Otherwise, just point to the next */
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/* block. */
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fbp0 = &bp->b_buffer[idx];
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/* pointer to next byte, will be overwritten, if not valid */
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fbp1 = fbp0 + 1;
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if (idx >= (unsigned)dpbp->dpb_secsize - 1)
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{
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/* blockio.c LRU logic ensures that bp != bp1 */
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bp1 = getFATblock(dpbp, (unsigned)clussec + 1);
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if (bp1 == 0)
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return 1; /* the only error code possible here */
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if (Cluster2 != READ_CLUSTER)
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bp1->b_flag |= BFR_DIRTY | BFR_VALID;
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fbp1 = &bp1->b_buffer[0];
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}
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cluster = *fbp0 | (*fbp1 << 8);
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{
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unsigned res = cluster;
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/* Now to unpack the contents of the FAT entry. Odd and */
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/* even bytes are packed differently. */
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if (Cluster1 & 0x01)
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cluster >>= 4;
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cluster &= 0x0fff;
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if ((unsigned)Cluster2 == READ_CLUSTER)
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{
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if (cluster >= MASK12)
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return LONG_LAST_CLUSTER;
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if (cluster == BAD12)
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return LONG_BAD;
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return cluster;
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}
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wasfree = 0;
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if (cluster == FREE)
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wasfree = 1;
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cluster = res;
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}
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/* Cluster2 may be set to LONG_LAST_CLUSTER == 0x0FFFFFFFUL or 0xFFFF */
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/* -- please don't remove this mask! */
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cluster2 = (unsigned)Cluster2 & 0x0fff;
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/* Now pack the value in */
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if ((unsigned)Cluster1 & 0x01)
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{
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cluster &= 0x000f;
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cluster2 <<= 4;
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}
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else
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{
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cluster &= 0xf000;
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}
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cluster |= cluster2;
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*fbp0 = (UBYTE)cluster;
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*fbp1 = (UBYTE)(cluster >> 8);
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}
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else if (ISFAT16(dpbp))
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{
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/* form an index so that we can read the block as a */
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/* byte array */
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/* and get the cluster number */
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UWORD res = fgetword(&bp->b_buffer[idx * 2]);
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if ((unsigned)Cluster2 == READ_CLUSTER)
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{
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if (res >= MASK16)
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return LONG_LAST_CLUSTER;
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if (res == BAD16)
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return LONG_BAD;
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return res;
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}
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/* Finally, put the word into the buffer and mark the */
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/* buffer as dirty. */
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fputword(&bp->b_buffer[idx * 2], (UWORD)Cluster2);
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wasfree = 0;
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if (res == FREE)
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wasfree = 1;
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}
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#ifdef WITHFAT32
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else if (ISFAT32(dpbp))
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{
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/* form an index so that we can read the block as a */
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/* byte array */
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UDWORD res = fgetlong(&bp->b_buffer[idx * 4]) & LONG_LAST_CLUSTER;
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if (Cluster2 == READ_CLUSTER)
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{
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if (res > LONG_BAD)
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return LONG_LAST_CLUSTER;
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return res;
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}
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/* Finally, put the word into the buffer and mark the */
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/* buffer as dirty. */
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fputlong(&bp->b_buffer[idx * 4], Cluster2 & LONG_LAST_CLUSTER);
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wasfree = 0;
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if (res == FREE)
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wasfree = 1;
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}
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#endif
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else {
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put_string("Bad DPB!\n"); /* FAT1x size field > 65525U (see fat.h) */
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return 1;
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}
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/* update the free space count */
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bp->b_flag |= BFR_DIRTY | BFR_VALID;
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if (Cluster2 == FREE || wasfree)
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{
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int adjust = 0;
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if (!wasfree)
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adjust = 1;
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else if (Cluster2 != FREE)
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adjust = -1;
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#ifdef WITHFAT32
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if (ISFAT32(dpbp) && dpbp->dpb_xnfreeclst != XUNKNCLSTFREE)
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{
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/* update the free space count for returned */
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/* cluster */
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dpbp->dpb_xnfreeclst += adjust;
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write_fsinfo(dpbp);
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}
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else
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#endif
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if (dpbp->dpb_nfreeclst != UNKNCLSTFREE)
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dpbp->dpb_nfreeclst += adjust;
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}
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return SUCCESS;
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}
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/* Given the disk parameters, and a cluster number, this function */
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/* looks at the FAT, and returns the next cluster in the clain or */
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/* 0 if there is no chain, 1 on error, LONG_LAST_CLUSTER at end. */
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CLUSTER next_cluster(struct dpb FAR * dpbp, CLUSTER ClusterNum)
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{
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CLUSTER candidate, following, max_cluster;
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candidate = link_fat(dpbp, ClusterNum, READ_CLUSTER);
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/* empty (0) error (1) bad (LONG_BAD) last (>LONG_BAD) need no checks */
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#if 0
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if (candidate == ClusterNum)
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return 1; /* chain has a tiny loop - easy but boring error check */
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#endif
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if (candidate < 2 || candidate >= LONG_BAD)
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return candidate;
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max_cluster = dpbp->dpb_size;
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#ifdef WITHFAT32
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if (ISFAT32(dpbp))
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max_cluster = dpbp->dpb_xsize;
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#endif
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/* FAT entry points to a possibly invalid next cluster */
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following = link_fat(dpbp, candidate, READ_CLUSTER);
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if (following<2 || (following < LONG_BAD && following > max_cluster))
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{
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/* chain must not contain free or out of range clusters */
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clusterMessage("value: 0x",following); /* read returned bad value */
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return 1; /* only possible error code here */
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}
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/* without checking "following", a chain can dangle to a free cluster: */
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/* if that cluster is later used by another chain, you get cross links */
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return candidate;
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}
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/* check if the selected cluster is free (faster than next_cluster) */
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BOOL is_free_cluster(struct dpb FAR * dpbp, CLUSTER ClusterNum)
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{
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return (link_fat(dpbp, ClusterNum, READ_CLUSTER) == FREE);
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}
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