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Do not use FSINFO structure if it is not present.

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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
This commit is contained in:
Bart Oldeman 2011-06-13 16:27:34 +00:00
parent aec735eecd
commit aab06b8a4d
1 changed files with 16 additions and 2 deletions
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18
kernel/fattab.c
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@ -92,14 +92,25 @@ void read_fsinfo(struct dpb FAR * dpbp)
{
struct buffer FAR *bp;
struct fsinfo FAR *fip;
CLUSTER cluster;
if (dpbp->dpb_xfsinfosec == 0xffff)
return;
bp = getblock(dpbp->dpb_xfsinfosec, dpbp->dpb_unit);
bp->b_flag &= ~(BFR_DATA | BFR_DIR | BFR_FAT | BFR_DIRTY);
bp->b_flag |= BFR_VALID;
fip = (struct fsinfo FAR *)&bp->b_buffer[0x1e4];
dpbp->dpb_xnfreeclst = fip->fi_nfreeclst;
dpbp->dpb_xcluster = fip->fi_cluster;
/* need to range check values because they may not be correct */
cluster = fip->fi_nfreeclst;
if (cluster >= dpbp->dpb_xsize)
cluster = XUNKNCLSTFREE;
dpbp->dpb_xnfreeclst = cluster;
cluster = fip->fi_cluster;
if (cluster < 2 || cluster > dpbp->dpb_xsize)
cluster = UNKNCLUSTER;
dpbp->dpb_xcluster = cluster;
}
void write_fsinfo(struct dpb FAR * dpbp)
@ -107,6 +118,9 @@ void write_fsinfo(struct dpb FAR * dpbp)
struct buffer FAR *bp;
struct fsinfo FAR *fip;
if (dpbp->dpb_xfsinfosec == 0xffff)
return;
bp = getblock(dpbp->dpb_xfsinfosec, dpbp->dpb_unit);
bp->b_flag &= ~(BFR_DATA | BFR_DIR | BFR_FAT);
bp->b_flag |= BFR_VALID;