code: plan9front

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dossrv: better error handling and sanity checking in dosfs()

check error for devread() and do some sanity checking
on the constants and dont leak the Dosbpb when error.

--- a/sys/src/cmd/dossrv/dosfs.c

+++ b/sys/src/cmd/dossrv/dosfs.c

@@ -45,9 +45,12 @@

 	root->xf = xf = getxfs(req->uname, req->aname);

 	if(!xf)

 		goto error;

-	if(xf->fmt == 0 && dosfs(xf) < 0){

-		errno = Eformat;

-		goto error;

+	if(xf->fmt == 0){

+		if(dosfs(xf) < 0){

+			errno = Eformat;

+			goto error;

+		}

+		xf->fmt = 1;

 	}

 	root->qid.type = QTDIR;

 	root->qid.path = 0;

--- a/sys/src/cmd/dossrv/dossubs.c

+++ b/sys/src/cmd/dossrv/dossubs.c

@@ -41,7 +41,7 @@

 {

 	Iosect *p1;

 	Fatinfo *fi;

-	uchar	buf[512];

+	uchar buf[512];

 	Dosboot *b;

 	Dosboot32 *b32;

 	Dosbpb *bp;

@@ -73,28 +73,31 @@

 		isdos['&'] = 1;

 	}

-	/* don't use getsect() before we we determinted real values */

-	xf->sectsize = 512;

-	xf->sect2trk = 9;

-	devread(xf, 0, buf, sizeof(buf));

+	/* don't use getsect() before determining sector size */

+	if(devread(xf, 0, buf, sizeof(buf)) < 0)

+		return -1;

 	if(!isdosfs(buf))

 		return -1;

-	b = (Dosboot*)buf;

-

-	xf->sectsize = GSHORT(b->sectsize);

-	if(xf->sectsize < 32)

+	bp = malloc(sizeof(Dosbpb));

+	if(bp == nil)

 		return -1;

+	memset(bp, 0, sizeof(Dosbpb));	/* clear lock */

+	b = (Dosboot*)buf;

+	xf->sectsize = GSHORT(b->sectsize);

+	if(xf->sectsize < 32){

+		if(chatty)

+			fprint(2, "sectsize %d\n", xf->sectsize);

+		goto badfmt;

+	}

 	xf->sect2trk = GSHORT(b->trksize);

-	if(xf->sect2trk < 1)

-		return -1;

-

-	bp = malloc(sizeof(Dosbpb));

-	memset(bp, 0, sizeof(Dosbpb));	/* clear lock */

-	xf->ptr = bp;

-	xf->fmt = 1;

+	if(xf->sect2trk == 0){

+		if(chatty)

+			fprint(2, "sect2trk %d\n", xf->sect2trk);

+		goto badfmt;

+	}

 	bp->clustsize = b->clustsize;

 	bp->nresrv = GSHORT(b->nresrv);

 	bp->nfats = b->nfats;

@@ -117,7 +120,7 @@

 		if(bp->fatsize == 0){

 			if(chatty)

 				fprint(2, "fatsize 0\n");

-			return -1;

+			goto badfmt;

 		}

 		bp->dataaddr = bp->fataddr + bp->nfats*bp->fatsize;

 		bp->rootaddr = 0;

@@ -164,6 +167,16 @@

 		bp->dataaddr = bp->rootaddr + (bp->rootsize*DOSDIRSIZE + xf->sectsize-1)/xf->sectsize;

 		bp->freeptr = FATRESRV;

 	}

+	if(bp->clustsize == 0){

+		if(chatty)

+			fprint(2, "clustsize 0\n");

+		goto badfmt;

+	}

+	if(bp->volsize < bp->dataaddr){

+		if(chatty)

+			fprint(2, "volsize < dataaddr\n");

+		goto badfmt;

+	}

 	bp->fatclusters = FATRESRV + (bp->volsize - bp->dataaddr)/bp->clustsize;

 	if(xf->isfat32)

@@ -178,7 +191,12 @@

 		chat("fat %d: %lld...", i, bp->fataddr+i*bp->fatsize);

 	chat("root: %lld...", bp->rootaddr);

 	chat("data: %lld...", bp->dataaddr);

+

+	xf->ptr = bp;

 	return 0;

+badfmt:

+	free(bp);

+	return -1;

 }

 /*

--- a/sys/src/cmd/dossrv/xfile.c

+++ b/sys/src/cmd/dossrv/xfile.c

@@ -109,6 +109,8 @@

 	fxf->qid = dqid;

 	fxf->dev = fd;

 	fxf->fmt = 0;

+	fxf->sectsize = 0;

+	fxf->sect2trk = 0;

 	fxf->offset = offset;

 	fxf->ptr = nil;

 	fxf->isfat32 = 0;