code: plan9front

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libdisk: error handling, sanity checks

- make sure disk file is an actual file and not a directory, log or empty file
- sanity check: file has to be at least one sector to be a disk
- simplify error handling using freedisk()

--- a/sys/src/libdisk/disk.c

+++ b/sys/src/libdisk/disk.c

@@ -209,14 +209,25 @@

 }

 static Disk*

+freedisk(Disk *d)

+{

+	if(d->fd >= 0)

+		close(d->fd);

+	if(d->wfd >= 0)

+		close(d->wfd);

+	if(d->ctlfd >= 0)

+		close(d->ctlfd);

+	free(d);

+	return nil;

+}

+

+static Disk*

 openfile(Disk *disk)

 {

 	Dir *d;

-	if((d = dirfstat(disk->fd)) == nil){

-		free(disk);

-		return nil;

-	}

+	if((d = dirfstat(disk->fd)) == nil)

+		return freedisk(disk);

 	disk->secsize = 512;

 	disk->size = d->length;

@@ -224,6 +235,11 @@

 	disk->offset = 0;

 	free(d);

+	if(disk->secs == 0){

+		werrstr("file too small to be a disk");

+		return freedisk(disk);

+	}

+

 	findgeometry(disk);

 	return mkwidth(disk);

 }

@@ -274,6 +290,7 @@

 {

 	char *p, *q;

 	Disk *d;

+	Dir *s;

 	d = mallocz(sizeof(*d), 1);

 	if(d == nil)

@@ -284,10 +301,17 @@

 	d->fd = open(disk, OREAD);

 	if(d->fd < 0) {

-		werrstr("cannot open disk file");

-		free(d);

-		return nil;

+		werrstr("cannot open disk file: %r");

+		return freedisk(d);

 	}

+	if((s = dirfstat(d->fd)) == nil)

+		return freedisk(d);

+	if((s->mode & (DMDIR|DMAPPEND)) != 0){

+		free(s);

+		werrstr("not a disk file: %s", disk);

+		return freedisk(d);

+	}

+	free(s);

 	if(rdonly == 0) {

 		d->wfd = open(disk, OWRITE);

@@ -299,12 +323,8 @@

 		return openfile(d);

 	p = malloc(strlen(disk) + 4);	/* 4: slop for "ctl\0" */

-	if(p == nil) {

-		close(d->wfd);

-		close(d->fd);

-		free(d);

-		return nil;

-	}

+	if(p == nil)

+		return freedisk(d);

 	strcpy(p, disk);

 	/* check for floppy(3) disk */

@@ -334,12 +354,8 @@

 		d->type = Tsd;

 		d->part = strdup(disk+(q-p));

 		if(d->part == nil){

-			close(d->ctlfd);

-			close(d->wfd);

-			close(d->fd);

 			free(p);

-			free(d);

-			return nil;

+			return freedisk(d);

 		}

 		return opensd(d);

 	}