code: plan9front

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disk/qcow2: fix crash with misaligned sectors

When looping over the pages in a misaligned sector,
we would null out the disk, rather than simply checking
whether the translation was done correctly.

diff: cannot open b/sys/src/cmd/disk/test//null: file does not exist: 'b/sys/src/cmd/disk/test//null'

--- a/sys/src/cmd/disk/qcowfs.c

+++ b/sys/src/cmd/disk/qcowfs.c

@@ -463,14 +463,15 @@

 	rem = len;

 	while(rem != 0){

 		phys_off = xlate(d, off, nil);

-		if(phys_off <= 0)

-			d = nil;

+		if(phys_off == -1){

+			responderror(r);

+			return;

+		}

 		cluster_off = off % disk->clustersz;

 		sz = disk->clustersz - cluster_off;

 		if(sz > rem)

 			sz = rem;

-

-		if(!d)

+		if(phys_off == 0)

 			memset(buf, 0, sz);

 		else

 			sz = pread(d->fd, buf, sz, phys_off);

--- /dev/null

+++ b/sys/src/cmd/disk/test/basic.rc

@@ -1,0 +1,28 @@

+#!/bin/rc

+

+# read fresh disk

+../$O.qcowfs -n 4294967296 /tmp/qcow

+dd -ibs 389120 -skip 1 -obs 8192 -count 1 < /mnt/qcow/data >/dev/null

+../$O.qcowfs -n 4294967296 /tmp/qcow

+dd -ibs 389120 -skip 1 -obs 15473 -count 1 < /mnt/qcow/data >/dev/null

+

+# write

+../$O.qcowfs -n 4294967296 /tmp/qcow

+dd -ibs 389120 -skip 1 -obs 8192 -count 1 -if /dev/random -of /mnt/qcow/data # start, power of two

+dd -ibs 389120 -skip 1 -obs 15473 -count 1 -if /dev/random -of /mnt/qcow/data # random prime

+dd -ibs 389120 -skip 1 -obs 8192 -seek 524287 -count 1 -if /dev/random -of /mnt/qcow/data  # end

+

+# read written disk

+dd -ibs 389120 -skip 1 -obs 8192 -count 1 < /mnt/qcow/data >/dev/null

+dd -ibs 389120 -skip 1 -obs 15473 -count 1 < /mnt/qcow/data >/dev/null

+

+# read and write some data

+cat /bin/cat > /mnt/qcow/data

+sz = `{walk -es /bin/cat}

+xhash=`{cat /bin/cat | sha1sum}

+rhash=`{read -c $sz /mnt/qcow/data | sha1sum}

+if(! ~ $xhash $rhash){

+	>[1=2] echo mismatched data

+	exit mishash

+}

+exit ''

--- /dev/null

+++ b/sys/src/cmd/disk/test/mkfile

@@ -1,0 +1,6 @@

+</$objtype/mkfile

+

+TEST=\

+	basic

+

+</sys/src/cmd/mktest