commit 9b2063dbcfc4cae161564754323bb8efe7cd0de5
author J. Richard Barnette <jrbarnette@chromium.org> Mon Jan 23 15:04:08 2012 -0800
committer Richard Barnette <jrbarnette@chromium.org> Tue Jan 24 16:05:34 2012 -0800
tree 2fdb2d09e6809be946e9a6dff3105e826cb2380b
parent 1853cc21b01eb2324442d275b3ec1ef965746681

Fix a race condition when mounting loopback devices.

The previous code selected and configured the loopback device in two
separate stages.  This allowed for the possiblity that some other
code could claim the same loopback claimed by patch_kernel, leading
to failures.

BUG=chromium-os:24975
TEST=cros_generate_update_payload --output=<outfile> --image=<infile> --patch_kernel
TEST=image_to_live.sh

Change-Id: Ic081189f9431cb037a8b0eb02f0f9a19ad39d6d2
Reviewed-on: https://gerrit.chromium.org/gerrit/14716
Reviewed-by: David James <davidjames@chromium.org>
Tested-by: Richard Barnette <jrbarnette@chromium.org>

host/cros_generate_update_payload

diff --git a/host/cros_generate_update_payload b/host/cros_generate_update_payload
index af1c4bc..edbf303 100755
--- a/host/cros_generate_update_payload
+++ b/host/cros_generate_update_payload
@@ -47,7 +47,6 @@
 DST_KERNEL=""
 DST_ROOT=""
 STATE_MNT=""
-STATE_LOOP_DEV=""
 
 # Pass an arg to not exit 1 at the end
 cleanup() {
@@ -63,14 +62,10 @@
     DST_MNT=""
   fi
   if [ -n "$STATE_MNT" ]; then
-    sudo umount "$STATE_MNT"
+    sudo umount -d "$STATE_MNT" || true
     [ -d "$STATE_MNT" ] && rmdir "$STATE_MNT"
     STATE_MNT=""
   fi
-  if [ -n "$STATE_LOOP_DEV" ]; then
-    sudo losetup -d "$STATE_LOOP_DEV"
-    STATE_LOOP_DEV=""
-  fi
   rm -f "$SRC_KERNEL"
   rm -f "$SRC_ROOT"
   rm -f "$DST_KERNEL"
@@ -109,18 +104,14 @@
 
   echo "Patching kernel" $KERN_FILE
   echo "   into" $IMAGE
-  STATE_LOOP_DEV=$(sudo losetup -f)
-  [ -n "$STATE_LOOP_DEV" ] || die "no free loop device"
   local offset=$(partoffset "${IMAGE}" 1)
   offset=$(($offset * 512))
-  sudo losetup -o "$offset" "$STATE_LOOP_DEV" "$IMAGE"
   STATE_MNT=$(mktemp -d /tmp/state.XXXXXX)
-  sudo mount --read-only "$STATE_LOOP_DEV" "$STATE_MNT"
+  sudo mount -o ro,loop,offset=$offset "$IMAGE" "$STATE_MNT"
   dd if="$STATE_MNT"/vmlinuz_hd.vblock of="$KERN_FILE" conv=notrunc 2>/dev/null
-  sudo umount "$STATE_MNT"
+  sudo umount -d "$STATE_MNT"
+  rmdir "$STATE_MNT"
   STATE_MNT=""
-  sudo losetup -d "$STATE_LOOP_DEV"
-  STATE_LOOP_DEV=""
 }
 
 extract_kern_root() {