[Qemu-devel] [PATCH v5 3/4] crypto.c: cleanup created file when block_crypto_co_create_opts_luks fails

[Daniel Henrique Barboza <danielhb413@gmail.com>]

When using a non-UTF8 secret to create a volume using qemu-img, the
following error happens:

$ qemu-img create -f luks --object secret,id=vol_1_encrypt0,file=vol_resize_pool.vol_1.secret.qzVQrI -o key-secret=vol_1_encrypt0 /var/tmp/pool_target/vol_1 10240K

Formatting '/var/tmp/pool_target/vol_1', fmt=luks size=10485760 key-secret=vol_1_encrypt0
qemu-img: /var/tmp/pool_target/vol_1: Data from secret vol_1_encrypt0 is not valid UTF-8

However, the created file '/var/tmp/pool_target/vol_1' is left behind in the
file system after the failure. This behavior can be observed when creating
the volume using Libvirt, via 'virsh vol-create', and then getting "volume
target path already exist" errors when trying to re-create the volume.

The volume file is created inside block_crypto_co_create_opts_luks(), in
block/crypto.c. If the bdrv_create_file() call is successful but any
succeeding step fails*, the existing 'fail' label does not take into
account the created file, leaving it behind.

This patch changes block_crypto_co_create_opts_luks() to delete
'filename' in case of failure. A failure in this point means that
the volume is now truncated/corrupted, so even if 'filename' was an
existing volume before calling qemu-img, it is now unusable. Deleting
the file it is not much worse than leaving it in the filesystem in
this scenario, and we don't have to deal with checking the file
pre-existence in the code.

* in our case, block_crypto_co_create_generic calls qcrypto_block_create,
which calls qcrypto_block_luks_create, and this function fails when
calling qcrypto_secret_lookup_as_utf8.

Reported-by: Srikanth Aithal <bssrikanth@in.ibm.com>
Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
---
 block/crypto.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/block/crypto.c b/block/crypto.c
index 8237424ae6..8ffca81df6 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -30,6 +30,7 @@
 #include "qapi/error.h"
 #include "qemu/module.h"
 #include "qemu/option.h"
+#include "qemu/cutils.h"
 #include "crypto.h"
 
 typedef struct BlockCrypto BlockCrypto;
@@ -575,6 +576,25 @@ fail:
     bdrv_unref(bs);
     qapi_free_QCryptoBlockCreateOptions(create_opts);
     qobject_unref(cryptoopts);
+
+    /*
+     * If an error occurred, delete the file. Even if the file existed
+     * beforehand, it has been truncated and corrupted in the process.
+     */
+    if (ret) {
+        Error *local_err;
+        int r_del = bdrv_delete_file(filename, &local_err);
+        /*
+         * ENOTSUP will happen if the block driver doesn't support
+         * 'bdrv_co_delete_file'. ENOENT will happen if the file
+         * doesn't exist. Both are predictable and shouldn't be
+         * reported back to the user.
+         */
+        if ((r_del < 0) && (r_del != -ENOTSUP) && (r_del != -ENOENT)) {
+            error_reportf_err(local_err, "%s: ", bs->filename);
+        }
+    }
+
     return ret;
 }
 
-- 
2.21.0