[Qemu-devel] [PATCH v4 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 check if @filename
is an existing file before bdrv_create_file is called. In case of failure,
if @filename didn't exist before, check again for its existence and,
if affirmative, erase it by calling bdrv_delete_file.

* 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 | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/block/crypto.c b/block/crypto.c
index 8237424ae6..146f3eb721 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;
@@ -535,6 +536,8 @@ static int coroutine_fn block_crypto_co_create_opts_luks(const char *filename,
     BlockDriverState *bs = NULL;
     QDict *cryptoopts;
     int64_t size;
+    const char *path;
+    bool file_already_existed = false;
     int ret;
 
     /* Parse options */
@@ -551,6 +554,15 @@ static int coroutine_fn block_crypto_co_create_opts_luks(const char *filename,
         goto fail;
     }
 
+    /*
+     * Check if 'filename' represents a local file that already
+     * exists in the file system prior to bdrv_create_file. Strip
+     * the leading 'file:' from the filename if it exists.
+     */
+    path = filename;
+    strstart(path, "file:", &path);
+    file_already_existed = bdrv_path_is_regular_file(path);
+
     /* Create protocol layer */
     ret = bdrv_create_file(filename, opts, errp);
     if (ret < 0) {
@@ -575,6 +587,25 @@ fail:
     bdrv_unref(bs);
     qapi_free_QCryptoBlockCreateOptions(create_opts);
     qobject_unref(cryptoopts);
+
+    /*
+     * If an error occurred and we ended up creating a bogus
+     * 'filename' file, delete it
+     */
+    if (ret && !file_already_existed && bdrv_path_is_regular_file(path)) {
+        Error *local_err;
+        int r_del = bdrv_delete_file(path, &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: ", path);
+        }
+    }
+
     return ret;
 }
 
-- 
2.20.1