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Re: [Qemu-block] [Qemu-devel] [PATCH 1/1] block_crypto_co_create_generic

From: Daniel Henrique Barboza
Subject: Re: [Qemu-block] [Qemu-devel] [PATCH 1/1] block_crypto_co_create_generic: clean up created file on failure
Date: Wed, 20 Mar 2019 09:03:27 -0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0

On 3/20/19 6:52 AM, Daniel P. Berrangé wrote:
On Tue, Mar 19, 2019 at 07:03:30PM -0300, Daniel Henrique Barboza wrote:
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 
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 fixes it by adding a flag to indicate whether bdrv_create_file()
created the file, and then unlinking it in the 'fail' label if

* 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 <address@hidden>
Signed-off-by: Daniel Henrique Barboza <address@hidden>
  block/crypto.c | 9 +++++++++
  1 file changed, 9 insertions(+)

diff --git a/block/crypto.c b/block/crypto.c
index fd8c7cfac6..5b43424845 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -533,6 +533,7 @@ static int coroutine_fn 
block_crypto_co_create_opts_luks(const char *filename,
      BlockDriverState *bs = NULL;
      QDict *cryptoopts;
      int64_t size;
+    bool filecreated = false;
      int ret;
/* Parse options */
@@ -554,6 +555,7 @@ static int coroutine_fn 
block_crypto_co_create_opts_luks(const char *filename,
      if (ret < 0) {
          goto fail;
+    filecreated = true;
bs = bdrv_open(filename, NULL, NULL,
                     BDRV_O_RDWR | BDRV_O_RESIZE | BDRV_O_PROTOCOL, errp);
@@ -569,7 +571,14 @@ static int coroutine_fn 
block_crypto_co_create_opts_luks(const char *filename,
ret = 0;
+    goto cleanup;
+    if (filecreated) {
+        unlink(filename);
You can't do this I'm afraid.

"filename" cannot be assumed to be a local file - it can be an arbitrary
block device backend string.

Contrary to what you might expect, given the call to bdrv_create_file,
we can't actually assume this method created the file either. The above
bdrv_create_file method may have merely formatted a pre-existing volume.

To fix this requires a "bdrv_delete" callback in the BlockDriver code,
and the actual deletion would need to be done in the "qemu-img create"

Thanks for the pointers. I'll see if I can make this happen in v2.



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