[PATCH v2 0/2] crypto: fix handling & reporting of errors when erasing keyslots

[PATCH v2 0/2] crypto: fix handling & reporting of errors when erasing keyslots

[Daniel P. Berrangé]

Changed in v2:

 - Simplify first patch to rely error_propagate auto
   discarding dupe errors.

Daniel P. Berrangé (2):
  crypto: avoid overwriting Error object erasing keyslot
  crypto: add newline in error hint messages

 crypto/block-luks.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

-- 
2.56.0

[PATCH v2 1/2] crypto: avoid overwriting Error object erasing keyslot

[Daniel P. Berrangé]

When erasing a keyslot we deliberately ignore some errors and
carry on trying to erase as much as possible. This results in
overwriting Error objects and triggering an assertion. Don't
pass in the &local_err, if errp is already set.

Fixes: https://gitlab.com/qemu-project/qemu/-/work_items/4697
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 crypto/block-luks.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/crypto/block-luks.c b/crypto/block-luks.c
index 0926ad28f0c..277a5110607 100644
--- a/crypto/block-luks.c
+++ b/crypto/block-luks.c
@@ -1152,6 +1152,7 @@ qcrypto_block_luks_erase_key(QCryptoBlock *block,
 
     if (ret < 0) {
         error_propagate(errp, local_err);
+        local_err = NULL;
     }
     /*
      * Now try to erase the key material, even if the header
@@ -1169,6 +1170,7 @@ qcrypto_block_luks_erase_key(QCryptoBlock *block,
             if (i > 0) {
                 return -1;
             }
+            local_err = NULL;
         }
         if (writefunc(block,
                       slot->key_offset_sector * QCRYPTO_BLOCK_LUKS_SECTOR_SIZE,
-- 
2.56.0

Re: [PATCH v2 1/2] crypto: avoid overwriting Error object erasing keyslot

[Markus Armbruster]

Daniel P. Berrangé <berrange@redhat.com> writes:

> When erasing a keyslot we deliberately ignore some errors and
> carry on trying to erase as much as possible. This results in
> overwriting Error objects and triggering an assertion. Don't
> pass in the &local_err, if errp is already set.
>
> Fixes: https://gitlab.com/qemu-project/qemu/-/work_items/4697
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  crypto/block-luks.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/crypto/block-luks.c b/crypto/block-luks.c
> index 0926ad28f0c..277a5110607 100644
> --- a/crypto/block-luks.c
> +++ b/crypto/block-luks.c
> @@ -1152,6 +1152,7 @@ qcrypto_block_luks_erase_key(QCryptoBlock *block,
   {
       QCryptoBlockLUKS *luks = block->opaque;
       QCryptoBlockLUKSKeySlot *slot;
       g_autofree uint8_t *garbagesplitkey = NULL;
       size_t splitkeylen;
       size_t i;
       Error *local_err = NULL;
       int ret;

       assert(slot_idx < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS);
       slot = &luks->header.key_slots[slot_idx];

       splitkeylen = luks->header.master_key_len * slot->stripes;
       assert(splitkeylen > 0);

       garbagesplitkey = g_new0(uint8_t, splitkeylen);

       /* Reset the key slot header */
       memset(slot->salt, 0, QCRYPTO_BLOCK_LUKS_SALT_LEN);
       slot->iterations = 0;
       slot->active = QCRYPTO_BLOCK_LUKS_KEY_SLOT_DISABLED;

       ret = qcrypto_block_luks_store_header(block, writefunc,
                                             opaque, &local_err);

Why not pass @errp here, and ...

>  
>      if (ret < 0) {
>          error_propagate(errp, local_err);

... drop this line?

> +        local_err = NULL;
>      }

Suggest a blank line here.


Note for later: @errp may be non-null now.

>      /*
>       * Now try to erase the key material, even if the header
> @@ -1169,6 +1170,7 @@ qcrypto_block_luks_erase_key(QCryptoBlock *block,
        * update failed
        */
       for (i = 0; i < QCRYPTO_BLOCK_LUKS_ERASE_ITERATIONS; i++) {
           if (qcrypto_random_bytes(garbagesplitkey,
                                    splitkeylen, &local_err) < 0) {
               /*
                * If we failed to get the random data, still write
                * at least zeros to the key slot at least once
                */
               error_propagate(errp, local_err);

If @errp is still null, store this error, else ignore it.

>              if (i > 0) {
>                  return -1;

Stop when erasing non-first key slot failed.

>              }
> +            local_err = NULL;
>          }
>          if (writefunc(block,
>                        slot->key_offset_sector * QCRYPTO_BLOCK_LUKS_SECTOR_SIZE,
                         garbagesplitkey,
                         splitkeylen,
                         opaque,
                         &local_err) < 0) {
               error_propagate(errp, local_err);

We do need error_propagate() here, because @errp can be non-null.

               return -1;
           }
       }
       return ret;
   }

Nothing is wrong, so
Reviewed-by: Markus Armbruster <armbru@redhat.com>

Re: [PATCH v2 1/2] crypto: avoid overwriting Error object erasing keyslot

[marcandre.lureau]

> When erasing a keyslot we deliberately ignore some errors and
> carry on trying to erase as much as possible. This results in
> overwriting Error objects and triggering an assertion. Don't
> pass in the &local_err, if errp is already set.
> 
> Fixes: https://gitlab.com/qemu-project/qemu/-/work_items/4697
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> Message-ID: <20261026111237.660633-2-berrange@redhat.com>
> ---
>  crypto/block-luks.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/crypto/block-luks.c b/crypto/block-luks.c
> index 0926ad28f0cd..277a51106072 100644
> --- a/crypto/block-luks.c
> +++ b/crypto/block-luks.c
> @@ -1152,6 +1152,7 @@ qcrypto_block_luks_erase_key(QCryptoBlock *block,
>  
>      if (ret < 0) {
>          error_propagate(errp, local_err);
> +        local_err = NULL;
>      }
>      /*
>       * Now try to erase the key material, even if the header
> @@ -1169,6 +1170,7 @@ qcrypto_block_luks_erase_key(QCryptoBlock *block,
>              if (i > 0) {
>                  return -1;
>              }
> +            local_err = NULL;

This is the recoverable path: the comment says we still write zeros and
carry on, so a first-iteration random failure is not meant to be fatal. But
error_propagate(errp, local_err) has just stored that error in *errp.

Keep the first-iteration failure as non-fatal but do not hand it to errp?
(e.g. error_free(local_err) instead of error_propagate() when i == 0)

-- 
Marc-André Lureau <marcandre.lureau@redhat.com>

Re: [PATCH v2 1/2] crypto: avoid overwriting Error object erasing keyslot

[Daniel P. Berrangé]

On Tue, Oct 27, 2026 at 06:27:34PM +0400, marcandre.lureau@redhat.com wrote:
> > When erasing a keyslot we deliberately ignore some errors and
> > carry on trying to erase as much as possible. This results in
> > overwriting Error objects and triggering an assertion. Don't
> > pass in the &local_err, if errp is already set.
> > 
> > Fixes: https://gitlab.com/qemu-project/qemu/-/work_items/4697
> > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> > Message-ID: <20261026111237.660633-2-berrange@redhat.com>
> > ---
> >  crypto/block-luks.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/crypto/block-luks.c b/crypto/block-luks.c
> > index 0926ad28f0cd..277a51106072 100644
> > --- a/crypto/block-luks.c
> > +++ b/crypto/block-luks.c
> > @@ -1152,6 +1152,7 @@ qcrypto_block_luks_erase_key(QCryptoBlock *block,
> >  
> >      if (ret < 0) {
> >          error_propagate(errp, local_err);
> > +        local_err = NULL;
> >      }
> >      /*
> >       * Now try to erase the key material, even if the header
> > @@ -1169,6 +1170,7 @@ qcrypto_block_luks_erase_key(QCryptoBlock *block,
> >              if (i > 0) {
> >                  return -1;
> >              }
> > +            local_err = NULL;
> 
> This is the recoverable path: the comment says we still write zeros and
> carry on, so a first-iteration random failure is not meant to be fatal. But
> error_propagate(errp, local_err) has just stored that error in *errp.
> 
> Keep the first-iteration failure as non-fatal but do not hand it to errp?
> (e.g. error_free(local_err) instead of error_propagate() when i == 0)

From the POV of the caller, we always want to report an error back
to them. We just want to try todo as much erasing as possible, even
when we're reporting an error. So don't think of this as a recover
from error sucess path. It is still a fatal error overall.


With regards,
Daniel
-- 
|: https://berrange.com       ~~        https://hachyderm.io/@berrange :|
|: https://libvirt.org          ~~          https://entangle-photo.org :|
|: https://pixelfed.art/berrange   ~~    https://fstop138.berrange.com :|

[PATCH v2 2/2] crypto: add newline in error hint messages

[Daniel P. Berrangé]

The error_append_hint() API contract requires messages to end with
a newline character.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 crypto/block-luks.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/crypto/block-luks.c b/crypto/block-luks.c
index 277a5110607..f7217ad7b77 100644
--- a/crypto/block-luks.c
+++ b/crypto/block-luks.c
@@ -1674,7 +1674,7 @@ qcrypto_block_luks_amend_add_keyslot(QCryptoBlock *block,
 
     if (qcrypto_block_luks_find_key(block, old_password, master_key,
                                     readfunc, opaque, errp) < 0) {
-        error_append_hint(errp, "Failed to retrieve the master key");
+        error_append_hint(errp, "Failed to retrieve the master key\n");
         return -1;
     }
 
@@ -1687,7 +1687,7 @@ qcrypto_block_luks_amend_add_keyslot(QCryptoBlock *block,
     /* Now set the new keyslots */
     if (qcrypto_block_luks_store_key(block, keyslot, new_password, master_key,
                                      iter_time, writefunc, opaque, errp)) {
-        error_append_hint(errp, "Failed to write to keyslot %i", keyslot);
+        error_append_hint(errp, "Failed to write to keyslot %i\n", keyslot);
         return -1;
     }
     return 0;
@@ -1785,7 +1785,7 @@ qcrypto_block_luks_amend_erase_keyslots(QCryptoBlock *block,
 
         if (qcrypto_block_luks_erase_key(block, keyslot,
                                          writefunc, opaque, errp)) {
-            error_append_hint(errp, "Failed to erase keyslot %i", keyslot);
+            error_append_hint(errp, "Failed to erase keyslot %i\n", keyslot);
             return -1;
         }
 
@@ -1838,7 +1838,7 @@ qcrypto_block_luks_amend_erase_keyslots(QCryptoBlock *block,
             }
             if (qcrypto_block_luks_erase_key(block, i, writefunc,
                 opaque, errp)) {
-                error_append_hint(errp, "Failed to erase keyslot %zu", i);
+                error_append_hint(errp, "Failed to erase keyslot %zu\n", i);
                 return -1;
             }
         }
-- 
2.56.0

Re: [PATCH v2 2/2] crypto: add newline in error hint messages

[Markus Armbruster]

Daniel P. Berrangé <berrange@redhat.com> writes:

> The error_append_hint() API contract requires messages to end with
> a newline character.
>
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

Reviewed-by: Markus Armbruster <armbru@redhat.com>

Re: [PATCH v2 2/2] crypto: add newline in error hint messages

[marcandre.lureau]

On Mon, 26 Oct 2026 11:12:37 +0000, Daniel P. Berrangé <berrange@redhat.com> wrote:
> The error_append_hint() API contract requires messages to end with
> a newline character.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

-- 
Marc-André Lureau <marcandre.lureau@redhat.com>