[07/16] block/qcow2-bitmap: Fix missing ERRP_GUARD() for error_prepend()

Commit Message

Zhao Liu Feb. 28, 2024, 4:37 p.m. UTC

From: Zhao Liu <[e-mail]>

As the comment in qapi/error, passing @errp to error_prepend() requires
ERRP_GUARD():

* = Why, when and how to use ERRP_GUARD() =
*
* Without ERRP_GUARD(), use of the @errp parameter is restricted:
...
* - It should not be passed to error_prepend(), error_vprepend() or
*   error_append_hint(), because that doesn't work with &error_fatal.
* ERRP_GUARD() lifts these restrictions.
*
* To use ERRP_GUARD(), add it right at the beginning of the function.
* @errp can then be used without worrying about the argument being
* NULL or &error_fatal.

ERRP_GUARD() could avoid the case when @errp is the pointer of
error_fatal, the user can't see this additional information, because
exit() happens in error_setg earlier than information is added [1].

The qcow2_co_can_store_new_dirty_bitmap() passes @errp to
error_prepend(). As a BlockDriver.bdrv_co_can_store_new_dirty_bitmap
method, it's called by bdrv_co_can_store_new_dirty_bitmap().

Its caller is not being called anywhere, but as the API in
include/block/block-io.h, we can't ensure what kind of @errp future
users will pass in.

To avoid potential issues as [1] said, add missing ERRP_GUARD() at the
beginning of qcow2_co_can_store_new_dirty_bitmap().

[1]: Issue description in the commit message of commit ae7c80a7bd73
     ("error: New macro ERRP_GUARD()").

Cc: Eric Blake <[e-mail]>
Cc: Vladimir Sementsov-Ogievskiy <[e-mail]>
Cc: John Snow <[e-mail]>
Cc: Kevin Wolf <[e-mail]>
Cc: Hanna Reitz <[e-mail]>
Signed-off-by: Zhao Liu <[e-mail]>
---
 block/qcow2-bitmap.c | 1 +
 1 file changed, 1 insertion(+)

Comments

Vladimir Sementsov-Ogievskiy Feb. 28, 2024, 4:32 p.m. UTC | #1

On 28.02.24 19:37, Zhao Liu wrote:
> From: Zhao Liu<[e-mail]>
> 
> As the comment in qapi/error, passing @errp to error_prepend() requires
> ERRP_GUARD():
> 
> * = Why, when and how to use ERRP_GUARD() =
> *
> * Without ERRP_GUARD(), use of the @errp parameter is restricted:
> ...
> * - It should not be passed to error_prepend(), error_vprepend() or
> *   error_append_hint(), because that doesn't work with &error_fatal.
> * ERRP_GUARD() lifts these restrictions.
> *
> * To use ERRP_GUARD(), add it right at the beginning of the function.
> * @errp can then be used without worrying about the argument being
> * NULL or &error_fatal.
> 
> ERRP_GUARD() could avoid the case when @errp is the pointer of
> error_fatal, the user can't see this additional information, because
> exit() happens in error_setg earlier than information is added [1].
> 
> The qcow2_co_can_store_new_dirty_bitmap() passes @errp to
> error_prepend(). As a BlockDriver.bdrv_co_can_store_new_dirty_bitmap
> method, it's called by bdrv_co_can_store_new_dirty_bitmap().
> 
> Its caller is not being called anywhere, but as the API in
> include/block/block-io.h, we can't ensure what kind of @errp future
> users will pass in.
> 
> To avoid potential issues as [1] said, add missing ERRP_GUARD() at the
> beginning of qcow2_co_can_store_new_dirty_bitmap().
> 
> [1]: Issue description in the commit message of commit ae7c80a7bd73
>       ("error: New macro ERRP_GUARD()").
> 
> Cc: Eric Blake<[e-mail]>
> Cc: Vladimir Sementsov-Ogievskiy<[e-mail]>
> Cc: John Snow<[e-mail]>
> Cc: Kevin Wolf<[e-mail]>
> Cc: Hanna Reitz<[e-mail]>
> Signed-off-by: Zhao Liu<[e-mail]>

Reviewed-by: Vladimir Sementsov-Ogievskiy <[e-mail]>

Patch

diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
index 0e567ed588d7..874ea5694851 100644
--- a/block/qcow2-bitmap.c
+++ b/block/qcow2-bitmap.c
@@ -1710,6 +1710,7 @@  bool coroutine_fn qcow2_co_can_store_new_dirty_bitmap(BlockDriverState *bs,
                                                       uint32_t granularity,
                                                       Error **errp)
 {
+    ERRP_GUARD();
     BDRVQcow2State *s = bs->opaque;
     BdrvDirtyBitmap *bitmap;
     uint64_t bitmap_directory_size = 0;