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block/qcow2: Fix missing ERRP_GUARD() for error_prepend() 

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 &error_fatal, the user
can't see this additional information, because exit() happens in
error_setg earlier than information is added [1].

In block/qcow2.c, there are 2 functions passing @errp to error_prepend()
without ERRP_GUARD():
 - qcow2_co_create()
 - qcow2_co_truncate()

There are too many possible callers to check the impact of the defect;
it may or may not be harmless. Thus it is necessary to protect @errp with
ERRP_GUARD().

Therefore, to avoid the issue like [1] said, add missing ERRP_GUARD() at
their beginning.

[1]: Issue description in the commit message of commit ae7c80a7bd
     ("error: New macro ERRP_GUARD()").

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Hanna Reitz <hreitz@redhat.com>
Cc: qemu-block@nongnu.org
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-ID: <20240311033822.3142585-9-zhao1.liu@linux.intel.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
master
Zhao Liu 2024-03-11 11:38:01 +08:00 committed by Thomas Huth
parent e1081e3bff
commit d13e3b4670
1 changed files with 2 additions and 0 deletions
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2
block/qcow2.c
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@ -3483,6 +3483,7 @@ static uint64_t qcow2_opt_get_refcount_bits_del(QemuOpts *opts, int version,
static int coroutine_fn GRAPH_UNLOCKED
qcow2_co_create(BlockdevCreateOptions *create_options, Error **errp)
{
ERRP_GUARD();
BlockdevCreateOptionsQcow2 *qcow2_opts;
QDict *options;
@ -4283,6 +4284,7 @@ static int coroutine_fn GRAPH_RDLOCK
qcow2_co_truncate(BlockDriverState *bs, int64_t offset, bool exact,
PreallocMode prealloc, BdrvRequestFlags flags, Error **errp)
{
ERRP_GUARD();
BDRVQcow2State *s = bs->opaque;
uint64_t old_length;
int64_t new_l1_size;