[PULL,14/55] block/qcow2: Fix missing ERRP_GUARD() for error_prepend()

Commit Message

Thomas Huth March 12, 2024, 12:42 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 &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 ae7c80a7bd73
     ("error: New macro ERRP_GUARD()").

Cc: Kevin Wolf <[e-mail]>
Cc: Hanna Reitz <[e-mail]>
Cc: [e-mail]
Signed-off-by: Zhao Liu <[e-mail]>
Reviewed-by: Eric Blake <[e-mail]>
Message-ID: <[e-mail]>
Signed-off-by: Thomas Huth <[e-mail]>
---
 block/qcow2.c | 2 ++
 1 file changed, 2 insertions(+)

Patch

diff --git a/block/qcow2.c b/block/qcow2.c
index 204f5854cf..956128b409 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -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;