On 07/25/2017 08:21 AM, Pavel Hrdina wrote:
On Tue, Jul 25, 2017 at 01:36:20PM +0200, Pavel Hrdina wrote:
> On Fri, Jul 14, 2017 at 10:04:41AM -0400, John Ferlan wrote:
>> Since the virSecretObjListAdd technically consumes @def on success,
>> the secretDefineXML should set @def = NULL immediately and process
>> the remaining calls using a new @objdef variable. We can use use
>> VIR_STEAL_PTR since we know the Add function just stores @def in
>> obj->def.
>>
>> This fixes a possible double free of @def if the code jumps to
>> restore_backup: and calls virSecretObjListRemove without setting
>> def = NULL. In this case, the subsequent call to DefFree would
>> succeed and free @def; however, the call to EndAPI would also
>> call DefFree because the Unref done would be the last one for
>> the @obj meaning the obj->def would be used to call DefFree,
>> but it's already been free'd because @def wasn't managed right
>> within this error path.
>>
>> Signed-off-by: John Ferlan <jferlan(a)redhat.com>
>> ---
>> src/secret/secret_driver.c | 19 ++++++++++---------
>> 1 file changed, 10 insertions(+), 9 deletions(-)
>>
>> diff --git a/src/secret/secret_driver.c b/src/secret/secret_driver.c
>> index 30124b4..77351d8 100644
>> --- a/src/secret/secret_driver.c
>> +++ b/src/secret/secret_driver.c
>> @@ -210,6 +210,7 @@ secretDefineXML(virConnectPtr conn,
>> {
>> virSecretPtr ret = NULL;
>> virSecretObjPtr obj = NULL;
>> + virSecretDefPtr objdef;
>
> s/objdef/objDef/
>
> Reviewed-by: Pavel Hrdina <phrdina(a)redhat.com>
Actually this patch introduces a memory leak in case we restore the
@backup definition.
virSecretObjListAdd() adds the @def into @obj and sets the old def
into @backup, so far good.
VIR_STEAL_PTR(objdef, def) leaves the @def == NULL, still good
But if we in any point jump to "restore_backup" after the VIR_STEAL_PTR
and the @backup != NULL we simply changes the @obj->def back to @backup
and the new def is only in @objdef which is not freed anywhere.
I went through this in the previous review, but for the opposite
condition where backup == NULL (repeated for ease)
Without the stealing of objdef, when return from the Add function we
have "refcnt=2" and "lock=true".
For some reason we jump to restore_backup and call ObjListRemove which
returns and the object refcnt=1 and lock=false.
We fall into cleanup:
Call virSecretDefFree(def) where @def != NULL, so it free's it
Call virSecretObjEndAPI(&obj) which calls Unref, setting R=0 and calling
virSecretDefFree(obj->def)... But wait, we already did that because we
allowed the DefFree(def) to free something it didn't own.
Possible fix is to set @def = NULL after the virSecretObjListRemove()
in restore_backup:
...
} else {
virSecretObjListRemove(driver->secrets, obj);
virObjectUnref(obj);
obj = NULL;
def = NULL;
}
...
The other fix to the leak you point out is:
if (backup) {
virSecretObjSetDef(obj, backup);
def = objdef;
} else {
virSecretObjListRemove(driver->secrets, obj);
}
and there is no need to have yet another @objdef.
Unless you want the other condition of having two free's of @def
Pavel
John