On Thu, Aug 02, 2018 at 05:37:46PM +0200, Matthias Bolte wrote:
> 2018-08-02 16:45 GMT+02:00 John Ferlan <jferlan(a)redhat.com>:
>>
>>
>> On 08/02/2018 10:07 AM, Matthias Bolte wrote:
>>> 2018-08-02 15:20 GMT+02:00 John Ferlan <jferlan(a)redhat.com>:
>>>>
>>>>
>>>> On 08/02/2018 05:04 AM, Matthias Bolte wrote:
>>>>> 2018-08-01 18:09 GMT+02:00 Marcos Paulo de Souza
<marcos.souza.org(a)gmail.com>:
>>>>>> This is a new version from the last patchset sent yesterday, but
now using
>>>>>> VIR_STRNDUP, instead of allocating memory manually.
>>>>>>
>>>>>> First version:
https://www.redhat.com/archives/libvir-list/2018-August/msg00000.html
>>>>>>
>>>>>> Marcos Paulo de Souza (2):
>>>>>> esx: Do not crash SetAutoStart by double free
>>>>>> esx: Fix SetAutoStart invalid pointer free
>>>>>>
>>>>>> src/esx/esx_driver.c | 14 +++++++++++---
>>>>>> 1 file changed, 11 insertions(+), 3 deletions(-)
>>>>>
>>>>> I see the problem, but your approach is too complicated.
>>>>>
>>>>> There is already code in place to handle those situations:
>>>>>
>>>>> 3417 cleanup:
>>>>> 3418 if (newPowerInfo) {
>>>>> 3419 newPowerInfo->key = NULL;
>>>>> 3420 newPowerInfo->startAction = NULL;
>>>>> 3421 newPowerInfo->stopAction = NULL;
>>>>> 3422 }
>>>>>
>>>>> That resets those fields to NULL to avoid double freeing and freeing
>>>>> static strings.
>>>>>
>>>>> The problem is that commit ae83e02f3dd7fe99fed5d8159a35b666fafeafd5
by
>>>>> John Frelan broke this logic, by setting newPowerInfo to NULL in the
>>>>> success path, to silence Coverity.
>>>>>
>>>>
>>>> Memory recall from "Tue Sep 3 07:20:34 2013 -0400" is perhaps
impossible
>>>> ;-)... TL;DR, looks like the error back then was a false positive
>>>> because (as I know I've learned since then) Coverity has a hard time
>>>> when a boolean or size_t count is used to control whether or not memory
>>>> would be freed.
>>>>
>>>> Looking at the logic:
>>>>
>>>> if (esxVI_AutoStartPowerInfo_AppendToList(&spec->powerInfo,
>>>> newPowerInfo) < 0) {
>>>> goto cleanup;
>>>> }
>>>>
>>>> newPowerInfo = NULL;
>>>>
>>>> and following it to esxVI_List_Append which on success would seemingly
>>>> assign @newPowerInfo into the &spec->powerInfo list, I can
certainly see
>>>> why logically setting newPowerInfo = NULL after than would seem to be
>>>> the right thing. Of course, I see now the subtle reason why it's not
a
>>>> good idea.
>>>>
>>>> Restoring logic from that commit in esxDomainSetAutostart, then Coverity
>>>> believes that @newPowerInfo is leaked from the goto cleanup at
>>>> allocation because for some reason it has decided it must evaluate both
>>>> true and false of a condition even though the logic only ever set the
>>>> boolean when @newPowerInfo was placed onto the @spec->powerInfo list.
>>>> IOW: A false positive because the human can read the code and say that
>>>> Coverity is full of it.
>>>>
>>>> So either I add this to my Coverity list of false positives or in the
>>>> "if (esxVI_AutoStartPowerInfo_Alloc(&newPowerInfo) < 0 ||
" condition
>>>> cleanup logic call esxVI_AutoStartPowerInfo_Free(&newPowerInfo);
prior
>>>> to cleanup, removing it from the cleanup: path, and then remove the
>>>> "newPowerInfo = NULL;" after list insertion.
>>>>
>>>> <sigh>
>>>>
>>>> John
>>>
>>> Okay, I see what's going on. I suggest this alternative patch that
>>> keeps the newPowerInfo = NULL line to make Coverity understand the
>>> cleanup code, but adds a second variable to restore the original
>>> logic. I hope this doesn't upset Coverity.
>>>
>>> Marcos, can you give the attached patch a try? It should fix the
>>> problems you try to fix here, by restoring the original cleanup logic.
>>>
>>
>> That patch was confusing at best... The following works just fine:
>>
>> diff --git a/src/esx/esx_driver.c b/src/esx/esx_driver.c
>> index cee98ebcaf..a3982089e3 100644
>> --- a/src/esx/esx_driver.c
>> +++ b/src/esx/esx_driver.c
>> @@ -3387,6 +3387,8 @@ esxDomainSetAutostart(virDomainPtr domain, int autostart)
>> esxVI_Int_Alloc(&newPowerInfo->startOrder) < 0 ||
>> esxVI_Int_Alloc(&newPowerInfo->startDelay) < 0 ||
>> esxVI_Int_Alloc(&newPowerInfo->stopDelay) < 0) {
>> +
>> + esxVI_AutoStartPowerInfo_Free(&newPowerInfo);
>> goto cleanup;
>> }
>>
>> @@ -3403,8 +3405,6 @@ esxDomainSetAutostart(virDomainPtr domain, int autostart)
>> goto cleanup;
>> }
>>
>> - newPowerInfo = NULL;
>> -
>> if (esxVI_ReconfigureAutostart
>> (priv->primary,
>>
priv->primary->hostSystem->configManager->autoStartManager,
>> @@ -3426,8 +3426,6 @@ esxDomainSetAutostart(virDomainPtr domain, int autostart)
>> esxVI_AutoStartDefaults_Free(&defaults);
>> esxVI_AutoStartPowerInfo_Free(&powerInfoList);
>>
>> - esxVI_AutoStartPowerInfo_Free(&newPowerInfo);
>> -
>> return result;
>> }
>>
>>
>> A comment could be added that indicates by moving the *_Free to cleanup:
>> along with the setting of newPowerInfo = NULL after the AppendToList
>> caused issues with eventual esxVI_HostAutoStartManagerConfig_Free trying
>> to VIR_FREE static strings and double freeing the machine object.
>>
>> John
>
> Your approach works, but it doesn't handle the
> esxVI_AutoStartPowerInfo_AppendToList cleanup case in which
> key/startAction/stopAction have to be unset and
> esxVI_AutoStartPowerInfo_Free(&newPowerInfo) has to be called because
> the list failed to take ownership of the newPowerInfo object and
> esxVI_HostAutoStartManagerConfig_Free will not free it in this case.
>
> Based on your suggestion here's a modified patch for this.
>
> --
> Matthias Bolte
>
http://photron.blogspot.com
> From 090cf89ca6d8966fccf6cf6110ac8dc0b79865a8 Mon Sep 17 00:00:00 2001
> From: Matthias Bolte <matthias.bolte(a)googlemail.com>
> Date: Thu, 2 Aug 2018 17:33:37 +0200
> Subject: [PATCH] esx: Fix double-free and freeing static strings in
> esxDomainSetAutostart
>
> Since commit ae83e02f3dd7fe99fed5d8159a35b666fafeafd5#l3393 the
> newPowerInfo pointer itself is used to track the ownership of the
> AutoStartPowerInfo object to make Coverity understand the code better.
> This broke the code that unset some members of the AutoStartPowerInfo
> object that should not be freed the normal way.
>
> Instead, transfer ownership of the AutoStartPowerInfo object to the
> HostAutoStartManagerConfig object before filling in the values that
> need special handling. This allows to free the AutoStartPowerInfo
> directly without having to deal with the special values, or to let
> the old (now restored) logic handle the special values again.
>
> Signed-off-by: Matthias Bolte <matthias.bolte(a)googlemail.com>
> ---
> src/esx/esx_driver.c | 14 ++++----------
> 1 file changed, 4 insertions(+), 10 deletions(-)
>
> diff --git a/src/esx/esx_driver.c b/src/esx/esx_driver.c
> index cee98ebcaf..c2154799fa 100644
> --- a/src/esx/esx_driver.c
> +++ b/src/esx/esx_driver.c
> @@ -3386,7 +3386,10 @@ esxDomainSetAutostart(virDomainPtr domain, int autostart)
> if (esxVI_AutoStartPowerInfo_Alloc(&newPowerInfo) < 0 ||
> esxVI_Int_Alloc(&newPowerInfo->startOrder) < 0 ||
> esxVI_Int_Alloc(&newPowerInfo->startDelay) < 0 ||
> - esxVI_Int_Alloc(&newPowerInfo->stopDelay) < 0) {
> + esxVI_Int_Alloc(&newPowerInfo->stopDelay) < 0 ||
> + esxVI_AutoStartPowerInfo_AppendToList(&spec->powerInfo,
> + newPowerInfo) < 0) {
> + esxVI_AutoStartPowerInfo_Free(&newPowerInfo);
> goto cleanup;
> }
>
> @@ -3398,13 +3401,6 @@ esxDomainSetAutostart(virDomainPtr domain, int autostart)
> newPowerInfo->stopDelay->value = -1; /* use system default */
> newPowerInfo->stopAction = (char *)"none";
>
> - if (esxVI_AutoStartPowerInfo_AppendToList(&spec->powerInfo,
> - newPowerInfo) < 0) {
> - goto cleanup;
> - }
> -
> - newPowerInfo = NULL;
> -
> if (esxVI_ReconfigureAutostart
> (priv->primary,
> priv->primary->hostSystem->configManager->autoStartManager,
> @@ -3426,8 +3422,6 @@ esxDomainSetAutostart(virDomainPtr domain, int autostart)
> esxVI_AutoStartDefaults_Free(&defaults);
> esxVI_AutoStartPowerInfo_Free(&powerInfoList);
>
> - esxVI_AutoStartPowerInfo_Free(&newPowerInfo);
> -
> return result;
> }
>
> --
> 2.14.1
>
It worked in ESXi server. So:
Tested-by: Marcos Paulo de Souza <marcos.souza.org(a)gmail.com>
Reviewed-by: John Ferlan <jferlan(a)redhat.com>
and safe for freeze (you have commit rights, so I'll let you push).
Also checked w/ my coverity build and no issue from there.
John