Re: [libvirt] [PATCH v2 0/2] ESX: Fixing SetAutoStart

2018-08-02 18:16 GMT+02:00 John Ferlan <jferlan(a)redhat.com&gt;: > > > On 08/02/2018 12:11 PM, Marcos Paulo de Souza wrote: >> 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&gt;: >>>> >>>> >>>> On 08/02/2018 10:07 AM, Matthias Bolte wrote: >>>>> 2018-08-02 15:20 GMT+02:00 John Ferlan <jferlan(a)redhat.com&gt;: >>>>>> >>>>>> >>>>>> 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&gt;: >>>>>>>> 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&gt; >>> 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&gt; >>> --- >>> 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&gt; >> > > Reviewed-by: John Ferlan <jferlan(a)redhat.com&gt; > > 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 > Thanks and pushed. -- Matthias Bolte http://photron.blogspot.com