[Pcsclite-muscle] Crash in SCardStatus

[Jonathan Verner]

Hi Ludovic,

(sorry for the second mail, the first one didn't go to the list, I am still getting used to this outlook webmail thingy)

> Sorry for the delay. Your email was in my gmail spam folder.

thanks for the response and no worries. Spam filters are too good these days :-)

> Are you able to reproduce the problem with pcsc-lite version 1.9.0?
> I ask because I fixed a race condition in SCardGetStatusChange() in
> version 1.8.24

I think I saw that change and tried with 1.9.0 already but I had some trouble with protocol mismatch between the app and pscd (although our software links libpscs-lite dynamically, so I don't see why) and gave up. I will try again and get back to the list with the results.

> For multiple threads be sure to read SCardEstablishContext() documentation

So, in principle, having a different scardcontext for each thread should be enough to keep the application thread safe? (In principle, because of course one can't rule out bugs :-))

Thanks again for your response!

Best,

Jonathan


Jonathan Verner, PhD.
software engineer

Nexus Group
Evropska 33/A
160 00 Praha 6
Czech Republic


Od: pcsclite-muscle <pcsclite-muscle-bounces at lists.infradead.org> za uživatele Ludovic Rousseau <ludovic.rousseau at gmail.com>
Odesláno: středa 2. prosince 2020 13:28
Komu: pcsclite-muscle at lists.infradead.org <pcsclite-muscle at lists.infradead.org>
Předmět: Re: [Pcsclite-muscle] Crash in SCardStatus 
 
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Le mar. 24 nov. 2020 à 13:28, Jonathan Verner
<jonathan.verner at nexusgroup.com> a écrit :
> Hello,

Hello Jonathan.

Sorry for the delay. Your email was in my gmail spam folder.

> I work for Nexus where we develop smartcard middleware and we use  libpcsc-lite. Recently, we have started seeing crashes on Linux (Ubuntu 18.04, which has libpcsc-lite version 1.8.23) when calling SCardStatus from our code. I suspect that the problem has to do with multiple threads calling into libpcsc-lite.
>
> In particular, the crash seems to happen when SCardStatus is called and, before it finishes, SCardDisconnect is called:
>
>    The crash happens in SCardStatus on line 1440 of winscard_clnt.c due to r (=pChannelMap->readerName)
>    no longer pointing to valid memory. My hypothesis is that, while calling getReaderStates on line 1434, a call to
>    SCardDisconnect arrives and frees the memory pointed to by pChannelMap->readerName.

Are you able to reproduce the problem with pcsc-lite version 1.9.0?
I ask because I fixed a race condition in SCardGetStatusChange() in
version 1.8.24
https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fludovicrousseau.blogspot.com%2F2018%2F10%2Fnew-version-of-pcsc-lite-1824.html&data=04%7C01%7Cjonathan.verner%40nexusgroup.com%7C4f3a2d7a08b449f995bb08d896bddc50%7C89f9cd6ffab54f61a85eb1b24768f7f6%7C1%7C0%7C637425089490812063%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=19QPMlV4Ub%2FlORyNZI8NaETEfNN1M%2F%2BSYhpb1QPUZY4%3D&reserved=0

> On the other hand, I am quite new to pcsc and perhaps my analysis is incorrect (I am attaching the logs I get from pcscd and pcsc-spy if someone would be willing to look at them).  Anyway, I wanted to know, if there is some documentation on how to safely call libpcsc-lite functions from multiple threads.

For multiple threads be sure to read SCardEstablishContext() documentation
https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpcsclite.apdu.fr%2Fapi%2Fgroup__API.html%23gaa1b8970169fd4883a6dc4a8f43f19b67&data=04%7C01%7Cjonathan.verner%40nexusgroup.com%7C4f3a2d7a08b449f995bb08d896bddc50%7C89f9cd6ffab54f61a85eb1b24768f7f6%7C1%7C0%7C637425089490812063%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=CfVh0AteqxQWdj8LgLQ1Z3czShBPzTlTzfAQaShGDg8%3D&reserved=0

Bye

--
 Dr. Ludovic Rousseau

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