From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Eric Biggers <ebiggers3@gmail.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
David Howells <dhowells@redhat.com>,
Eric Biggers <ebiggers@google.com>,
"Serge E. Hallyn" <serge@hallyn.com>,
keyrings@vger.kernel.org, linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: [question] should 363b02dab09b3 be backported to stable 4.1+?
Date: Fri, 15 Dec 2017 14:08:22 +0900 [thread overview]
Message-ID: <20171215050822.GD11199@jagdpanzerIV> (raw)
In-Reply-To: <20171215035800.GA891@zzz.localdomain>
Hello Eric,
On (12/14/17 19:58), Eric Biggers wrote:
> Hi Sergey,
>
> On Fri, Dec 15, 2017 at 11:47:06AM +0900, Sergey Senozhatsky wrote:
> > Hello David, Eric,
> >
> > please help me out.
> >
> > I'm looking at 363b02dab09b ("KEYS: Fix race between updating and finding
> > a negative key") right now. So, I see that it has been backported to stable
> > 4.4+. My question is -- do we have those test_bit(KEY_FLAG_INSTANTIATED)
> > and test_bit(KEY_FLAG_NEGATIVE) races in stable 4.1?
> >
>
> Before 4.4 (146aa8b1453), ->reject_error was in union with ->type_data rather
> than ->payload, and no key types that used ->type_data implemented ->update().
> Therefore it was not possible to reproduce the crash.
>
> I do see there was another possible race, only theoretically a problem on
> architectures with weaker memory ordering than x86, where a key being negatively
> instantiated could be momentarily observed to be positively instantiated. But
> even then I don't see where it could be a real problem. (Note that most users
> wait for KEY_FLAG_USER_CONSTRUCT rather than checking KEY_FLAG_INSTANTIATED
> directly.)
thanks a ton. appreciate your help!
> You're free to backport the commit if you want to be absolutely sure, though I'd
> personally be more worried about other backports that might have been missed,
> and the bugs that haven't been found yet.
agreed.
-ss
prev parent reply other threads:[~2017-12-15 5:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-15 2:47 [question] should 363b02dab09b3 be backported to stable 4.1+? Sergey Senozhatsky
2017-12-15 3:58 ` Eric Biggers
2017-12-15 5:08 ` Sergey Senozhatsky [this message]
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