From: "Arnd Bergmann" <arnd@arndb.de>
To: "Jason A . Donenfeld" <Jason@zx2c4.com>
Cc: "Florian Weimer" <fweimer@redhat.com>,
linux-kernel@vger.kernel.org, patches@lists.linux.dev,
"Thomas Gleixner" <tglx@linutronix.de>,
linux-crypto@vger.kernel.org, linux-api@vger.kernel.org,
x86@kernel.org, "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Adhemerval Zanella Netto" <adhemerval.zanella@linaro.org>,
"Carlos O'Donell" <carlos@redhat.com>,
"Christian Brauner" <brauner@kernel.org>
Subject: Re: [PATCH v10 3/4] random: introduce generic vDSO getrandom() implementation
Date: Wed, 30 Nov 2022 17:13:18 +0100 [thread overview]
Message-ID: <974d7fcb-efbb-4508-a4cb-4b5328669c14@app.fastmail.com> (raw)
In-Reply-To: <CAHmME9oGffi539nEAJkOjC-2yAR+0Ra+wQw5oG6Y6+CRr5e62g@mail.gmail.com>
On Wed, Nov 30, 2022, at 16:47, Jason A. Donenfeld wrote:
>> > There's padding at the end of the structure, yes. But both
>> > `generation` and `is_ready` will be at the same offset. If the
>> > structure grows, then sure, that'll have to be taken into account. But
>> > that's not a problem because this is a private implementation detail
>> > between the vdso code and the kernel.
>>
>> I was not concerned about incompatibility here, but rather about
>> possibly leaking kernel data to the vdso page.
>
> The vvar page starts out zeroed, no?
The typical problem is someone doing a copy_to_user() of an in-kernel
structure into the userspace side, which would then copy the
padding as well. If the source is on the stack, a malicious caller
can trick the another syscall into leaving sensitive data at this
exact stack location. Again, I'm not saying that your code is
vulnerable to that type of attack, just that making all ABI
structures not have holes is useful for auditing.
Arnd
next prev parent reply other threads:[~2022-11-30 16:13 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-29 21:06 [PATCH v10 0/4] implement getrandom() in vDSO Jason A. Donenfeld
2022-11-29 21:06 ` [PATCH v10 1/4] random: add vgetrandom_alloc() syscall Jason A. Donenfeld
2022-11-29 22:02 ` Thomas Gleixner
2022-11-30 0:59 ` Jason A. Donenfeld
2022-11-30 1:37 ` Thomas Gleixner
2022-11-30 1:42 ` Jason A. Donenfeld
2022-11-30 22:39 ` David Laight
2022-12-01 0:14 ` Jason A. Donenfeld
2022-11-30 10:51 ` Florian Weimer
2022-11-30 15:39 ` Jason A. Donenfeld
2022-11-30 16:38 ` Jason A. Donenfeld
2022-12-02 14:38 ` Jason A. Donenfeld
2022-12-01 2:16 ` Jason A. Donenfeld
2022-12-02 17:17 ` Florian Weimer
2022-12-02 18:29 ` Jason A. Donenfeld
2022-11-29 21:06 ` [PATCH v10 2/4] arch: allocate vgetrandom_alloc() syscall number Jason A. Donenfeld
2022-11-30 8:56 ` Geert Uytterhoeven
2022-11-30 10:06 ` Jason A. Donenfeld
2022-11-30 10:51 ` Arnd Bergmann
2022-11-29 21:06 ` [PATCH v10 3/4] random: introduce generic vDSO getrandom() implementation Jason A. Donenfeld
2022-11-29 22:42 ` Thomas Gleixner
2022-11-30 1:09 ` Jason A. Donenfeld
2022-11-30 10:44 ` Florian Weimer
2022-11-30 14:51 ` Jason A. Donenfeld
2022-11-30 14:59 ` Jason A. Donenfeld
2022-11-30 15:07 ` Arnd Bergmann
2022-11-30 15:12 ` Jason A. Donenfeld
2022-11-30 15:29 ` Arnd Bergmann
2022-11-30 15:47 ` Jason A. Donenfeld
2022-11-30 16:13 ` Arnd Bergmann [this message]
2022-11-30 16:40 ` Jason A. Donenfeld
2022-11-30 17:00 ` Thomas Gleixner
2022-11-29 21:06 ` [PATCH v10 4/4] x86: vdso: Wire up getrandom() vDSO implementation Jason A. Donenfeld
2022-11-29 22:52 ` Thomas Gleixner
2022-11-30 1:11 ` Jason A. Donenfeld
2022-11-30 5:22 ` Eric Biggers
2022-11-30 10:12 ` Jason A. Donenfeld
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