linux-kernel - Re: Re [PATCH v5 4/5] x86/pkeys: Restore altstack before sigcontext

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Date: Tue, 11 Jun 2024 14:08:26 +0000
From: Aruna Ramakrishna <aruna.ramakrishna@...cle.com>
To: "jeffxu@...omium.org" <jeffxu@...omium.org>
CC: "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        Keith Lucas
	<keith.lucas@...cle.com>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>, Thomas
 Gleixner <tglx@...utronix.de>,
        "x86@...nel.org" <x86@...nel.org>,
        Andrew
 Brownsword <andrew.brownsword@...cle.com>,
        Matthias Neugschwandtner
	<matthias.neugschwandtner@...cle.com>,
        "jeffxu@...gle.com"
	<jeffxu@...gle.com>,
        "jannh@...gle.com" <jannh@...gle.com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "sroettger@...gle.com"
	<sroettger@...gle.com>,
        "jorgelo@...omium.org" <jorgelo@...omium.org>,
        "rick.p.edgecombe@...el.com" <rick.p.edgecombe@...el.com>
Subject: Re: Re [PATCH v5 4/5] x86/pkeys: Restore altstack before sigcontext

> On Jun 10, 2024, at 2:44 PM, jeffxu@...omium.org wrote:
> 
> Can we we move this patch to the first of the series? this can be an
> independent patch, the problem not only affect PKRU, but also other
> scenarios, as Rick pointed out in [1]
> 
> [1] https://lore.kernel.org/lkml/d0162c76c25bc8e1c876aebe8e243ff2e6862359.camel@intel.com/
> 
> -Jeff

For this patch set, the issue with rt_sigreturn() is only exposed after patch 3/5 - i.e., when
copy_fpregs_to_sigframe() calls update_pkru_in_sigframe() to update the PKRU value to
user-specified PKRU that might disable pkey 0 access, thus breaking restore_altstack().
So it seemed logical to me to have this fix as patch 4/5 of this series. I’m not strongly
opposed to moving this to patch 1/5, but this ordering is easier to understand (I think).
But if this patch needs to be broken out of this patchset and submitted independently
(for the other scenarios you mentioned) - I can do that.

Thanks,
Aruna