From: Dave Hansen <dave.hansen@intel.com>
To: Andrey Zakharov <dedemorow@gmail.com>, x86@kernel.org
Cc: Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
hpa@zytor.com, Peter Zijlstra <peterz@infradead.org>,
Kees Cook <kees@kernel.org>, Brian Gerst <brgerst@gmail.com>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/entry/32: Harden return-to-user
Date: Tue, 27 Oct 2026 15:01:35 -0700 [thread overview]
Message-ID: <ac147f25-a2d3-46b9-89c5-44a1c0e4f038@intel.com> (raw)
In-Reply-To: <20261027215251.15275-1-dedemorow@gmail.com>
On 10/27/26 14:52, Andrey Zakharov wrote:
> --- a/arch/x86/entry/entry_32.S
> +++ b/arch/x86/entry/entry_32.S
> @@ -952,6 +952,14 @@ restore_all_switch_stack:
>
> /* Restore user state */
> RESTORE_REGS pop=4 # skip orig_eax/error_code
> +
> + /* Assert that the IRET frame returns to user mode or vm86. */
> + testb $USER_SEGMENT_RPL_MASK, 4(%esp)
> + jnz .Lreturn_to_user_ok
> + testl $X86_EFLAGS_VM, 8(%esp)
> + jnz .Lreturn_to_user_ok
> + ud2
> +.Lreturn_to_user_ok:
I'm curious who cares.
Is anyone who is actually still running a 32-bit kernel concerned about
this kind of hardening?
If no one cares, then I'd rather pass on the complexity, even four
instructions of it.
next prev parent reply other threads:[~2026-10-27 22:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-27 21:52 Andrey Zakharov
2026-10-27 22:01 ` Dave Hansen [this message]
2026-10-28 19:21 ` s1nkhole
2026-10-28 20:40 ` Borislav Petkov
2026-10-28 20:50 ` Dave Hansen
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