From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Daniel Sneddon <daniel.sneddon@linux.intel.com>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Alexandre Chartre <alexandre.chartre@oracle.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Peter Zijlstra <peterz@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Sean Christopherson <seanjc@google.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Nikolay Borisov <nik.borisov@suse.com>,
KP Singh <kpsingh@kernel.org>, Waiman Long <longman@redhat.com>,
Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH 5/7] x86/bugs: Only harden syscalls when needed
Date: Fri, 12 Apr 2024 11:24:53 +0100 [thread overview]
Message-ID: <323fbfe5-ad21-4606-93c7-d3ad6bbc8620@citrix.com> (raw)
In-Reply-To: <20240411153841.zexbsqrdli54kiez@treble>
On 11/04/2024 4:38 pm, Josh Poimboeuf wrote:
> On Thu, Apr 11, 2024 at 11:06:37AM +0100, Andrew Cooper wrote:
>>> +#define __do_syscall(table, func_direct, nr, regs) \
>>> +({ \
>>> + unsigned long __rax, __rdi, __rsi; \
>>> + \
>>> + asm_inline volatile( \
>>> + ALTERNATIVE("call " __stringify(func_direct) "\n\t", \
>>> + ANNOTATE_RETPOLINE_SAFE \
>>> + "call *%[func_ptr]\n\t", \
>> This wants to be a plain maybe-thunk'd indirect call, and without the
>> ANNOTATE_RETPOLINE_SAFE.
>>
>> Or you're going to get into cases where some combinations of command
>> line options do unexpected things e.g. retpolining everything except the
>> syscall dispatch.
> In that case won't X86_FEATURE_INDIRECT_SAFE get cleared, resulting in
> the above using a direct call? Or did I miss something?
That works until the next time anyone touches the logic. Then it's
latent vulnerability, or an incorrect trial of a non-default option.
I guarantee you'll save someone (probably someone on this CC list) a
headache in the future by not introducing an unnecessary special case here.
~Andrew
next prev parent reply other threads:[~2024-04-12 10:24 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-11 5:40 [PATCH 0/7] x86/bugs: BHI fixes / improvements Josh Poimboeuf
2024-04-11 5:40 ` [PATCH 1/7] x86/bugs: BHI documentation fixes Josh Poimboeuf
2024-04-11 6:21 ` Nikolay Borisov
2024-04-11 8:40 ` [tip: x86/urgent] x86/bugs: Fix BHI documentation tip-bot2 for Josh Poimboeuf
2024-04-11 5:40 ` [PATCH 2/7] x86/bugs: Cache the value of MSR_IA32_ARCH_CAPABILITIES Josh Poimboeuf
2024-04-11 6:22 ` Nikolay Borisov
2024-04-11 7:32 ` [PATCH 2b/7] x86/bugs: Rename various 'ia32_cap' variables to 'x86_arch_cap_msr' Ingo Molnar
2024-04-11 8:40 ` [tip: x86/urgent] x86/bugs: Cache the value of MSR_IA32_ARCH_CAPABILITIES tip-bot2 for Josh Poimboeuf
2024-04-11 8:40 ` [tip: x86/urgent] x86/bugs: Rename various 'ia32_cap' variables to 'x86_arch_cap_msr' tip-bot2 for Ingo Molnar
2024-04-11 5:40 ` [PATCH 3/7] x86/bugs: Fix BHI handling of RRSBA Josh Poimboeuf
2024-04-11 8:40 ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
2024-04-11 10:02 ` [PATCH 3/7] " Andrew Cooper
2024-04-11 15:34 ` Josh Poimboeuf
2024-04-11 5:40 ` [PATCH 4/7] x86/bugs: Clarify that syscall hardening isn't a BHI mitigation Josh Poimboeuf
2024-04-11 8:40 ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
2024-04-11 5:40 ` [PATCH 5/7] x86/bugs: Only harden syscalls when needed Josh Poimboeuf
2024-04-11 6:20 ` Nikolay Borisov
2024-04-11 15:08 ` Josh Poimboeuf
2024-04-11 8:40 ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
2024-04-11 10:06 ` [PATCH 5/7] " Andrew Cooper
2024-04-11 15:38 ` Josh Poimboeuf
2024-04-12 10:24 ` Andrew Cooper [this message]
2024-04-12 0:15 ` Pawan Gupta
2024-04-12 3:57 ` Josh Poimboeuf
2024-04-12 4:17 ` Josh Poimboeuf
2024-04-12 5:20 ` Josh Poimboeuf
2024-04-12 10:36 ` Andrew Cooper
2024-04-12 20:24 ` Josh Poimboeuf
2024-04-12 5:27 ` Pawan Gupta
2024-04-12 10:07 ` Ingo Molnar
2024-04-12 6:28 ` Pawan Gupta
2024-04-12 6:37 ` Pawan Gupta
2024-04-11 5:40 ` [PATCH 6/7] x86/bugs: Remove CONFIG_BHI_MITIGATION_AUTO and spectre_bhi=auto Josh Poimboeuf
2024-04-11 6:23 ` Nikolay Borisov
2024-04-11 8:40 ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
2024-04-12 10:12 ` tip-bot2 for Josh Poimboeuf
2024-04-11 5:40 ` [PATCH 7/7] x86/bugs: Replace CONFIG_SPECTRE_BHI_{ON,OFF} with CONFIG_MITIGATION_SPECTRE_BHI Josh Poimboeuf
2024-04-11 7:48 ` Ingo Molnar
2024-04-11 8:18 ` Ingo Molnar
2024-04-17 5:35 ` Reinette Chatre
2024-04-11 15:24 ` Josh Poimboeuf
2024-04-11 8:40 ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
2024-04-12 10:12 ` tip-bot2 for Josh Poimboeuf
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