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Subject: Re: [PATCH RFC v9 4/7] x86/entry: Erase kernel stack in
 syscall_trace_enter()
To: Alexander Popov <alex.popov@linux.com>,
 kernel-hardening@lists.openwall.com, Kees Cook <keescook@chromium.org>,
 PaX Team <pageexec@freemail.hu>, Brad Spengler <spender@grsecurity.net>,
 Ingo Molnar <mingo@kernel.org>, Andy Lutomirski <luto@kernel.org>,
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 Ard Biesheuvel <ard.biesheuvel@linaro.org>, Borislav Petkov <bp@alien8.de>,
 Richard Sandiford <richard.sandiford@arm.com>,
 Thomas Gleixner <tglx@linutronix.de>, "H . Peter Anvin" <hpa@zytor.com>,
 Peter Zijlstra <a.p.zijlstra@chello.nl>, "Dmitry V . Levin"
 <ldv@altlinux.org>, Emese Revfy <re.emese@gmail.com>,
 Jonathan Corbet <corbet@lwn.net>, Andrey Ryabinin <aryabinin@virtuozzo.com>,
 "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
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 Al Viro <viro@zeniv.linux.org.uk>, "David S . Miller" <davem@davemloft.net>,
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 <dwmw@amazon.co.uk>, Josh Poimboeuf <jpoimboe@redhat.com>,
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References: <1520107232-14111-1-git-send-email-alex.popov@linux.com>
 <1520107232-14111-5-git-send-email-alex.popov@linux.com>
From: Dave Hansen <dave.hansen@linux.intel.com>
Message-ID: <b52a2cca-cb5c-d47f-131e-7db297f78958@linux.intel.com>
Date: Mon, 5 Mar 2018 11:40:20 -0800
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On 03/03/2018 12:00 PM, Alexander Popov wrote:
> @@ -128,6 +134,7 @@ static long syscall_trace_enter(struct pt_regs *regs)
>  
>  	do_audit_syscall_entry(regs, arch);
>  
> +	erase_kstack();
>  	return ret ?: regs->orig_ax;
>  }

This seems like an odd place to be clearing the stack.  Why was it done her?