linux-kernel - Re: [PATCH 3/8] x86/asm/entry: Zero EXTRA_REGS for stub32

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Date:	Tue, 7 Apr 2015 22:39:59 -0400
From:	Brian Gerst <brgerst@...il.com>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>,
	Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/8] x86/asm/entry: Zero EXTRA_REGS for stub32_execve[at] too

On Tue, Apr 7, 2015 at 4:43 PM, Denys Vlasenko <dvlasenk@...hat.com> wrote:
> The change which affected how execve clears EXTRA_REGS missed
> 32-bit execve syscalls.
>
> Fix this by using 64-bit execve stub epilogue for them too.
>
> Run-tested.
>
> Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
> CC: Linus Torvalds <torvalds@...ux-foundation.org>
> CC: Steven Rostedt <rostedt@...dmis.org>
> CC: Ingo Molnar <mingo@...nel.org>
> CC: Borislav Petkov <bp@...en8.de>
> CC: "H. Peter Anvin" <hpa@...or.com>
> CC: Andy Lutomirski <luto@...capital.net>
> CC: Oleg Nesterov <oleg@...hat.com>
> CC: Frederic Weisbecker <fweisbec@...il.com>
> CC: Alexei Starovoitov <ast@...mgrid.com>
> CC: Will Drewry <wad@...omium.org>
> CC: Kees Cook <keescook@...omium.org>
> CC: x86@...nel.org
> CC: linux-kernel@...r.kernel.org
> ---
>  arch/x86/ia32/ia32entry.S  |  2 --
>  arch/x86/kernel/entry_64.S | 15 +++++++++++++++
>  2 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
> index 5d8f987..a821b1c 100644
> --- a/arch/x86/ia32/ia32entry.S
> +++ b/arch/x86/ia32/ia32entry.S
> @@ -571,8 +571,6 @@ GLOBAL(\label)
>
>         PTREGSCALL stub32_rt_sigreturn, sys32_rt_sigreturn
>         PTREGSCALL stub32_sigreturn, sys32_sigreturn
> -       PTREGSCALL stub32_execve, compat_sys_execve
> -       PTREGSCALL stub32_execveat, compat_sys_execveat
>         PTREGSCALL stub32_fork, sys_fork
>         PTREGSCALL stub32_vfork, sys_vfork
>
> diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
> index 1b0793c..8e3ba38 100644
> --- a/arch/x86/kernel/entry_64.S
> +++ b/arch/x86/kernel/entry_64.S
> @@ -461,6 +461,21 @@ ENTRY(stub_x32_execveat)
>  END(stub_x32_execveat)
>  #endif
>
> +#ifdef CONFIG_IA32_EMULATION
> +ENTRY(stub32_execve)
> +       CFI_STARTPROC
> +       call    compat_sys_execve
> +       jmp     return_from_execve
> +       CFI_ENDPROC
> +END(stub32_execve)
> +ENTRY(stub32_execveat)
> +       CFI_STARTPROC
> +       call    compat_sys_execveat
> +       jmp     return_from_execve
> +       CFI_ENDPROC
> +END(stub32_execveat)
> +#endif
> +
>  /*
>   * sigreturn is special because it needs to restore all registers on return.
>   * This cannot be done with SYSRET, so use the IRET return path instead.

The X32 and IA32 stubs are now identical and should be merged.

--
Brian Gerst
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