linux-kernel - Re: [PATCH 5/6] x86/ptrace: down with test_thread_flag(TIF

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 6 Jun 2016 23:19:18 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Dmitry Safonov <dsafonov@...tuozzo.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...hat.com,
	luto@...capital.net, tglx@...utronix.de, hpa@...or.com,
	x86@...nel.org, 0x7f454c46@...il.com, gorcunov@...nvz.org,
	xemul@...tuozzo.com, khorenko@...tuozzo.com,
	Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH 5/6] x86/ptrace: down with test_thread_flag(TIF_IA32)

On 06/01, Dmitry Safonov wrote:
>
> Note, that this will work only if application has changed it's CS.

So, suppose it changes it's CS and crashes,

> If the application does 32-bit syscall with __USER_CS, ptrace
> @@ -1355,7 +1355,7 @@ void update_regset_xstate_info(unsigned int size, u64 xstate_mask)
>  const struct user_regset_view *task_user_regset_view(struct task_struct *task)
>  {
>  #ifdef CONFIG_IA32_EMULATION
> -	if (test_tsk_thread_flag(task, TIF_IA32))
> +	if (!user_64bit_mode(task_pt_regs(task)))
>  #endif

then coredump will do fill_elf_header(view->e_machine) and use EM_X86_64
instead of EM_386, or vice versa...

I simply can't understand is this better or worse, I guess gdb or any
other tool which looks at this coredump will be confused anyway.

Oleg.