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From: Will Deacon <will.deacon@arm.com>
To: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Kees Cook <keescook@chromium.org>,
	Catalin Marinas <Catalin.Marinas@arm.com>,
	Deepak Saxena <dsaxena@linaro.org>,
	"arndb@arndb.de" <arndb@arndb.de>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linaro-kernel@lists.linaro.org" <linaro-kernel@lists.linaro.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v6 2/6] arm64: ptrace: allow tracer to skip a system call
Date: Fri, 3 Oct 2014 16:23:28 +0100	[thread overview]
Message-ID: <20141003152328.GB32451@arm.com> (raw)
In-Reply-To: <542BE095.3010107@linaro.org>

On Wed, Oct 01, 2014 at 12:08:05PM +0100, AKASHI Takahiro wrote:
> Will,
> 
> When I was looking into syscall_trace_exit() more closely, I found
> another (big) problem.
> There are two system calls, execve() and rt_sigreturn(), which change
> 'syscallno' in pt_regs to -1 in start_thread() and restore_sigframe(),
> respectively.
> 
> Since syscallno is not valid anymore in syscall_trace_exit() for these
> system calls, we cannot create a correct syscall exit record for tracepoint
> in trace_sys_exit() (=> ftrace_syscall_exit()) and for audit in audit_syscall_exit().
> 
> This does not happen on arm because syscall numbers are kept in
> thread_info on arm.
> 
> How can we deal with this issue?

How is this handled on other architectures? x86, for example, seems to zero
orig_ax when restoring the sigcontext, but leaves it alone in start_thread.

What is the impact of this problem? AFAICT, we just miss some exits, right
(as opposed to an OOPs or the like)?

Will

WARNING: multiple messages have this Message-ID (diff)
From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v6 2/6] arm64: ptrace: allow tracer to skip a system call
Date: Fri, 3 Oct 2014 16:23:28 +0100	[thread overview]
Message-ID: <20141003152328.GB32451@arm.com> (raw)
In-Reply-To: <542BE095.3010107@linaro.org>

On Wed, Oct 01, 2014 at 12:08:05PM +0100, AKASHI Takahiro wrote:
> Will,
> 
> When I was looking into syscall_trace_exit() more closely, I found
> another (big) problem.
> There are two system calls, execve() and rt_sigreturn(), which change
> 'syscallno' in pt_regs to -1 in start_thread() and restore_sigframe(),
> respectively.
> 
> Since syscallno is not valid anymore in syscall_trace_exit() for these
> system calls, we cannot create a correct syscall exit record for tracepoint
> in trace_sys_exit() (=> ftrace_syscall_exit()) and for audit in audit_syscall_exit().
> 
> This does not happen on arm because syscall numbers are kept in
> thread_info on arm.
> 
> How can we deal with this issue?

How is this handled on other architectures? x86, for example, seems to zero
orig_ax when restoring the sigcontext, but leaves it alone in start_thread.

What is the impact of this problem? AFAICT, we just miss some exits, right
(as opposed to an OOPs or the like)?

Will

  reply	other threads:[~2014-10-03 15:23 UTC|newest]

Thread overview: 72+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-21  8:56 [PATCH v6 0/6] arm64: add seccomp support AKASHI Takahiro
2014-08-21  8:56 ` AKASHI Takahiro
2014-08-21  8:56 ` [PATCH v6 1/6] arm64: ptrace: add PTRACE_SET_SYSCALL AKASHI Takahiro
2014-08-21  8:56   ` AKASHI Takahiro
2014-08-21 16:47   ` Kees Cook
2014-08-21 16:47     ` Kees Cook
2014-08-22  0:19     ` AKASHI Takahiro
2014-08-22  0:19       ` AKASHI Takahiro
2014-08-26 17:46       ` Will Deacon
2014-08-26 17:46         ` Will Deacon
2014-08-27  5:32         ` AKASHI Takahiro
2014-08-27  5:32           ` AKASHI Takahiro
2014-09-03 18:34           ` Kees Cook
2014-09-03 18:34             ` Kees Cook
2014-08-21  8:56 ` [PATCH v6 2/6] arm64: ptrace: allow tracer to skip a system call AKASHI Takahiro
2014-08-21  8:56   ` AKASHI Takahiro
2014-08-21 17:08   ` Kees Cook
2014-08-21 17:08     ` Kees Cook
2014-08-22  0:35     ` AKASHI Takahiro
2014-08-22  0:35       ` AKASHI Takahiro
2014-08-26 17:51       ` Will Deacon
2014-08-26 17:51         ` Will Deacon
2014-08-27  5:55         ` AKASHI Takahiro
2014-08-27  5:55           ` AKASHI Takahiro
2014-09-01 11:37           ` Will Deacon
2014-09-01 11:37             ` Will Deacon
2014-09-02  7:58             ` AKASHI Takahiro
2014-09-02  7:58               ` AKASHI Takahiro
2014-09-01 11:47           ` Russell King - ARM Linux
2014-09-01 11:47             ` Russell King - ARM Linux
2014-09-02  8:47             ` AKASHI Takahiro
2014-09-02  8:47               ` AKASHI Takahiro
2014-09-02  9:16               ` Russell King - ARM Linux
2014-09-02  9:16                 ` Russell King - ARM Linux
2014-09-02  9:31                 ` Russell King - ARM Linux
2014-09-02  9:31                   ` Russell King - ARM Linux
2014-09-05 10:08                 ` AKASHI Takahiro
2014-09-05 10:08                   ` AKASHI Takahiro
2014-10-01 11:08         ` AKASHI Takahiro
2014-10-01 11:08           ` AKASHI Takahiro
2014-10-03 15:23           ` Will Deacon [this message]
2014-10-03 15:23             ` Will Deacon
2014-10-06  8:04             ` AKASHI Takahiro
2014-10-06  8:04               ` AKASHI Takahiro
2014-08-21  8:56 ` [PATCH v6 3/6] asm-generic: add generic seccomp.h for secure computing mode 1 AKASHI Takahiro
2014-08-21  8:56   ` AKASHI Takahiro
2014-08-21 17:51   ` Kees Cook
2014-08-21 17:51     ` Kees Cook
2014-08-22  0:38     ` AKASHI Takahiro
2014-08-22  0:38       ` AKASHI Takahiro
2014-08-21  8:56 ` [PATCH v6 4/6] arm64: add seccomp syscall for compat task AKASHI Takahiro
2014-08-21  8:56   ` AKASHI Takahiro
2014-08-21 17:52   ` Kees Cook
2014-08-21 17:52     ` Kees Cook
2014-08-22  0:39     ` AKASHI Takahiro
2014-08-22  0:39       ` AKASHI Takahiro
2014-08-26 17:53   ` Will Deacon
2014-08-26 17:53     ` Will Deacon
2014-08-27  5:57     ` AKASHI Takahiro
2014-08-27  5:57       ` AKASHI Takahiro
2014-08-21  8:56 ` [PATCH v6 5/6] arm64: add SIGSYS siginfo " AKASHI Takahiro
2014-08-21  8:56   ` AKASHI Takahiro
2014-08-21 17:54   ` Kees Cook
2014-08-21 17:54     ` Kees Cook
2014-08-22  0:44     ` AKASHI Takahiro
2014-08-22  0:44       ` AKASHI Takahiro
2014-08-26 17:55   ` Will Deacon
2014-08-26 17:55     ` Will Deacon
2014-08-27  5:58     ` AKASHI Takahiro
2014-08-27  5:58       ` AKASHI Takahiro
2014-08-21  8:56 ` [PATCH v6 6/6] arm64: add seccomp support AKASHI Takahiro
2014-08-21  8:56   ` AKASHI Takahiro

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