From: Kees Cook <keescook@chromium.org>
To: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
Luis Machado <luis.machado@linaro.org>,
catalin.marinas@arm.com, Keno Fischer <keno@juliacomputing.com>,
kernel-team@android.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 6/7] arm64: ptrace: Use NO_SYSCALL instead of -1 in syscall_trace_enter()
Date: Fri, 10 Jul 2020 09:04:08 -0700 [thread overview]
Message-ID: <202007100902.425E50F4D1@keescook> (raw)
In-Reply-To: <20200710130702.30658-7-will@kernel.org>
On Fri, Jul 10, 2020 at 02:07:01PM +0100, Will Deacon wrote:
> Setting a system call number of -1 is special, as it indicates that the
> current system call should be skipped.
>
> Use NO_SYSCALL instead of -1 when checking for this scenario, which is
> different from the -1 returned due to a seccomp failure.
I can't understand this paragraph. NO_SYSCALL is -1, so how is this
"different"?
arch/arm64/include/asm/ptrace.h:#define NO_SYSCALL (-1)
Do you just mean "stop using a literal '-1'"?
-Kees
>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Keno Fischer <keno@juliacomputing.com>
> Cc: Luis Machado <luis.machado@linaro.org>
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
> arch/arm64/kernel/ptrace.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index 89fbee3991a2..1e02e98e68dd 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -1856,12 +1856,12 @@ int syscall_trace_enter(struct pt_regs *regs)
> if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {
> tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
> if (!in_syscall(regs) || (flags & _TIF_SYSCALL_EMU))
> - return -1;
> + return NO_SYSCALL;
> }
>
> /* Do the secure computing after ptrace; failures should be fast. */
> if (secure_computing() == -1)
> - return -1;
> + return NO_SYSCALL;
>
> if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
> trace_sys_enter(regs, regs->syscallno);
> --
> 2.27.0.383.g050319c2ae-goog
>
--
Kees Cook
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next prev parent reply other threads:[~2020-07-10 16:05 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-10 13:06 [PATCH v3 0/7] arm64: Fix single-step handling and syscall tracing Will Deacon
2020-07-10 13:06 ` [PATCH v3 1/7] arm64: ptrace: Consistently use pseudo-singlestep exceptions Will Deacon
2020-07-16 0:27 ` Sasha Levin
2020-07-10 13:06 ` [PATCH v3 2/7] arm64: ptrace: Override SPSR.SS when single-stepping is enabled Will Deacon
2020-07-16 0:27 ` Sasha Levin
2020-07-10 13:06 ` [PATCH v3 3/7] arm64: compat: Ensure upper 32 bits of x0 are zero on syscall return Will Deacon
2020-07-16 0:27 ` Sasha Levin
2020-07-10 13:06 ` [PATCH v3 4/7] arm64: ptrace: Add a comment describing our syscall entry/exit trap ABI Will Deacon
2020-07-10 13:07 ` [PATCH v3 5/7] arm64: syscall: Expand the comment about ptrace and syscall(-1) Will Deacon
2020-07-10 13:07 ` [PATCH v3 6/7] arm64: ptrace: Use NO_SYSCALL instead of -1 in syscall_trace_enter() Will Deacon
2020-07-10 16:04 ` Kees Cook [this message]
2020-07-10 16:11 ` Will Deacon
2020-07-13 2:32 ` Kees Cook
2020-07-10 13:07 ` [PATCH v3 7/7] arm64: Use test_tsk_thread_flag() for checking TIF_SINGLESTEP Will Deacon
2020-07-14 11:57 ` [PATCH v3 0/7] arm64: Fix single-step handling and syscall tracing Luis Machado
2020-07-15 12:25 ` Luis Machado
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