From: luto@amacapital.net (Andy Lutomirski)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v5 1/3] arm64: ptrace: reload a syscall number after ptrace operations
Date: Wed, 23 Jul 2014 20:54:00 -0700 [thread overview]
Message-ID: <53D08358.4020902@amacapital.net> (raw)
In-Reply-To: <1406020499-5537-2-git-send-email-takahiro.akashi@linaro.org>
On 07/22/2014 02:14 AM, AKASHI Takahiro wrote:
> Arm64 holds a syscall number in w8(x8) register. Ptrace tracer may change
> its value either to:
> * any valid syscall number to alter a system call, or
> * -1 to skip a system call
>
> This patch implements this behavior by reloading that value into syscallno
> in struct pt_regs after tracehook_report_syscall_entry() or
> secure_computing(). In case of '-1', a return value of system call can also
> be changed by the tracer setting the value to x0 register, and so
> sys_ni_nosyscall() should not be called.
>
> See also:
> 42309ab4, ARM: 8087/1: ptrace: reload syscall number after
> secure_computing() check
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> ---
> arch/arm64/kernel/entry.S | 2 ++
> arch/arm64/kernel/ptrace.c | 13 +++++++++++++
> 2 files changed, 15 insertions(+)
>
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index 5141e79..de8bdbc 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -628,6 +628,8 @@ ENDPROC(el0_svc)
> __sys_trace:
> mov x0, sp
> bl syscall_trace_enter
> + cmp w0, #-1 // skip syscall?
> + b.eq ret_to_user
Does this mean that skipped syscalls will cause exit tracing to be
skipped? If so, then you risk (at least) introducing a nice
user-triggerable OOPS if audit is enabled. This bug existed for *years*
on x86_32, and it amazes me that no one ever triggered it by accident.
(Grr, audit.)
--Andy
next prev parent reply other threads:[~2014-07-24 3:54 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-22 9:14 [PATCH v5 0/3] arm64: Add seccomp support AKASHI Takahiro
2014-07-22 9:14 ` [PATCH v5 1/3] arm64: ptrace: reload a syscall number after ptrace operations AKASHI Takahiro
2014-07-22 20:15 ` Kees Cook
2014-07-23 7:03 ` AKASHI Takahiro
2014-07-23 8:25 ` Will Deacon
2014-07-23 9:09 ` AKASHI Takahiro
2014-07-23 15:13 ` Kees Cook
2014-07-24 3:54 ` Andy Lutomirski [this message]
2014-07-24 5:57 ` AKASHI Takahiro
2014-07-24 15:01 ` Andy Lutomirski
2014-07-25 10:36 ` AKASHI Takahiro
2014-07-25 11:03 ` Will Deacon
2014-07-29 6:49 ` AKASHI Takahiro
2014-07-29 13:26 ` Will Deacon
2014-07-22 9:14 ` [PATCH v5 2/3] asm-generic: Add generic seccomp.h for secure computing mode 1 AKASHI Takahiro
2014-07-24 3:40 ` Andy Lutomirski
2014-07-24 4:41 ` Kees Cook
2014-07-24 5:17 ` AKASHI Takahiro
2014-07-24 14:57 ` Andy Lutomirski
2014-07-25 8:52 ` AKASHI Takahiro
2014-07-22 9:14 ` [PATCH v5 3/3] arm64: Add seccomp support AKASHI Takahiro
2014-07-24 3:52 ` Andy Lutomirski
2014-07-24 5:40 ` AKASHI Takahiro
2014-07-24 15:00 ` Andy Lutomirski
2014-07-24 15:16 ` Catalin Marinas
2014-07-25 9:37 ` AKASHI Takahiro
2014-08-05 15:08 ` Kees Cook
2014-08-08 7:35 ` AKASHI Takahiro
2014-08-11 9:24 ` Will Deacon
2014-08-12 6:57 ` AKASHI Takahiro
2014-08-12 9:40 ` Will Deacon
2014-08-12 11:17 ` AKASHI Takahiro
2014-08-15 14:33 ` Will Deacon
2014-07-22 20:16 ` [PATCH v5 0/3] " Kees Cook
2014-07-23 7:09 ` AKASHI Takahiro
2014-07-23 15:36 ` Kees Cook
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