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Date: Thu, 17 Jul 2014 15:29:57 -0700 From: Kees Cook <keescook@...omium.org> To: Markos Chandras <markos.chandras@...tec.com> Cc: James Hogan <james.hogan@...tec.com>, Paul Burton <paul.burton@...tec.com>, Linux MIPS Mailing List <linux-mips@...ux-mips.org>, Ralf Baechle <ralf@...ux-mips.org>, LKML <linux-kernel@...r.kernel.org> Subject: MIPS seccomp and changing syscalls Hi, I recently fixed a bug in seccomp on ARM that I think may be present in the MIPS implementation too. In arch/mips/kernel/ptrace.c syscall_trace_enter, the syscall variable is used (and returned), but the syscall may be changed by either secure_computing or tracehook_report_syscall_entry (via ptracers which can block and change the registers). (I would note that "ret" is also set but never used, so tracehook_report_syscall_entry failures actually won't get noticed.) The discussion about this bug on ARM is here: https://lkml.org/lkml/2014/6/20/439 I don't yet have a working MIPS environment to test this on, but it feels like the same bug. (Though, for testing, what's the right way to change syscall during PTRACE_SYSCALL? On x86 it's the orig_ax register, on ARM it's a arch-specific ptrace function (PTRACE_SET_SYSCALL). Thanks! -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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