Messages in this thread | | | From | Andrew Lutomirski <> | Date | Thu, 12 Jan 2012 09:02:49 -0800 | Subject | Re: [RFC,PATCH 1/2] seccomp_filters: system call filtering using BPF |
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On Wed, Jan 11, 2012 at 9:25 AM, Will Drewry <wad@chromium.org> wrote: > This patch adds support for seccomp mode 2. This mode enables dynamic > enforcement of system call filtering policy in the kernel as specified > by a userland task. The policy is expressed in terms of a BPF program, > as is used for userland-exposed socket filtering. Instead of network > data, the BPF program is evaluated over struct user_regs_struct at the > time of the system call (as retrieved using regviews). >
There's some seccomp-related code in the vsyscall emulation path in arch/x86/kernel/vsyscall_64.c. How should time(), getcpu(), and gettimeofday() be handled? If you want filtering to work, there aren't any real syscall registers to inspect, but they could be synthesized.
Preventing a malicious task from figuring out approximately what time it is is basically impossible because of the way that vvars work. I don't know how to change that efficiently.
--Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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