Messages in this thread | | | Subject | Re: [PATCH 5/7] seccomp_filter: Document what seccomp_filter is and how it works. | From | Steven Rostedt <> | Date | Wed, 04 May 2011 12:06:09 -0400 |
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On Wed, 2011-05-04 at 11:54 -0400, Eric Paris wrote:
> As this is a deny by default interface which only allows you to further > restrict you couldn't add more than 1 syscall if you didn't have an > explict 'apply' action. > > SECCOMP_FILTER_SET, __NR_fo, "a=0" > SECCOMP_FILTER_SET, __NR_read, "1" == EPERM > > Maybe apply on set is fine after the first apply, but we definitely need > some way to do more than 1 set before the rules are applied....
So we could have SET be 'or' and APPLY be 'and'.
SECCOMP_FILTER_SET, __NR_foo, "a=0" SECCOMP_FILTER_SET, __NR_read, "1" == EPERM SECCOPM_FILTER_APPLY
SECCOMP_FILTER_SET, __NR_foo, "b=0" SECCOPM_FILTER_APPLY
Will end up being:
(foo: a == 0 || read: "1" == EPERM) && (foo: b == 0)
The second set/apply now removes the read option, and foo only works if a is 0 and b is 0.
This would also work for children, as they can only restrict (with 'and') and can not add more control.
-- Steve
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