Michael/Andrea,
Would you also like to review the corresponding test cases for the same in
LTP (http://ltp.cvs.sourceforge.net/ltp/ltp/testcases/kernel/syscalls/prctl/),
against the changes in 2.6.23. The testcases are pretty old and may require
review now.
Regards--
Subrata
On Mon, Jun 16, 2008 at 5:45 PM, Michael Kerrisk <
[EMAIL PROTECTED]> wrote:
> Andrea,
>
> Below is my attempt to document the SECCOMP prctl() operations that you
> added
> in 2.6.23. Could you please read, and let me know if I have the details
> correct. Especially take a look at the description of PR_GET_SECCOMP,
> whose
> operation tends to suggest a thinko:
>
> PR_SET_SECCOMP (since Linux 2.6.23)
> Set the secure computing mode for the calling thread. In
> the current implementation, arg2 must be 1. After the
> secure computing mode has been set to 1, the only system
> calls that the thread is permitted to make are read(2),
> write(2), _exit(2), and sigreturn(2). Other system calls
> result in the delivery of a SIGKILL signal. Secure comput-
> ing mode is useful for number-crunching applications that
> may need to execute untrusted byte code, perhaps obtained
> by reading from a pipe or socket. This operation is only
> available if the kernel is configured with CONFIG_SECCOMP
> enabled.
>
> PR_GET_SECCOMP (since Linux 2.6.23)
> Return the secure computing mode of the calling thread.
> Not very useful: if the caller is not in secure computing
> mode, this operation returns 0; if the caller is in secure
> computing mode, then the prctl() call will cause a SIGKILL
> signal to be sent to the process. This operation is only
> available if the kernel is configured with CONFIG_SECCOMP
> enabled.
>
> Have I misunderstood something? Surely it is not really intended that
> PR_GET_SECCOMP be this useless? The alternatives that I can think of would
> be
> that
>
> a) at least the call prctl(PR_GET_SECCOMP) would be among the set of
> permitted
> syscalls in secure computing mode, or
>
> b) there shouldn't be a prctl(PR_GET_SECCOMP) at all.
>
> Cheers,
>
> Michael
>
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--
Regards & Thanks--
Subrata
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