On Wed, Mar 11, 2015 at 10:43:50PM +0100, Mikael Pettersson wrote:
> Jann Horn writes:
> > Or should I throw this patch away and write a patch
> > for the prctl() manpage instead that documents that
> > being able to call sigreturn() implies being able to
> > effectively call sigprocmask(), at least on some
> > architectures like X86?
>
> Well, that is the semantics of sigreturn(). It is essentially
> setcontext() [which includes the actions of sigprocmask()], but
> with restrictions on parameter placement (at least on x86).
>
> You could introduce some setting to restrict that aspect for
> seccomp processes, but you can't change this for normal processes
> without breaking things.
Then I think it's probably better and easier to just document the
existing behavior? If a new setting would have to be introduced
and developers would need to be aware of that, it's probably
easier to just tell everyone to use SIGKILL.
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Mikael Pettersson <mikpelinux@gmail.com>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
While writing some additional seccomp tests, I realized
PTRACE_EVENT_SECCOMP wasn't documented yet. Fixed this, and added
additional notes related to ptrace events SIGTRAP details.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Quoting Daniel's response to my FIXME
> Still hoping to hear from Will Drewy regarding this FIXME in the
> page source:
>
> .\" FIXME What is the significance of the line
> .\" ftest->code = BPF_LDX | BPF_W | BPF_ABS;
> .\" in kernel/seccomp.c::seccomp_check_filter()?
This came in from our rework via commit bd4cf0ed331a ("net: filter:
rework/optimize internal BPF interpreter's instruction set"), and
is kernel-internal only, and unused in classic BPF. It translates
into A = *(u32 *) (ctx + K) and will basically load an offset from
the populated seccomp_data (= ctx) to A. For the man-page itself
it has therefore no relevance, hope that clarifies it.
Reviewed-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Revert a wording change, as suggested by Kees Cook.
Reported-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Rename the arguments to install_filter() to improve readability
a little and to remove a little ambiguity. In particular, rename
'arch' to 't_arch' so that it does not get confused with the
seccomp_data field of the same name.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Jann Horn