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    SubjectRe: [PATCH v10 1/4] seccomp: hoist struct seccomp_data recalculation higher
    On Sun, Dec 9, 2018 at 10:24 AM Tycho Andersen <tycho@tycho.ws> wrote:
    >
    > In the next patch, we're going to use the sd pointer passed to
    > __seccomp_filter() as the data to pass to userspace. Except that in some
    > cases (__seccomp_filter(SECCOMP_RET_TRACE), emulate_vsyscall(), every time
    > seccomp is inovked on power, etc.) the sd pointer will be NULL in order to
    > force seccomp to recompute the register data. Previously this recomputation
    > happened one level lower, in seccomp_run_filters(); this patch just moves
    > it up a level higher to __seccomp_filter().
    >
    > Thanks Oleg for spotting this.
    >
    > Signed-off-by: Tycho Andersen <tycho@tycho.ws>

    This is fine. :) Applied for -next.

    -Kees

    > CC: Kees Cook <keescook@chromium.org>
    > CC: Andy Lutomirski <luto@amacapital.net>
    > CC: Oleg Nesterov <oleg@redhat.com>
    > CC: Eric W. Biederman <ebiederm@xmission.com>
    > CC: "Serge E. Hallyn" <serge@hallyn.com>
    > Acked-by: Serge Hallyn <serge@hallyn.com>
    > CC: Christian Brauner <christian@brauner.io>
    > CC: Tyler Hicks <tyhicks@canonical.com>
    > CC: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>
    > ---
    > kernel/seccomp.c | 12 ++++++------
    > 1 file changed, 6 insertions(+), 6 deletions(-)
    >
    > diff --git a/kernel/seccomp.c b/kernel/seccomp.c
    > index f2ae2324c232..96afc32e041d 100644
    > --- a/kernel/seccomp.c
    > +++ b/kernel/seccomp.c
    > @@ -188,7 +188,6 @@ static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
    > static u32 seccomp_run_filters(const struct seccomp_data *sd,
    > struct seccomp_filter **match)
    > {
    > - struct seccomp_data sd_local;
    > u32 ret = SECCOMP_RET_ALLOW;
    > /* Make sure cross-thread synced filter points somewhere sane. */
    > struct seccomp_filter *f =
    > @@ -198,11 +197,6 @@ static u32 seccomp_run_filters(const struct seccomp_data *sd,
    > if (WARN_ON(f == NULL))
    > return SECCOMP_RET_KILL_PROCESS;
    >
    > - if (!sd) {
    > - populate_seccomp_data(&sd_local);
    > - sd = &sd_local;
    > - }
    > -
    > /*
    > * All filters in the list are evaluated and the lowest BPF return
    > * value always takes priority (ignoring the DATA).
    > @@ -658,6 +652,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
    > u32 filter_ret, action;
    > struct seccomp_filter *match = NULL;
    > int data;
    > + struct seccomp_data sd_local;
    >
    > /*
    > * Make sure that any changes to mode from another thread have
    > @@ -665,6 +660,11 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
    > */
    > rmb();
    >
    > + if (!sd) {
    > + populate_seccomp_data(&sd_local);
    > + sd = &sd_local;
    > + }
    > +
    > filter_ret = seccomp_run_filters(sd, &match);
    > data = filter_ret & SECCOMP_RET_DATA;
    > action = filter_ret & SECCOMP_RET_ACTION_FULL;
    > --
    > 2.19.1
    >


    --
    Kees Cook

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