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    SubjectRe: [PATCH] userns: Replace netlink uses of cap_raised with capable.
    Quoting Eric W. Biederman (ebiederm@xmission.com):
    >
    > In 2009 Philip Reiser notied that a few users of netlink connector
    > interface needed a capability check and added the idiom
    > cap_raised(nsp->eff_cap, CAP_SYS_ADMIN) to a few of them, on the premise
    > that netlink was asynchronous.
    >
    > In 2011 Patrick McHardy noticed we were being silly because netlink is
    > synchronous and removed eff_cap from the netlink_skb_params and changed
    > the idiom to cap_raised(current_cap(), CAP_SYS_ADMIN).
    >
    > Looking at those spots with a fresh eye we should be calling
    > capable(CAP_SYS_ADMIN). The only reason I can see for not calling
    > capable is that it once appeared we were not in the same task as the
    > caller which would have made calling capable() impossible.

    And (just to make sure) that is now absolutely not the case?

    > In the initial user_namespace the only difference between between
    > cap_raised(current_cap(), CAP_SYS_ADMIN) and capable(CAP_SYS_ADMIN)
    > are a few sanity checks and the fact that capable(CAP_SYS_ADMIN)
    > sets PF_SUPERPRIV if we use the capability.
    >
    > Since we are going to be using root privilege setting PF_SUPERPRIV
    > seems the right thing to do.
    >
    > The motivation for this that patch is that in a child user namespace
    > cap_raised(current_cap(),...) tests your capabilities with respect to
    > that child user namespace not capabilities in the initial user namespace
    > and thus will allow processes that should be unprivielged to use the
    > kernel services that are only protected with
    > cap_raised(current_cap(),..).
    >
    > To fix possible user_namespace issues and to just clean up the code
    > replace cap_raised(current_cap(), CAP_SYS_ADMIN) with
    > capable(CAP_SYS_ADMIN).
    >
    > Cc: Patrick McHardy <kaber@trash.net>
    > Cc: Philipp Reisner <philipp.reisner@linbit.com>
    > Cc: Serge E. Hallyn <serge.hallyn@canonical.com>

    Acked-by: Serge E. Hallyn <serge.hallyn@canonical.com>

    thanks,
    -serge

    > Cc: Andrew Morgan <morgan@kernel.org>
    > Cc: Vasiliy Kulikov <segoon@openwall.com>
    > Cc: David Howells <dhowells@redhat.com>
    > Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
    > ---
    > drivers/block/drbd/drbd_nl.c | 2 +-
    > drivers/md/dm-log-userspace-transfer.c | 2 +-
    > drivers/video/uvesafb.c | 2 +-
    > 3 files changed, 3 insertions(+), 3 deletions(-)
    >
    > diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
    > index abfaaca..946166e 100644
    > --- a/drivers/block/drbd/drbd_nl.c
    > +++ b/drivers/block/drbd/drbd_nl.c
    > @@ -2297,7 +2297,7 @@ static void drbd_connector_callback(struct cn_msg *req, struct netlink_skb_parms
    > return;
    > }
    >
    > - if (!cap_raised(current_cap(), CAP_SYS_ADMIN)) {
    > + if (!capable(CAP_SYS_ADMIN)) {
    > retcode = ERR_PERM;
    > goto fail;
    > }
    > diff --git a/drivers/md/dm-log-userspace-transfer.c b/drivers/md/dm-log-userspace-transfer.c
    > index 1f23e04..08d9a20 100644
    > --- a/drivers/md/dm-log-userspace-transfer.c
    > +++ b/drivers/md/dm-log-userspace-transfer.c
    > @@ -134,7 +134,7 @@ static void cn_ulog_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
    > {
    > struct dm_ulog_request *tfr = (struct dm_ulog_request *)(msg + 1);
    >
    > - if (!cap_raised(current_cap(), CAP_SYS_ADMIN))
    > + if (!capable(CAP_SYS_ADMIN))
    > return;
    >
    > spin_lock(&receiving_list_lock);
    > diff --git a/drivers/video/uvesafb.c b/drivers/video/uvesafb.c
    > index 260cca7..9f7d27a 100644
    > --- a/drivers/video/uvesafb.c
    > +++ b/drivers/video/uvesafb.c
    > @@ -73,7 +73,7 @@ static void uvesafb_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *ns
    > struct uvesafb_task *utask;
    > struct uvesafb_ktask *task;
    >
    > - if (!cap_raised(current_cap(), CAP_SYS_ADMIN))
    > + if (!capable(CAP_SYS_ADMIN))
    > return;
    >
    > if (msg->seq >= UVESAFB_TASKS_MAX)
    > --
    > 1.7.2.5


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