On Fri, Jun 22, 2018 at 3:47 AM Ondrej Mosnacek <omosnace@xxxxxxxxxx> wrote: > št 21. 6. 2018 o 23:17 Paul Moore <paul@xxxxxxxxxxxxxx> napísal(a): > > On Thu, Jun 21, 2018 at 4:33 AM Ondrej Mosnacek <omosnace@xxxxxxxxxx> wrote: > > > The groups-related functions declared in include/linux/cred.h are > > > defined in kernel/groups.c, which is compiled only when > > > CONFIG_MULTIUSER=y. Move all these function declarations under #ifdef > > > CONFIG_MULTIUSER to help avoid accidental usage in contexts where > > > CONFIG_MULTIUSER might be disabled. > > > > > > This patch also adds a fallback for groups_search(). Currently this > > > function is only called from kernel/groups.c itself and > > > keys/permissions.c, which depends on CONFIG_MULTIUSER. However, the > > > audit subsystem (which does not depend on CONFIG_MULTIUSER) calls this > > > function in -next, so the fallback will be needed to avoid compilation > > > errors or ugly workarounds. > > > > > > See also: > > > https://lkml.org/lkml/2018/6/20/670 > > > https://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit.git/commit/?h=next&id=af85d1772e31fed34165a1b3decef340cf4080c0 > > > > > > Reported-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> > > > Signed-off-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx> > > > --- > > > include/linux/cred.h | 16 +++++++++++----- > > > 1 file changed, 11 insertions(+), 5 deletions(-) > > > > > > diff --git a/include/linux/cred.h b/include/linux/cred.h > > > index 631286535d0f..8917768453cc 100644 > > > --- a/include/linux/cred.h > > > +++ b/include/linux/cred.h > > > @@ -65,6 +65,12 @@ extern void groups_free(struct group_info *); > > > > > > extern int in_group_p(kgid_t); > > > extern int in_egroup_p(kgid_t); > > > + > > > +extern int set_current_groups(struct group_info *); > > > +extern void set_groups(struct cred *, struct group_info *); > > > +extern int groups_search(const struct group_info *, kgid_t); > > > +extern bool may_setgroups(void); > > > +extern void groups_sort(struct group_info *); > > > #else > > > static inline void groups_free(struct group_info *group_info) > > > { > > > @@ -78,12 +84,12 @@ static inline int in_egroup_p(kgid_t grp) > > > { > > > return 1; > > > } > > > + > > > +static inline int groups_search(const struct group_info *group_info, kgid_t grp) > > > +{ > > > + return 0; > > > > Is this the right fallback value? If CONFIG_MULTIUSER is disabled, > > wouldn't we always want to indicate a group match? The in_group_p() > > and in_egroup_p() dummy functions would seem to indicate that is the > > correct behavior ... > > Hm, indeed this is a bit tricky and I'm guilty of not noticing this... > > The way I see it (now that I though about it a little), there are > basically two possible semantics of groups_search(): > 1. as an (auxiliary) permissions checking function (like > in_[e]group_p()) -- in this case we would expect the same return value > as in_group_p(), i.e. 1. > 2. as a function that simply checks if a group is contained in a list > of groups (taken from a cred struct) -- in this case we would expect > it to return 0 in single-user mode, since there will be always no > supplemental groups set for any task (if I understand it right). > > I guess no matter which semantic we pick, we might confuse someone > expecting the other one, so I would suggest dropping this patch (or at > least the fallbacks for groups_search) and explicitly handle the > single-user case in audit. > > We should probably default to 1 in audit anyway, because the original > code used in_[e]group_p(). Even though 0 would seem more logical to > me, comparing GIDs doesn't really make sense in single-user mode > anyway, so keeping the legacy behavior will be safer. (In fact now > that I think of it, having audit enabled (or even compiled) in > single-user mode does not make much sense either... maybe we should > just make CONFIG_AUDIT depend on CONFIG_MULTIUSER...). If CONFIG_MULTIUSER is unset then basically everything runs as root:root, there is no user separation anymore. With that in mind it seems the proper behavior is to always return 1 when groups_search() is called. Please make the adjustment and resubmit your patch. -- paul moore www.paul-moore.com -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
