[PATCH -next v3] cred: conditionally declare groups-related functions

From: Ondrej Mosnacek <omosnace@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Ondrej Mosnacek <omosnace@redhat.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Paul Moore <paul@paul-moore.com>, Eric Paris <eparis@redhat.com>,
	David Howells <dhowells@redhat.com>,
	linux-kernel@vger.kernel.org, linux-next@vger.kernel.org,
	linux-audit@redhat.com
Subject: [PATCH -next v3] cred: conditionally declare groups-related functions
Date: Tue, 26 Jun 2018 13:04:42 +0200	[thread overview]
Message-ID: <20180626110442.21014-1-omosnace@redhat.com> (raw)

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
security/keys/permissions.c, where the call is (by coincidence)
optimized away in case CONFIG_MULTIUSER=n. 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@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
---

Changes:
    v2->v3: commit message corrections
    v1->v2: change default return value of groups_search() to 1

 include/linux/cred.h | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/include/linux/cred.h b/include/linux/cred.h
index 631286535d0f..7eed6101c791 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 groups_search(const struct group_info *, kgid_t);
+
+extern int set_current_groups(struct group_info *);
+extern void set_groups(struct cred *, struct group_info *);
+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 +84,11 @@ 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 1;
+}
 #endif
-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 *);
 
 /*
  * The security context of a task
-- 
2.17.1

