groups: Consolidate the setgroups permission checks

Today there are 3 instances of setgroups and due to an oversight their
permission checking has diverged.  Add a common function so that
they may all share the same permission checking code.

This corrects the current oversight in the current permission checks
and adds a helper to avoid this in the future.

A user namespace security fix will update this new helper, shortly.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

diff --git a/arch/s390/kernel/compat_linux.c b/arch/s390/kernel/compat_linux.c
index ca38139..437e611 100644 (file)
--- a/arch/s390/kernel/compat_linux.c
+++ b/arch/s390/kernel/compat_linux.c
@@ -249,7 +249,7 @@ COMPAT_SYSCALL_DEFINE2(s390_setgroups16, int, gidsetsize, u16 __user *, grouplis
        struct group_info *group_info;
        int retval;
 
-       if (!capable(CAP_SETGID))
+       if (!may_setgroups())
                return -EPERM;
        if ((unsigned)gidsetsize > NGROUPS_MAX)
                return -EINVAL;

diff --git a/include/linux/cred.h b/include/linux/cred.h
index b2d0820..2fb2ca2 100644 (file)
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -68,6 +68,7 @@ extern void groups_free(struct group_info *);
 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);
 
 /* access the groups "array" with this macro */
 #define GROUP_AT(gi, i) \

diff --git a/kernel/groups.c b/kernel/groups.c
index 451698f..02d8a25 100644 (file)
--- a/kernel/groups.c
+++ b/kernel/groups.c
@@ -213,6 +213,13 @@ out:
        return i;
 }
 
+bool may_setgroups(void)
+{
+       struct user_namespace *user_ns = current_user_ns();
+
+       return ns_capable(user_ns, CAP_SETGID);
+}
+
 /*
  *     SMP: Our groups are copy-on-write. We can set them safely
  *     without another task interfering.
@@ -223,7 +230,7 @@ SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist)
        struct group_info *group_info;
        int retval;
 
-       if (!ns_capable(current_user_ns(), CAP_SETGID))
+       if (!may_setgroups())
                return -EPERM;
        if ((unsigned)gidsetsize > NGROUPS_MAX)
                return -EINVAL;

diff --git a/kernel/uid16.c b/kernel/uid16.c
index 602e5bb..d58cc4d 100644 (file)
--- a/kernel/uid16.c
+++ b/kernel/uid16.c
@@ -176,7 +176,7 @@ SYSCALL_DEFINE2(setgroups16, int, gidsetsize, old_gid_t __user *, grouplist)
        struct group_info *group_info;
        int retval;
 
-       if (!ns_capable(current_user_ns(), CAP_SETGID))
+       if (!may_setgroups())
                return -EPERM;
        if ((unsigned)gidsetsize > NGROUPS_MAX)
                return -EINVAL;