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: [email protected] Signed-off-by: "Eric W. Biederman" <[email protected]>
dzndl · Dec 5, 2014 · 7ff4d90 · 7ff4d90
1 parent 4fed655
commit 7ff4d90
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Showing 4 changed files with 11 additions and 3 deletions.
diff --git 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
@@ -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
@@ -213,6 +213,13 @@ SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist)
 	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
@@ -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;