Linux 3.8 compat: Use kuid_t/kgid_t when required

When CONFIG_UIDGID_STRICT_TYPE_CHECKS is enabled uid_t/git_t are
replaced by kuid_t/kgid_t, which are structures instead of integral
types. This causes any code that uses an integral type to fail to build.
The User Namespace functionality introduced in Linux 3.8 requires
CONFIG_UIDGID_STRICT_TYPE_CHECKS, so we could not build against any
kernel that supported it.

We resolve this by converting between the new kuid_t/kgid_t structures
and the original uid_t/gid_t types.

Original-patch-by: DHE
Rewrite-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #260

config/spl-build.m4

@@ -73,6 +73,7 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [
 	SPL_AC_INODE_TRUNCATE_RANGE
 	SPL_AC_FS_STRUCT_SPINLOCK
 	SPL_AC_CRED_STRUCT
+	SPL_AC_KUIDGID_T
 	SPL_AC_GROUPS_SEARCH
 	SPL_AC_PUT_TASK_STRUCT
 	SPL_AC_5ARGS_PROC_HANDLER
@@ -1866,6 +1867,36 @@ AC_DEFUN([SPL_AC_CRED_STRUCT], [
 	])
 ])
 
+
+dnl #
+dnl # User namespaces, use kuid_t in place of uid_t
+dnl # where available. Not strictly a user namespaces thing
+dnl # but it should prevent surprises
+dnl #
+AC_DEFUN([SPL_AC_KUIDGID_T], [
+	AC_MSG_CHECKING([whether kuid_t/kgid_t is available])
+	SPL_LINUX_TRY_COMPILE([
+		#include <linux/uidgid.h>
+	], [
+		kuid_t userid = KUIDT_INIT(0);
+		kgid_t groupid = KGIDT_INIT(0);
+	],[
+		SPL_LINUX_TRY_COMPILE([
+			#include <linux/uidgid.h>
+		], [
+			kuid_t userid = 0;
+			kgid_t groupid = 0;
+		],[
+			AC_MSG_RESULT(yes; optional)
+		],[
+			AC_MSG_RESULT(yes; mandatory)
+			AC_DEFINE(HAVE_KUIDGID_T, 1, [kuid_t/kgid_t in use])
+		])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])
+
 dnl #
 dnl # Custom SPL patch may export this symbol.
 dnl #
@@ -1873,8 +1904,15 @@ AC_DEFUN([SPL_AC_GROUPS_SEARCH],
 	[AC_MSG_CHECKING([whether groups_search() is available])
 	SPL_LINUX_TRY_COMPILE_SYMBOL([
 		#include <linux/cred.h>
+		#ifdef HAVE_KUIDGID_T
+		#include <linux/uidgid.h>
+		#endif
 	], [
+		#ifdef HAVE_KUIDGID_T
+		groups_search(NULL, KGIDT_INIT(0));
+		#else
 		groups_search(NULL, 0);
+		#endif
 	], [groups_search], [], [
 		AC_MSG_RESULT(yes)
 		AC_DEFINE(HAVE_GROUPS_SEARCH, 1, [groups_search() is available])

include/sys/cred.h

@@ -45,6 +45,36 @@ typedef struct task_struct cred_t;
 
 #endif /* HAVE_CRED_STRUCT */
 
+#ifdef HAVE_KUIDGID_T
+
+ /*
+  * Linux 3.8+ uses typedefs to redefine uid_t and gid_t. We have to rename the
+  * typedefs to recover the original types. We then can use them provided that
+  * we are careful about translating from k{g,u}id_t to the original versions
+  * and vice versa.
+  */
+ #define uid_t xuid_t
+ #define gid_t xgid_t
+ #include <linux/uidgid.h>
+ #undef uid_t
+ #undef gid_t
+
+ #define KUID_TO_SUID(x) (__kuid_val(x))
+ #define KGID_TO_SGID(x) (__kgid_val(x))
+ #define SUID_TO_KUID(x) (KUIDT_INIT(x))
+ #define SGID_TO_KGID(x) (KGIDT_INIT(x))
+ #define KGIDP_TO_SGIDP(x) (&(x)->val)
+
+#else /* HAVE_KUIDGID_T */
+
+ #define KUID_TO_SUID(x) (x)
+ #define KGID_TO_SGID(x) (x)
+ #define SUID_TO_KUID(x) (x)
+ #define SGID_TO_KGID(x) (x)
+ #define KGIDP_TO_SGIDP(x) (x)
+
+#endif /* HAVE_KUIDGID_T */
+
 extern void crhold(cred_t *cr);
 extern void crfree(cred_t *cr);
 extern uid_t crgetuid(const cred_t *cr);

module/spl/spl-cred.c

@@ -38,7 +38,11 @@
 #else
 /* Implementation from 2.6.30 kernel */
 static int
+#ifdef HAVE_KUIDGID_T
+cr_groups_search(const struct group_info *group_info, kgid_t grp)
+#else
 cr_groups_search(const struct group_info *group_info, gid_t grp)
+#endif
 {
 	unsigned int left, right;
 
@@ -49,7 +53,7 @@ cr_groups_search(const struct group_info *group_info, gid_t grp)
 	right = group_info->ngroups;
 	while (left < right) {
 		unsigned int mid = (left+right)/2;
-		int cmp = grp - GROUP_AT(group_info, mid);
+		int cmp = KGID_TO_SGID(grp) - KGID_TO_SGID(GROUP_AT(group_info, mid));
 		if (cmp > 0)
 			left = mid + 1;
 		else if (cmp < 0)
@@ -110,7 +114,7 @@ crgetgroups(const cred_t *cr)
 	gid_t *gids;
 
 	gi = get_group_info(cr->group_info);
-	gids = gi->blocks[0];
+	gids = KGIDP_TO_SGIDP(gi->blocks[0]);
 	put_group_info(gi);
 
 	return gids;
@@ -124,7 +128,7 @@ groupmember(gid_t gid, const cred_t *cr)
 	int rc;
 
 	gi = get_group_info(cr->group_info);
-	rc = cr_groups_search(cr->group_info, gid);
+	rc = cr_groups_search(cr->group_info, SGID_TO_KGID(gid));
 	put_group_info(gi);
 
 	return rc;
@@ -180,7 +184,7 @@ crgetgroups(const cred_t *cr)
 		task_lock((struct task_struct *)cr);
 
 	get_group_info(cr->group_info);
-	gids = cr->group_info->blocks[0];
+	gids = KGID_TO_SGID(cr->group_info->blocks[0]);
 	put_group_info(cr->group_info);
 
 	if (lock)
@@ -215,56 +219,56 @@ groupmember(gid_t gid, const cred_t *cr)
 uid_t
 crgetuid(const cred_t *cr)
 {
-	return cr->euid;
+	return KUID_TO_SUID(cr->euid);
 }
 
 /* Return the real user id */
 uid_t
 crgetruid(const cred_t *cr)
 {
-	return cr->uid;
+	return KUID_TO_SUID(cr->uid);
 }
 
 /* Return the saved user id */
 uid_t
 crgetsuid(const cred_t *cr)
 {
-	return cr->suid;
+	return KUID_TO_SUID(cr->suid);
 }
 
 /* Return the filesystem user id */
 uid_t
 crgetfsuid(const cred_t *cr)
 {
-	return cr->fsuid;
+	return KUID_TO_SUID(cr->fsuid);
 }
 
 /* Return the effective group id */
 gid_t
 crgetgid(const cred_t *cr)
 {
-	return cr->egid;
+	return KGID_TO_SGID(cr->egid);
 }
 
 /* Return the real group id */
 gid_t
 crgetrgid(const cred_t *cr)
 {
-	return cr->gid;
+	return KGID_TO_SGID(cr->gid);
 }
 
 /* Return the saved group id */
 gid_t
 crgetsgid(const cred_t *cr)
 {
-	return cr->sgid;
+	return KGID_TO_SGID(cr->sgid);
 }
 
 /* Return the filesystem group id */
 gid_t
 crgetfsgid(const cred_t *cr)
 {
-	return cr->fsgid;
+	return KGID_TO_SGID(cr->fsgid);
 }
 
 EXPORT_SYMBOL(crhold);

module/spl/spl-vnode.c

@@ -24,6 +24,7 @@
  *  Solaris Porting Layer (SPL) Vnode Implementation.
 \*****************************************************************************/
 
+#include <sys/cred.h>
 #include <sys/vnode.h>
 #include <linux/falloc.h>
 #include <spl-debug.h>
@@ -616,8 +617,8 @@ vn_getattr(vnode_t *vp, vattr_t *vap, int flags, void *x3, void *x4)
 
 	vap->va_type          = vn_mode_to_vtype(stat.mode);
 	vap->va_mode          = stat.mode;
-	vap->va_uid           = stat.uid;
+	vap->va_uid           = KUID_TO_SUID(stat.uid);
-	vap->va_gid           = stat.gid;
+	vap->va_gid           = KGID_TO_SGID(stat.gid);
 	vap->va_fsid          = 0;
 	vap->va_nodeid        = stat.ino;
 	vap->va_nlink         = stat.nlink;