1 files changed, 89 insertions, 7 deletions

diff --git a/fs/xattr_acl.c b/fs/xattr_acl.c
index 69d06b07b169..11efd830b5f5 100644
--- a/fs/xattr_acl.c
+++ b/fs/xattr_acl.c
@@ -9,13 +9,72 @@
 #include <linux/fs.h>
 #include <linux/posix_acl_xattr.h>
 #include <linux/gfp.h>
+#include <linux/user_namespace.h>
 
+/*
+ * Fix up the uids and gids in posix acl extended attributes in place.
+ */
+static void posix_acl_fix_xattr_userns(
+        struct user_namespace *to, struct user_namespace *from,
+        void *value, size_t size)
+{
+        posix_acl_xattr_header *header = (posix_acl_xattr_header *)value;
+        posix_acl_xattr_entry *entry = (posix_acl_xattr_entry *)(header+1), *end;
+        int count;
+        kuid_t uid;
+        kgid_t gid;
+
+        if (!value)
+                return;
+        if (size < sizeof(posix_acl_xattr_header))
+                return;
+        if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
+                return;
+
+        count = posix_acl_xattr_count(size);
+        if (count < 0)
+                return;
+        if (count == 0)
+                return;
+
+        for (end = entry + count; entry != end; entry++) {
+                switch(le16_to_cpu(entry->e_tag)) {
+                case ACL_USER:
+                        uid = make_kuid(from, le32_to_cpu(entry->e_id));
+                        entry->e_id = cpu_to_le32(from_kuid(to, uid));
+                        break;
+                case ACL_GROUP:
+                        gid = make_kgid(from, le32_to_cpu(entry->e_id));
+                        entry->e_id = cpu_to_le32(from_kuid(to, uid));
+                        break;
+                default:
+                        break;
+                }
+        }
+}
+
+void posix_acl_fix_xattr_from_user(void *value, size_t size)
+{
+        struct user_namespace *user_ns = current_user_ns();
+        if (user_ns == &init_user_ns)
+                return;
+        posix_acl_fix_xattr_userns(&init_user_ns, user_ns, value, size);
+}
+
+void posix_acl_fix_xattr_to_user(void *value, size_t size)
+{
+        struct user_namespace *user_ns = current_user_ns();
+        if (user_ns == &init_user_ns)
+                return;
+        posix_acl_fix_xattr_userns(user_ns, &init_user_ns, value, size);
+}
 
 /*
  * Convert from extended attribute to in-memory representation.
  */
 struct posix_acl *
-posix_acl_from_xattr(const void *value, size_t size)
+posix_acl_from_xattr(struct user_namespace *user_ns,
+                     const void *value, size_t size)
 {
         posix_acl_xattr_header *header = (posix_acl_xattr_header *)value;
         posix_acl_xattr_entry *entry = (posix_acl_xattr_entry *)(header+1), *end;
@@ -50,12 +109,21 @@ posix_acl_from_xattr(const void *value, size_t size)
                         case ACL_GROUP_OBJ:
                         case ACL_MASK:
                         case ACL_OTHER:
-                                acl_e->e_id = ACL_UNDEFINED_ID;
                                 break;
 
                         case ACL_USER:
+                                acl_e->e_uid =
+                                        make_kuid(user_ns,
+                                                  le32_to_cpu(entry->e_id));
+                                if (!uid_valid(acl_e->e_uid))
+                                        goto fail;
+                                break;
                         case ACL_GROUP:
-                                acl_e->e_id = le32_to_cpu(entry->e_id);
+                                acl_e->e_gid =
+                                        make_kgid(user_ns,
+                                                  le32_to_cpu(entry->e_id));
+                                if (!gid_valid(acl_e->e_gid))
+                                        goto fail;
                                 break;
 
                         default:
@@ -74,7 +142,8 @@ EXPORT_SYMBOL (posix_acl_from_xattr);
  * Convert from in-memory to extended attribute representation.
  */
 int
-posix_acl_to_xattr(const struct posix_acl *acl, void *buffer, size_t size)
+posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
+                   void *buffer, size_t size)
 {
         posix_acl_xattr_header *ext_acl = (posix_acl_xattr_header *)buffer;
         posix_acl_xattr_entry *ext_entry = ext_acl->a_entries;
@@ -89,9 +158,22 @@ posix_acl_to_xattr(const struct posix_acl *acl, void *buffer, size_t size)
         ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
 
         for (n=0; n < acl->a_count; n++, ext_entry++) {
-                ext_entry->e_tag  = cpu_to_le16(acl->a_entries[n].e_tag);
-                ext_entry->e_perm = cpu_to_le16(acl->a_entries[n].e_perm);
-                ext_entry->e_id   = cpu_to_le32(acl->a_entries[n].e_id);
+                const struct posix_acl_entry *acl_e = &acl->a_entries[n];
+                ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
+                ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
+                switch(acl_e->e_tag) {
+                case ACL_USER:
+                        ext_entry->e_id =
+                                cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
+                        break;
+                case ACL_GROUP:
+                        ext_entry->e_id =
+                                cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
+                        break;
+                default:
+                        ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
+                        break;
+                }
         }
         return real_size;
 }