1 files changed, 19 insertions, 4 deletions

diff --git a/include/linux/capability.h b/include/linux/capability.h
index 4864a43b2b45..c3021105edc0 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -377,7 +377,21 @@ struct cpu_vfs_cap_data {
 #define CAP_FOR_EACH_U32(__capi)  \
         for (__capi = 0; __capi < _KERNEL_CAPABILITY_U32S; ++__capi)
 
+/*
+ * CAP_FS_MASK and CAP_NFSD_MASKS:
+ *
+ * The fs mask is all the privileges that fsuid==0 historically meant.
+ * At one time in the past, that included CAP_MKNOD and CAP_LINUX_IMMUTABLE.
+ *
+ * It has never meant setting security.* and trusted.* xattrs.
+ *
+ * We could also define fsmask as follows:
+ *   1. CAP_FS_MASK is the privilege to bypass all fs-related DAC permissions
+ *   2. The security.* and trusted.* xattrs are fs-related MAC permissions
+ */
+
 # define CAP_FS_MASK_B0     (CAP_TO_MASK(CAP_CHOWN)             \
+                            | CAP_TO_MASK(CAP_MKNOD)            \
                             | CAP_TO_MASK(CAP_DAC_OVERRIDE)     \
                             | CAP_TO_MASK(CAP_DAC_READ_SEARCH)  \
                             | CAP_TO_MASK(CAP_FOWNER)           \
@@ -392,11 +406,12 @@ struct cpu_vfs_cap_data {
 # define CAP_EMPTY_SET    ((kernel_cap_t){{ 0, 0 }})
 # define CAP_FULL_SET     ((kernel_cap_t){{ ~0, ~0 }})
 # define CAP_INIT_EFF_SET ((kernel_cap_t){{ ~CAP_TO_MASK(CAP_SETPCAP), ~0 }})
-# define CAP_FS_SET       ((kernel_cap_t){{ CAP_FS_MASK_B0, CAP_FS_MASK_B1 } })
+# define CAP_FS_SET       ((kernel_cap_t){{ CAP_FS_MASK_B0 \
+                                    | CAP_TO_MASK(CAP_LINUX_IMMUTABLE), \
+                                    CAP_FS_MASK_B1 } })
 # define CAP_NFSD_SET     ((kernel_cap_t){{ CAP_FS_MASK_B0 \
-                                            | CAP_TO_MASK(CAP_SYS_RESOURCE) \
-                                            | CAP_TO_MASK(CAP_MKNOD), \
-                                            CAP_FS_MASK_B1 } })
+                                    | CAP_TO_MASK(CAP_SYS_RESOURCE), \
+                                    CAP_FS_MASK_B1 } })
 
 #endif /* _KERNEL_CAPABILITY_U32S != 2 */