Attempt to fix the mkdir LSM race.

Doing a world writeable mkdir and _then_ adding a label seems like a race
window, so set the global "create stuff with these labels" context, then
do the creates.

2 files changed, 15 insertions, 8 deletions

diff --git a/lib/lsm.h b/lib/lsm.h
index 660917aa..d7e7de9c 100644
--- a/lib/lsm.h
+++ b/lib/lsm.h
@@ -7,6 +7,7 @@
 #include <selinux/selinux.h>
 #else
 #define is_selinux_enabled() 0
+#define setfscreatecon(...) (-1)
 #define getcon(...) (-1)
 #define getfilecon(...) (-1)
 #define lgetfilecon(...) (-1)
@@ -27,6 +28,7 @@
 #define smack_new_label_from_self(...) (-1)
 #define smack_new_label_from_path(...) (-1)
 #define smack_new_label_from_file(...) (-1)
+#define smack_set_label_for_self(...) (-1)
 #define smack_set_label_for_path(...) (-1)
 #define smack_set_label_for_file(...) (-1)
 #endif
@@ -58,6 +60,14 @@ static inline char *lsm_context(void)
   return ok ? result : strdup("?");
 }
 
+// Set default label to apply to newly created stuff (NULL to clear it)
+static inline int lsm_set_create(char *context)
+{
+  if (CFG_TOYBOX_SMACK) return smack_set_label_for_self(context);
+  else return setfscreatecon(context);
+}
+
+// Label a file, following symlinks
 static inline int lsm_set_context(char *filename, char *context)
 {
   if (CFG_TOYBOX_SMACK)
@@ -65,6 +75,7 @@ static inline int lsm_set_context(char *filename, char *context)
   else return setfilecon(filename, context);
 }
 
+// Label a file, don't follow symlinks
 static inline int lsm_lset_context(char *filename, char *context)
 {
   if (CFG_TOYBOX_SMACK)
@@ -72,6 +83,7 @@ static inline int lsm_lset_context(char *filename, char *context)
   else return lsetfilecon(filename, context);
 }
 
+// Label a file by filehandle
 static inline int lsm_fset_context(int file, char *context)
 {
   if (CFG_TOYBOX_SMACK)
@@ -79,7 +91,6 @@ static inline int lsm_fset_context(int file, char *context)
   else return fsetfilecon(file, context);
 }
 
-
 // returns -1 in case of error or else the length of the context */
 // context can be NULL to get the length only */
 static inline int lsm_get_context(char *filename, char **context)
diff --git a/toys/posix/mkdir.c b/toys/posix/mkdir.c
index 6e95e541..438e38ea 100644
--- a/toys/posix/mkdir.c
+++ b/toys/posix/mkdir.c
@@ -41,19 +41,15 @@ void mkdir_main(void)
   char **s;
   mode_t mode = (0777&~toys.old_umask);
 
+  if (CFG_MKDIR_Z && (toys.optflags&FLAG_Z))
+    if (0>lsm_set_create(TT.arg_context))
+      error_exit("bad -Z '%s'", TT.arg_context);
 
   if (TT.arg_mode) mode = string_to_mode(TT.arg_mode, 0777);
 
   // Note, -p and -v flags line up with mkpathat() flags
-
   for (s=toys.optargs; *s; s++) {
     if (mkpathat(AT_FDCWD, *s, mode, toys.optflags|1))
       perror_msg("'%s'", *s);
-    else if (CFG_MKDIR_Z && (toys.optflags & FLAG_Z)) {
-      if (lsm_set_context(*s, TT.arg_context)) {
-        rmdir(*s);
-        error_msg("'%s': bad -Z '%s'", *s, TT.arg_context);
-      }
-    }
   }
 }