eina: fix a possible race condition during eina_file_close.

The lock on the main hash was taken to late (after we took the decision
to remove the targeted Eina_File from the cache), this means it was possible
to get an Eina_File from the cache that was going to be removed. This patch
attempt to fix that potential race condition.

Hopefully should fix T461.

ChangeLog

@@ -1,3 +1,7 @@
+2013-11-20  Cedric Bail
+
+	* Eina: Fix a possible race condition during eina_file_close.
+
 2013-11-19  Tom Hacohen
 
 	* Evas textblock: Fixed order of tags inserted with markup_app/prepend.

NEWS

@@ -268,7 +268,8 @@ Fixes:
      - Fix memory leak in eina_xattr_value_ls.
      - Fix magic failure in eina_value_array_count when array has not been allocated.
      - Fix issue when wchar_t is signed and eina_unicode does negative array lookups.
-     - Eina: fix eina_file_map_lines() to not drop of one character in the last line.
+     - Fix eina_file_map_lines() to not drop of one character in the last line.
+     - Fix a possible race condition during eina_file_close().
     * Eet:
      - Fix PPC (big endian) image codec bug.
      - Fix leak in eet_pbkdf2_sha1 with OpenSSL.

src/lib/eina/eina_file.c

@@ -305,11 +305,6 @@ eina_file_real_close(Eina_File *file)
 {
    Eina_File_Map *map;
 
-   if (file->refcount != 0) return;
-
-   eina_hash_free(file->rmap);
-   eina_hash_free(file->map);
-
    EINA_LIST_FREE(file->dead_map, map)
      {
         munmap(map->map, map->length);
@@ -320,8 +315,6 @@ eina_file_real_close(Eina_File *file)
      munmap(file->global_map, file->length);
 
    if (file->fd != -1) close(file->fd);
-
-   free(file);
 }
 
 static void
@@ -912,6 +905,8 @@ eina_file_open(const char *path, Eina_Bool shared)
         n->shared = shared;
         eina_lock_new(&n->lock);
         eina_hash_direct_add(_eina_file_cache, n->filename, n);
+
+	EINA_MAGIC_SET(n, EINA_FILE_MAGIC);
      }
    else
      {

src/lib/eina/eina_file_common.c

@@ -451,17 +451,26 @@ eina_file_close(Eina_File *file)
 
    EINA_SAFETY_ON_NULL_RETURN(file);
 
+   eina_lock_take(&_eina_file_lock_cache);
+
    eina_lock_take(&file->lock);
    file->refcount--;
    if (file->refcount == 0) leave = EINA_FALSE;
    eina_lock_release(&file->lock);
-   if (leave) return;
-
-   eina_lock_take(&_eina_file_lock_cache);
+   if (leave) goto end;
 
    eina_hash_del(_eina_file_cache, file->filename, file);
+
+   // Backend specific file resource close
    eina_file_real_close(file);
 
+   // Generic destruction of the file
+   eina_hash_free(file->rmap); file->rmap = NULL;
+   eina_hash_free(file->map); file->map = NULL;
+   EINA_MAGIC_SET(file, 0);
+   free(file);
+
+ end:
    eina_lock_release(&_eina_file_lock_cache);
 }
 

src/lib/eina/eina_file_common.h

@@ -24,11 +24,14 @@
 #include "eina_lock.h"
 #include "eina_list.h"
 
+#define EINA_FILE_MAGIC 0xFEEDBEEF
+
 typedef struct _Eina_File_Map Eina_File_Map;
 typedef struct _Eina_Lines_Iterator Eina_Lines_Iterator;
 
 struct _Eina_File
 {
+   EINA_MAGIC;
    const char *filename;
 
    Eina_Hash *map;

src/lib/eina/eina_file_win32.c

@@ -366,9 +366,6 @@ eina_file_real_close(Eina_File *file)
 {
    Eina_File_Map *map;
 
-   eina_hash_free(file->rmap);
-   eina_hash_free(file->map);
-
    EINA_LIST_FREE(file->dead_map, map)
      {
         UnmapViewOfFile(map->map);
@@ -380,8 +377,6 @@ eina_file_real_close(Eina_File *file)
 
    if (file->fm) CloseHandle(file->fm);
    if (file->handle) CloseHandle(file->handle);
-
-   free(file);
 }
 
 static void
@@ -837,6 +832,8 @@ eina_file_open(const char *path, Eina_Bool shared)
         n->shared = shared;
         eina_lock_new(&n->lock);
         eina_hash_direct_add(_eina_file_cache, n->filename, n);
+
+	EINA_MAGIC_SET(n, EINA_FILE_MAGIC);
      }
    else
      {

src/tests/eina/eina_test_file.c

@@ -441,6 +441,39 @@ START_TEST(eina_test_file_virtualize)
 }
 END_TEST
 
+static void *
+_eina_test_file_thread(void *data EINA_UNUSED, Eina_Thread t EINA_UNUSED)
+{
+   Eina_File *f;
+   unsigned int i;
+
+   for (i = 0; i < 10000; ++i)
+     {
+        f = eina_file_open("/bin/sh", EINA_FALSE);
+        fail_if(!f);
+        eina_file_close(f);
+     }
+
+   return NULL;
+}
+
+START_TEST(eina_test_file_thread)
+{
+   Eina_Thread th[4];
+   unsigned int i;
+
+   fail_if(!eina_init());
+
+   for (i = 0; i < 4; i++)
+     fail_if(!(eina_thread_create(&th[i], EINA_THREAD_NORMAL, 0, _eina_test_file_thread, NULL)));
+
+   for (i = 0; i < 4; i++)
+     fail_if(eina_thread_join(th[i]) != NULL);
+
+   eina_shutdown();
+}
+END_TEST
+
 void
 eina_test_file(TCase *tc)
 {
@@ -449,5 +482,6 @@ eina_test_file(TCase *tc)
    tcase_add_test(tc, eina_file_ls_simple);
    tcase_add_test(tc, eina_file_map_new_test);
    tcase_add_test(tc, eina_test_file_virtualize);
+   tcase_add_test(tc, eina_test_file_thread);
 }