Fix concurrency bugs in FAT_getAttr/FAT_setAttr. (#13)

A relatively rare concurrency bug existed in these methods due to them not
correctly holding the partition lock during calls to
_FAT_directory_entryFromPath. That method can trigger reads to the partition.
Due to the lock not being held, another thread could still trigger a concurrent
read, potentially corrupting the cache. The fix is simply to ensure the lock is
held around the calls.

Author: Chadderz121

source/fatfile.c

@@ -46,6 +46,7 @@
 #include "lock.h"
 
 bool _FAT_findEntry(const char *path, DIR_ENTRY *dirEntry) {
+	bool r;
 	PARTITION *partition = _FAT_partition_getPartitionFromPath(path);
 
 	// Check Partition
@@ -61,8 +62,11 @@ bool _FAT_findEntry(const char *path, DIR_ENTRY *dirEntry) {
 	}
 
 	// Search for the file on the disc
-	return _FAT_directory_entryFromPath (partition, dirEntry, path, NULL);
+	_FAT_lock(&partition->lock);
+	r = _FAT_directory_entryFromPath (partition, dirEntry, path, NULL);
+	_FAT_unlock(&partition->lock);
 
+	return r;
 }
 
 int	FAT_getAttr(const char *file) {
@@ -92,17 +96,18 @@ int FAT_setAttr(const char *file, uint8_t attr) {
 	if (strchr (file, ':') != NULL)
 		return -1;
 
+	// Lock Partition
+	_FAT_lock(&partition->lock);
+
 	// Get DIR_ENTRY
-	if( !_FAT_directory_entryFromPath (partition, &dirEntry, file, NULL) )
+	if( !_FAT_directory_entryFromPath (partition, &dirEntry, file, NULL) ) {
+		_FAT_unlock(&partition->lock); // Unlock Partition
 		return -1;
+	}
 
 	// Get Entry-End
 	entryEnd = dirEntry.dataEnd;
 
-	// Lock Partition
-	_FAT_lock(&partition->lock);
-
-
 	// Write Data
 	_FAT_cache_writePartialSector (
 		partition->cache // Cache to write