The log replay code now checks if a super block is valid before the current

one gets overwritten; if the log contains invalid data, it will no longer
render the whole disk unreadable. This should have helped to prevent bug #1911
(but of course the problem that there is invalid data in the log in the first
place remains).


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@24381 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/add-ons/kernel/file_systems/bfs/Journal.cpp

@@ -419,12 +419,22 @@ Journal::_ReplayRunArray(int32 *_start)
 			if (data == NULL)
 				RETURN_ERROR(B_IO_ERROR);
 
-			ssize_t written = write_pos(fVolume->Device(),
-				offset + (i * blockSize), data, blockSize);
+			// TODO: eventually check other well known offsets, like the
+			// root and index dirs
+			if (offset == 0) {
+				// This log entry writes over the super block - check if
+				// it's valid!
+				if (Volume::CheckSuperBlock(data) != B_OK)
+					RETURN_ERROR(B_BAD_DATA);
+			}
+
+			ssize_t written = write_pos(fVolume->Device(), offset, data,
+				blockSize);
 			if (written != blockSize)
 				RETURN_ERROR(B_IO_ERROR);
 
 			blockNumber = (blockNumber + 1) % fLogSize;
+			offset += blockSize;
 			count++;
 		}
 	}

src/add-ons/kernel/file_systems/bfs/Volume.cpp

@@ -558,25 +558,42 @@ Volume::RemoveQuery(Query *query)
 //	#pragma mark - Disk scanning and initialization
 
 
-status_t
+/*static*/ status_t
+Volume::CheckSuperBlock(const uint8* data, uint32* _offset)
+{
+	disk_super_block* superBlock = (disk_super_block*)(data + 512);
+	if (superBlock->IsValid()) {
+		if (_offset != NULL)
+			*_offset = 512;
+		return B_OK;
+	}
+
+#ifndef BFS_LITTLE_ENDIAN_ONLY
+	// For PPC, the super block might be located at offset 0
+	superBlock = (disk_super_block*)data;
+	if (superBlock->IsValid()) {
+		if (_offset != NULL)
+			*_offset = 0;
+		return B_OK;
+	}
+#endif
+
+	return B_BAD_VALUE;
+}
+
+
+/*static*/ status_t
 Volume::Identify(int fd, disk_super_block *superBlock)
 {
-	char buffer[1024];
+	uint8 buffer[1024];
 	if (read_pos(fd, 0, buffer, sizeof(buffer)) != sizeof(buffer))
 		return B_IO_ERROR;
 
-	memcpy(superBlock, buffer + 512, sizeof(disk_super_block));
-	if (!superBlock->IsValid()) {
-#ifndef BFS_LITTLE_ENDIAN_ONLY
-		// For PPC, the super block might be located at offset 0
-		memcpy(superBlock, buffer, sizeof(disk_super_block));
-		if (!superBlock->IsValid())
-			return B_BAD_VALUE;
-#else
+	uint32 offset;
+	if (CheckSuperBlock(buffer, &offset) != B_OK)
 		return B_BAD_VALUE;
-#endif
-	}
 
+	memcpy(superBlock, buffer + offset, sizeof(disk_super_block));
 	return B_OK;
 }
 

src/add-ons/kernel/file_systems/bfs/Volume.h

@@ -102,6 +102,8 @@ class Volume {
 
 		uint32				GetUniqueID();
 
+		static status_t		CheckSuperBlock(const uint8* data,
+								uint32* _offset = NULL);
 		static status_t		Identify(int fd, disk_super_block *superBlock);
 
 	protected: