__sinit initialises some common file descriptors as line buffered and relies on the first users of such FDs to call __smakebuf_r. If __smakebuf_r realises there's no space for a buffer (malloc returns NULL), it makes them unbuffered. However, while setting the __SNBF bit, it doesn't clear the __SLBF bit in the flags. Depending on the order in which functions check buffering flags in the FD, sometime they assume it's line buffered (e.g. __sfvwrite_r), trashing application memory that's not really been allocated to them. This patch solves the problem by clearing the unbuffered/line buffered flag when setting the line buffered/unbuffered flag.