commit 705a79f82560ff6472cebed86aa5db04cdea3bce
Author: Florian Weimer <fweimer@redhat.com>
Date:   Wed Nov 30 14:59:27 2016 +0100

    libio: Limit buffer size to 8192 bytes [BZ #4099]
    
    This avoids overly large buffers with network file systems which report
    very large block sizes.

Index: b/libio/filedoalloc.c
===================================================================
--- a/libio/filedoalloc.c
+++ b/libio/filedoalloc.c
@@ -121,7 +121,7 @@ _IO_file_doallocate (fp)
 	    fp->_flags |= _IO_LINE_BUF;
 	}
 #if _IO_HAVE_ST_BLKSIZE
-      if (st.st_blksize > 0)
+      if (st.st_blksize > 0 && st.st_blksize < _IO_BUFSIZ)
 	size = st.st_blksize;
 #endif
     }