2016-12-15 Giuseppe Musumeci <giuseppe.musumeci@broadcom.com>

__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.

1 files changed, 2 insertions, 2 deletions

diff --git a/newlib/libc/stdio/makebuf.c b/newlib/libc/stdio/makebuf.c
index c592578..ab20a08 100644
--- a/newlib/libc/stdio/makebuf.c
+++ b/newlib/libc/stdio/makebuf.c
@@ -55,7 +55,7 @@ _DEFUN(__smakebuf_r, (ptr, fp),
     {
       if (!(fp->_flags & __SSTR))
 	{
-	  fp->_flags |= __SNBF;
+	  fp->_flags = (fp->_flags & ~__SLBF) | __SNBF;
 	  fp->_bf._base = fp->_p = fp->_nbuf;
 	  fp->_bf._size = 1;
 	}
@@ -67,7 +67,7 @@ _DEFUN(__smakebuf_r, (ptr, fp),
       fp->_bf._base = fp->_p = (unsigned char *) p;
       fp->_bf._size = size;
       if (couldbetty && _isatty_r (ptr, fp->_file))
-	fp->_flags |= __SLBF;
+	fp->_flags = (fp->_flags & ~__SNBF) | __SLBF;
       fp->_flags |= flags;
     }
 }