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From: "Andrey A. Chernov" <ache@FreeBSD.org>
Date: Mon, 5 Sep 2016 04:49:59 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r305409 - head/lib/libc/stdio
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Author: ache
Date: Mon Sep  5 04:49:58 2016
New Revision: 305409
URL: https://svnweb.freebsd.org/changeset/base/305409

Log:
  1) Prevent out of bounds access to ws[-1] (passed buffer) which happens
  when the first mb sequence is incomplete and there are not enougn chars in
  the read buffer. ws[-1] may lead to memory faults or false results, in
  case the memory here contains '\n'.
  
  2) Fix EOF checking I mess in my previos r305406 commit.
  
  MFC after:      3 days

Modified:
  head/lib/libc/stdio/fgetws.c

Modified: head/lib/libc/stdio/fgetws.c
==============================================================================
--- head/lib/libc/stdio/fgetws.c	Mon Sep  5 04:47:31 2016	(r305408)
+++ head/lib/libc/stdio/fgetws.c	Mon Sep  5 04:49:58 2016	(r305409)
@@ -93,7 +93,7 @@ fgetws_l(wchar_t * __restrict ws, int n,
 		fp->_p = (unsigned char *)src;
 		n -= nconv;
 		wsp += nconv;
-	} while (wsp[-1] != L'\n' && n > 1 && (fp->_r > 0 ||
+	} while ((wsp == ws || wsp[-1] != L'\n') && n > 1 && (fp->_r > 0 ||
 	    (sret = __srefill(fp)) == 0));
 	if (sret && !__sfeof(fp))
 		/* ferror */
@@ -104,7 +104,7 @@ fgetws_l(wchar_t * __restrict ws, int n,
 		errno = EILSEQ;
 		goto error;
 	}
-	if (sret)
+	if (wsp == ws)
 		/* EOF */
 		goto error;
 	*wsp = L'\0';