x86-64 strnlen/wcsnlen: Properly handle the length parameter [BZ# 24097]

On x32, the size_t parameter may be passed in the lower 32 bits of a
64-bit register with the non-zero upper 32 bits.  The string/memory
functions written in assembly can only use the lower 32 bits of a
64-bit register as length or must clear the upper 32 bits before using
the full 64-bit register for length.

This pach fixes strnlen/wcsnlen for x32.  Tested on x86-64 and x32.  On
x86-64, libc.so is the same with and withou the fix.

	[BZ# 24097]
	CVE-2019-6488
	* sysdeps/x86_64/multiarch/strlen-avx2.S: Use RSI_LP for length.
	Clear the upper 32 bits of RSI register.
	* sysdeps/x86_64/strlen.S: Use RSI_LP for length.
	* sysdeps/x86_64/x32/Makefile (tests): Add tst-size_t-strnlen
	and tst-size_t-wcsnlen.
	* sysdeps/x86_64/x32/tst-size_t-strnlen.c: New file.
	* sysdeps/x86_64/x32/tst-size_t-wcsnlen.c: Likewise.

5 files changed, 106 insertions, 11 deletions

diff --git a/sysdeps/x86_64/multiarch/strlen-avx2.S b/sysdeps/x86_64/multiarch/strlen-avx2.S
index aa0ade503f..3e7f14a846 100644
--- a/sysdeps/x86_64/multiarch/strlen-avx2.S
+++ b/sysdeps/x86_64/multiarch/strlen-avx2.S
@@ -42,12 +42,15 @@
 ENTRY (STRLEN)
 # ifdef USE_AS_STRNLEN
 	/* Check for zero length.  */
-	testq	%rsi, %rsi
+	test	%RSI_LP, %RSI_LP
 	jz	L(zero)
 #  ifdef USE_AS_WCSLEN
-	shl	$2, %rsi
+	shl	$2, %RSI_LP
+#  elif defined __ILP32__
+	/* Clear the upper 32 bits.  */
+	movl	%esi, %esi
 #  endif
-	movq	%rsi, %r8
+	mov	%RSI_LP, %R8_LP
 # endif
 	movl	%edi, %ecx
 	movq	%rdi, %rdx
diff --git a/sysdeps/x86_64/strlen.S b/sysdeps/x86_64/strlen.S
index d6fdc3580f..9ab357fc1a 100644
--- a/sysdeps/x86_64/strlen.S
+++ b/sysdeps/x86_64/strlen.S
@@ -59,21 +59,21 @@ ENTRY(strlen)
 
 #ifdef AS_STRNLEN
 /* Do not read anything when n==0.  */
-	test	%rsi, %rsi
+	test	%RSI_LP, %RSI_LP
 	jne	L(n_nonzero)
 	xor	%rax, %rax
 	ret
 L(n_nonzero):
 # ifdef AS_WCSLEN
-	shlq	$2, %rsi
+	shl	$2, %RSI_LP
 # endif
 
 /* Initialize long lived registers.  */
 
-	add	%rdi, %rsi
-	mov	%rsi, %r10
-	and	$-64, %r10
-	mov	%rsi, %r11
+	add	%RDI_LP, %RSI_LP
+	mov	%RSI_LP, %R10_LP
+	and	$-64, %R10_LP
+	mov	%RSI_LP, %R11_LP
 #endif
 
 	pxor	%xmm0, %xmm0
diff --git a/sysdeps/x86_64/x32/Makefile b/sysdeps/x86_64/x32/Makefile
index 2a9e20a90b..1557724b0c 100644
--- a/sysdeps/x86_64/x32/Makefile
+++ b/sysdeps/x86_64/x32/Makefile
@@ -8,10 +8,10 @@ endif
 ifeq ($(subdir),string)
 tests += tst-size_t-memchr tst-size_t-memcmp tst-size_t-memcpy \
 	 tst-size_t-memrchr tst-size_t-memset tst-size_t-strncasecmp \
-	 tst-size_t-strncmp tst-size_t-strncpy
+	 tst-size_t-strncmp tst-size_t-strncpy tst-size_t-strnlen
 endif
 
 ifeq ($(subdir),wcsmbs)
 tests += tst-size_t-wmemchr tst-size_t-wmemcmp tst-size_t-wmemset \
-	 tst-size_t-wcsncmp
+	 tst-size_t-wcsncmp tst-size_t-wcsnlen
 endif
diff --git a/sysdeps/x86_64/x32/tst-size_t-strnlen.c b/sysdeps/x86_64/x32/tst-size_t-strnlen.c
new file mode 100644
index 0000000000..690a4a8a31
--- /dev/null
+++ b/sysdeps/x86_64/x32/tst-size_t-strnlen.c
@@ -0,0 +1,72 @@
+/* Test strnlen with size_t in the lower 32 bits of 64-bit register.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifdef WIDE
+# define TEST_NAME "wcsnlen"
+#else
+# define TEST_NAME "strnlen"
+#endif /* WIDE */
+
+#include "test-size_t.h"
+
+#ifdef WIDE
+# include <wchar.h>
+# define STRNLEN wcsnlen
+# define CHAR wchar_t
+#else
+# define STRNLEN strnlen
+# define CHAR char
+#endif /* WIDE */
+
+IMPL (STRNLEN, 1)
+
+typedef size_t (*proto_t) (const CHAR *, size_t);
+
+static size_t
+__attribute__ ((noinline, noclone))
+do_strnlen (parameter_t a, parameter_t b)
+{
+  return CALL (&a, a.p, b.len);
+}
+
+static int
+test_main (void)
+{
+  test_init ();
+
+  size_t size = page_size / sizeof (CHAR);
+  parameter_t src = { { 0 }, buf2 };
+  parameter_t c = { { size }, (void *) (uintptr_t) 'a' };
+
+  int ret = 0;
+  FOR_EACH_IMPL (impl, 0)
+    {
+      src.fn = impl->fn;
+      size_t res = do_strnlen (src, c);
+      if (res != size)
+	{
+	  error (0, 0, "Wrong result in function %s: 0x%x != 0x%x",
+		 impl->name, res, size);
+	  ret = 1;
+	}
+    }
+
+  return ret ? EXIT_FAILURE : EXIT_SUCCESS;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/x86_64/x32/tst-size_t-wcsnlen.c b/sysdeps/x86_64/x32/tst-size_t-wcsnlen.c
new file mode 100644
index 0000000000..093b4bbe1b
--- /dev/null
+++ b/sysdeps/x86_64/x32/tst-size_t-wcsnlen.c
@@ -0,0 +1,20 @@
+/* Test wcsnlen with size_t in the lower 32 bits of 64-bit register.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#define WIDE 1
+#include "tst-size_t-strnlen.c"