From 3f635fb43389b54f682fc9ed2acc0b2aaf4a923d Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Mon, 4 Feb 2019 06:31:01 -0800
Subject: x86-64 memcmp: Use unsigned Jcc instructions on size [BZ #24155]

Since the size argument is unsigned. we should use unsigned Jcc
instructions, instead of signed, to check size.

Tested on x86-64 and x32, with and without --disable-multi-arch.

	[BZ #24155]
	CVE-2019-7309
	* NEWS: Updated for CVE-2019-7309.
	* sysdeps/x86_64/memcmp.S: Use RDX_LP for size.  Clear the
	upper 32 bits of RDX register for x32.  Use unsigned Jcc
	instructions, instead of signed.
	* sysdeps/x86_64/x32/Makefile (tests): Add tst-size_t-memcmp-2.
	* sysdeps/x86_64/x32/tst-size_t-memcmp-2.c: New test.
---
 sysdeps/x86_64/memcmp.S | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

(limited to 'sysdeps/x86_64/memcmp.S')

diff --git a/sysdeps/x86_64/memcmp.S b/sysdeps/x86_64/memcmp.S
index 1fc487caa5..1322bb3b92 100644
--- a/sysdeps/x86_64/memcmp.S
+++ b/sysdeps/x86_64/memcmp.S
@@ -21,14 +21,18 @@
 
 	.text
 ENTRY (memcmp)
-	test	%rdx, %rdx
+#ifdef __ILP32__
+	/* Clear the upper 32 bits.  */
+	movl	%edx, %edx
+#endif
+	test	%RDX_LP, %RDX_LP
 	jz	L(finz)
 	cmpq	$1, %rdx
-	jle	L(finr1b)
+	jbe	L(finr1b)
 	subq	%rdi, %rsi
 	movq	%rdx, %r10
 	cmpq	$32, %r10
-	jge	L(gt32)
+	jae	L(gt32)
 	/* Handle small chunks and last block of less than 32 bytes.  */
 L(small):
 	testq	$1, %r10
@@ -156,7 +160,7 @@ L(A32):
 	movq	%r11, %r10
 	andq	$-32, %r10
 	cmpq	%r10, %rdi
-        jge	L(mt16)
+        jae	L(mt16)
 	/* Pre-unroll to be ready for unrolled 64B loop.  */
 	testq	$32, %rdi
 	jz	L(A64)
@@ -178,7 +182,7 @@ L(A64):
 	movq	%r11, %r10
 	andq	$-64, %r10
 	cmpq	%r10, %rdi
-        jge	L(mt32)
+        jae	L(mt32)
 
 L(A64main):
 	movdqu    (%rdi,%rsi), %xmm0
@@ -216,7 +220,7 @@ L(mt32):
 	movq	%r11, %r10
 	andq	$-32, %r10
 	cmpq	%r10, %rdi
-        jge	L(mt16)
+        jae	L(mt16)
 
 L(A32main):
 	movdqu    (%rdi,%rsi), %xmm0
@@ -254,7 +258,7 @@ L(ATR):
 	movq	%r11, %r10
 	andq	$-32, %r10
 	cmpq	%r10, %rdi
-        jge	L(mt16)
+        jae	L(mt16)
 	testq	$16, %rdi
 	jz	L(ATR32)
 
@@ -325,7 +329,7 @@ L(ATR64main):
 	movq	%r11, %r10
 	andq	$-32, %r10
 	cmpq	%r10, %rdi
-        jge	L(mt16)
+        jae	L(mt16)
 
 L(ATR32res):
 	movdqa    (%rdi,%rsi), %xmm0
-- 
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