[PATCH] lib/lzo: port lzo fix from upstream kernel

["Teresa Gámez" <t.gamez@phytec.de>]

From: Stefan Müller-Klieser <s.mueller-klieser@phytec.de>

This ports commit 72cf90124e87d975d0b from mainline kernel to the
barebox. We were experiencing reproducible boot hang ups on one am335x
board which depended on the barebox.z size. The MLO was trapped in the
decompression code. We found some bug reports around the lzo
decompressor in kernel and u-boot. With this version we cannot reproduce
the hang up any more.

Signed-off-by: Stefan Müller-Klieser <s.mueller-klieser@phytec.de>
---
 lib/lzo/lzo1x_decompress_safe.c | 105 ++++++++++++++++++++++------------------
 1 file changed, 58 insertions(+), 47 deletions(-)

diff --git a/lib/lzo/lzo1x_decompress_safe.c b/lib/lzo/lzo1x_decompress_safe.c
index 48bedba..2c2ded1 100644
--- a/lib/lzo/lzo1x_decompress_safe.c
+++ b/lib/lzo/lzo1x_decompress_safe.c
@@ -16,31 +16,21 @@
 #include <lzo.h>
 #include "lzodefs.h"
 
-#define HAVE_IP(t, x)					\
-	(((size_t)(ip_end - ip) >= (size_t)(t + x)) &&	\
-	 (((t + x) >= t) && ((t + x) >= x)))
-
-#define HAVE_OP(t, x)					\
-	(((size_t)(op_end - op) >= (size_t)(t + x)) &&	\
-	 (((t + x) >= t) && ((t + x) >= x)))
-
-#define NEED_IP(t, x)					\
-	do {						\
-		if (!HAVE_IP(t, x))			\
-			goto input_overrun;		\
-	} while (0)
-
-#define NEED_OP(t, x)					\
-	do {						\
-		if (!HAVE_OP(t, x))			\
-			goto output_overrun;		\
-	} while (0)
-
-#define TEST_LB(m_pos)					\
-	do {						\
-		if ((m_pos) < out)			\
-			goto lookbehind_overrun;	\
-	} while (0)
+#define HAVE_IP(x)      ((size_t)(ip_end - ip) >= (size_t)(x))
+#define HAVE_OP(x)      ((size_t)(op_end - op) >= (size_t)(x))
+#define NEED_IP(x)      if (!HAVE_IP(x)) goto input_overrun
+#define NEED_OP(x)      if (!HAVE_OP(x)) goto output_overrun
+#define TEST_LB(m_pos)  if ((m_pos) < out) goto lookbehind_overrun
+
+/* This MAX_255_COUNT is the maximum number of times we can add 255 to a base
+ * count without overflowing an integer. The multiply will overflow when
+ * multiplying 255 by more than MAXINT/255. The sum will overflow earlier
+ * depending on the base count. Since the base count is taken from a u8
+ * and a few bits, it is safe to assume that it will always be lower than
+ * or equal to 2*255, thus we can always prevent any overflow by accepting
+ * two less 255 steps. See Documentation/lzo.txt for more information.
+ */
+#define MAX_255_COUNT      ((((size_t)~0) / 255) - 2)
 
 int lzo1x_decompress_safe(const unsigned char *in, size_t in_len,
 			  unsigned char *out, size_t *out_len)
@@ -72,17 +62,24 @@ int lzo1x_decompress_safe(const unsigned char *in, size_t in_len,
 		if (t < 16) {
 			if (likely(state == 0)) {
 				if (unlikely(t == 0)) {
+					size_t offset;
+					const unsigned char *ip_last = ip;
+
 					while (unlikely(*ip == 0)) {
-						t += 255;
 						ip++;
-						NEED_IP(1, 0);
+						NEED_IP(1);
 					}
-					t += 15 + *ip++;
+					offset = ip - ip_last;
+					if (unlikely(offset > MAX_255_COUNT))
+						return LZO_E_ERROR;
+
+					offset = (offset << 8) - offset;
+					t += offset + 15 + *ip++;
 				}
 				t += 3;
 copy_literal_run:
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
-				if (likely(HAVE_IP(t, 15) && HAVE_OP(t, 15))) {
+				if (likely(HAVE_IP(t + 15) && HAVE_OP(t + 15))) {
 					const unsigned char *ie = ip + t;
 					unsigned char *oe = op + t;
 					do {
@@ -98,8 +95,8 @@ copy_literal_run:
 				} else
 #endif
 				{
-					NEED_OP(t, 0);
-					NEED_IP(t, 3);
+					NEED_OP(t);
+					NEED_IP(t + 3);
 					do {
 						*op++ = *ip++;
 					} while (--t > 0);
@@ -112,7 +109,7 @@ copy_literal_run:
 				m_pos -= t >> 2;
 				m_pos -= *ip++ << 2;
 				TEST_LB(m_pos);
-				NEED_OP(2, 0);
+				NEED_OP(2);
 				op[0] = m_pos[0];
 				op[1] = m_pos[1];
 				op += 2;
@@ -133,13 +130,20 @@ copy_literal_run:
 		} else if (t >= 32) {
 			t = (t & 31) + (3 - 1);
 			if (unlikely(t == 2)) {
+				size_t offset;
+				const unsigned char *ip_last = ip;
+
 				while (unlikely(*ip == 0)) {
-					t += 255;
 					ip++;
-					NEED_IP(1, 0);
+					NEED_IP(1);
 				}
-				t += 31 + *ip++;
-				NEED_IP(2, 0);
+				offset = ip - ip_last;
+				if (unlikely(offset > MAX_255_COUNT))
+					return LZO_E_ERROR;
+
+				offset = (offset << 8) - offset;
+				t += offset + 31 + *ip++;
+				NEED_IP(2);
 			}
 			m_pos = op - 1;
 			next = get_unaligned_le16(ip);
@@ -151,13 +155,20 @@ copy_literal_run:
 			m_pos -= (t & 8) << 11;
 			t = (t & 7) + (3 - 1);
 			if (unlikely(t == 2)) {
+				size_t offset;
+				const unsigned char *ip_last = ip;
+
 				while (unlikely(*ip == 0)) {
-					t += 255;
 					ip++;
-					NEED_IP(1, 0);
+					NEED_IP(1);
 				}
-				t += 7 + *ip++;
-				NEED_IP(2, 0);
+				offset = ip - ip_last;
+				if (unlikely(offset > MAX_255_COUNT))
+					return LZO_E_ERROR;
+
+				offset = (offset << 8) - offset;
+				t += offset + 7 + *ip++;
+				NEED_IP(2);
 			}
 			next = get_unaligned_le16(ip);
 			ip += 2;
@@ -171,7 +182,7 @@ copy_literal_run:
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
 		if (op - m_pos >= 8) {
 			unsigned char *oe = op + t;
-			if (likely(HAVE_OP(t, 15))) {
+			if (likely(HAVE_OP(t + 15))) {
 				do {
 					COPY8(op, m_pos);
 					op += 8;
@@ -181,7 +192,7 @@ copy_literal_run:
 					m_pos += 8;
 				} while (op < oe);
 				op = oe;
-				if (HAVE_IP(6, 0)) {
+				if (HAVE_IP(6)) {
 					state = next;
 					COPY4(op, ip);
 					op += next;
@@ -189,7 +200,7 @@ copy_literal_run:
 					continue;
 				}
 			} else {
-				NEED_OP(t, 0);
+				NEED_OP(t);
 				do {
 					*op++ = *m_pos++;
 				} while (op < oe);
@@ -198,7 +209,7 @@ copy_literal_run:
 #endif
 		{
 			unsigned char *oe = op + t;
-			NEED_OP(t, 0);
+			NEED_OP(t);
 			op[0] = m_pos[0];
 			op[1] = m_pos[1];
 			op += 2;
@@ -211,15 +222,15 @@ match_next:
 		state = next;
 		t = next;
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
-		if (likely(HAVE_IP(6, 0) && HAVE_OP(4, 0))) {
+		if (likely(HAVE_IP(6) && HAVE_OP(4))) {
 			COPY4(op, ip);
 			op += t;
 			ip += t;
 		} else
 #endif
 		{
-			NEED_IP(t, 3);
-			NEED_OP(t, 0);
+			NEED_IP(t + 3);
+			NEED_OP(t);
 			while (t > 0) {
 				*op++ = *ip++;
 				t--;
-- 
1.9.1


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