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-rw-r--r--lib/lzo/lzo1x_decompress_safe.c43
1 files changed, 37 insertions, 6 deletions
diff --git a/lib/lzo/lzo1x_decompress_safe.c b/lib/lzo/lzo1x_decompress_safe.c
index 569985d522d5..a1c387f6afba 100644
--- a/lib/lzo/lzo1x_decompress_safe.c
+++ b/lib/lzo/lzo1x_decompress_safe.c
@@ -25,6 +25,16 @@
#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)
{
@@ -55,12 +65,19 @@ 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);
}
- 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:
@@ -116,12 +133,19 @@ 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);
}
- t += 31 + *ip++;
+ 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;
@@ -134,12 +158,19 @@ 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);
}
- t += 7 + *ip++;
+ 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);

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