kern/cbuf: fix very unlikely but potential integer overflows

1 files changed, 2 insertions, 2 deletions

diff --git a/kern/cbuf.c b/kern/cbuf.c
index f00532ef..ea848c56 100644
--- a/kern/cbuf.c
+++ b/kern/cbuf.c
@@ -99,7 +99,7 @@ cbuf_write(struct cbuf *cbuf, size_t index, const void *buf, size_t size)
     end = start + size;
     buf_end = cbuf->buf + cbuf->capacity;
 
-    if (end > buf_end) {
+    if ((end <= cbuf->buf) || (end > buf_end)) {
         skip = buf_end - start;
         memcpy(start, buf, skip);
         buf += skip;
@@ -133,7 +133,7 @@ cbuf_read(const struct cbuf *cbuf, size_t index, void *buf, size_t *sizep)
     end = start + *sizep;
     buf_end = cbuf->buf + cbuf->capacity;
 
-    if (end <= buf_end) {
+    if ((end > cbuf->buf) && (end <= buf_end)) {
         size = *sizep;
     } else {
         size = buf_end - start;