reads: fix bug 1078

diff --git a/libbb/read.c b/libbb/read.c
index 1c2945f454101f79853044e565b5c61b83a28e31..b3648b4d749fb64360e15d8f7623af46e010eeae 100644 (file)
--- a/libbb/read.c
+++ b/libbb/read.c
@@ -86,7 +86,8 @@ char *reads(int fd, char *buffer, size_t size)
        if (p) {
                off_t offset;
                *p++ = '\0';
-               offset = (p-buffer) - size;
+               // avoid incorrect (unsigned) widening
+               offset = (off_t)(p-buffer) - (off_t)size;
                // set fd position the right after the \n
                if (offset && lseek(fd, offset, SEEK_CUR) == (off_t)-1)
                        return NULL;