fix out of bounds write for zero length buffer in gethostname

[musl] / src / unistd / getcwd.c

diff --git a/src/unistd/getcwd.c b/src/unistd/getcwd.c
index a7b925d..103fbbb 100644 (file)
--- a/src/unistd/getcwd.c
+++ b/src/unistd/getcwd.c
@@ -14,6 +14,12 @@ char *getcwd(char *buf, size_t size)
                errno = EINVAL;
                return 0;
        }
-       if (syscall(SYS_getcwd, buf, size) < 0) return 0;
+       long ret = syscall(SYS_getcwd, buf, size);
+       if (ret < 0)
+               return 0;
+       if (ret == 0 || buf[0] != '/') {
+               errno = ENOENT;
+               return 0;
+       }
        return buf == tmp ? strdup(buf) : buf;
 }