On Mon, Sep 23, 2024, at 19:34, Lorenzo Stoakes wrote:

On Mon, Sep 23, 2024 at 11:56:06AM GMT, Shakeel Butt wrote:

+	/* Require PTRACE_MODE_READ to avoid leaking ASLR metadata. */
+	mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
+	if (IS_ERR_OR_NULL(mm)) {
+		ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
+		goto release_task;
+	}

Any chance we can fix mm_access() to not be able to return
a NULL pointer and an error pointer?  IS_ERR_OR_NULL() is
usually an indication of a confusing API, and this is
clearly one of them, given that only one of the
callers actually wants the NULL value instead of -ESRCH.

    Arnd