Re: [PATCH 5.10 130/154] block: Check ADMIN before NICE for IOPRIO_CLASS_RT
From: Jari Ruusu <hidden>
Date: 2021-11-24 14:39:17
Also in:
linux-security-module, lkml, selinux
Greg Kroah-Hartman wrote:
From: Alistair Delva <redacted> commit 94c4b4fd25e6c3763941bdec3ad54f2204afa992 upstream.
[SNIP]
quoted hunk ↗ jump to hunk
--- a/block/ioprio.c +++ b/block/ioprio.c@@ -69,7 +69,14 @@ int ioprio_check_cap(int ioprio) switch (class) { case IOPRIO_CLASS_RT: - if (!capable(CAP_SYS_NICE) && !capable(CAP_SYS_ADMIN)) + /* + * Originally this only checked for CAP_SYS_ADMIN, + * which was implicitly allowed for pid 0 by security + * modules such as SELinux. Make sure we check + * CAP_SYS_ADMIN first to avoid a denial/avc for + * possibly missing CAP_SYS_NICE permission. + */ + if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_NICE)) return -EPERM; fallthrough; /* rt has prio field too */
What exactly is above patch trying to fix? It does not change control flow at all, and added comment is misleading. -- Jari Ruusu 4096R/8132F189 12D6 4C3A DCDA 0AA4 27BD ACDF F073 3C80 8132 F189