linux-kernel - [PATCH 04/16] capability: use vfsuid_t for vfs

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Message-Id: <20231129-idmap-fscap-refactor-v1-4-da5a26058a5b@kernel.org>
Date:   Wed, 29 Nov 2023 15:50:22 -0600
From:   "Seth Forshee (DigitalOcean)" <sforshee@...nel.org>
To:     Christian Brauner <brauner@...nel.org>,
        Serge Hallyn <serge@...lyn.com>,
        Paul Moore <paul@...l-moore.com>,
        Eric Paris <eparis@...hat.com>,
        James Morris <jmorris@...ei.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Miklos Szeredi <miklos@...redi.hu>,
        Amir Goldstein <amir73il@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-security-module@...r.kernel.org, audit@...r.kernel.org,
        linux-unionfs@...r.kernel.org,
        "Seth Forshee (DigitalOcean)" <sforshee@...nel.org>
Subject: [PATCH 04/16] capability: use vfsuid_t for vfs_caps rootids

The rootid is a kuid_t, but it contains an id which maped into a mount
idmapping, so it is really a vfsuid. This is confusing and creates
potential for misuse of the value, so change it to vfsuid_t.

Signed-off-by: Seth Forshee (DigitalOcean) <sforshee@...nel.org>
---
 include/linux/capability.h | 3 ++-
 kernel/auditsc.c           | 5 +++--
 security/commoncap.c       | 2 +-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/linux/capability.h b/include/linux/capability.h
index c24477e660fc..eb46d346bbbc 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -16,6 +16,7 @@
 #include <uapi/linux/capability.h>
 #include <linux/uidgid.h>
 #include <linux/bits.h>
+#include <linux/vfsid.h>
 
 #define _KERNEL_CAPABILITY_VERSION _LINUX_CAPABILITY_VERSION_3
 
@@ -26,7 +27,7 @@ typedef struct { u64 val; } kernel_cap_t;
 /* same as vfs_ns_cap_data but in cpu endian and always filled completely */
 struct vfs_caps {
 	__u32 magic_etc;
-	kuid_t rootid;
+	vfsuid_t rootid;
 	kernel_cap_t permitted;
 	kernel_cap_t inheritable;
 };
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 783d0bf69ca5..65691450b080 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -65,6 +65,7 @@
 #include <uapi/linux/netfilter/nf_tables.h>
 #include <uapi/linux/openat2.h> // struct open_how
 #include <uapi/linux/fanotify.h>
+#include <linux/mnt_idmapping.h>
 
 #include "audit.h"
 
@@ -2260,7 +2261,7 @@ static inline int audit_copy_fcaps(struct audit_names *name,
 	name->fcap.permitted = caps.permitted;
 	name->fcap.inheritable = caps.inheritable;
 	name->fcap.fE = !!(caps.magic_etc & VFS_CAP_FLAGS_EFFECTIVE);
-	name->fcap.rootid = caps.rootid;
+	name->fcap.rootid = AS_KUIDT(caps.rootid);
 	name->fcap_ver = (caps.magic_etc & VFS_CAP_REVISION_MASK) >>
 				VFS_CAP_REVISION_SHIFT;
 
@@ -2816,7 +2817,7 @@ int __audit_log_bprm_fcaps(struct linux_binprm *bprm,
 	ax->fcap.permitted = vcaps.permitted;
 	ax->fcap.inheritable = vcaps.inheritable;
 	ax->fcap.fE = !!(vcaps.magic_etc & VFS_CAP_FLAGS_EFFECTIVE);
-	ax->fcap.rootid = vcaps.rootid;
+	ax->fcap.rootid = AS_KUIDT(vcaps.rootid);
 	ax->fcap_ver = (vcaps.magic_etc & VFS_CAP_REVISION_MASK) >> VFS_CAP_REVISION_SHIFT;
 
 	ax->old_pcap.permitted   = old->cap_permitted;
diff --git a/security/commoncap.c b/security/commoncap.c
index cf130d81b8b4..3d045d377e5e 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -710,7 +710,7 @@ int get_vfs_caps_from_disk(struct mnt_idmap *idmap,
 	cpu_caps->permitted.val &= CAP_VALID_MASK;
 	cpu_caps->inheritable.val &= CAP_VALID_MASK;
 
-	cpu_caps->rootid = vfsuid_into_kuid(rootvfsuid);
+	cpu_caps->rootid = rootvfsuid;
 
 	return 0;
 }

-- 
2.43.0