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From:   Christian Brauner <christian.brauner@ubuntu.com>
To:     =?UTF-8?q?St=C3=A9phane=20Graber?= <stgraber@ubuntu.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Aleksa Sarai <cyphar@cyphar.com>, Jann Horn <jannh@google.com>
Cc:     smbarber@chromium.org, Seth Forshee <seth.forshee@canonical.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Serge Hallyn <serge@hallyn.com>,
        James Morris <jmorris@namei.org>,
        Kees Cook <keescook@chromium.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Phil Estes <estesp@gmail.com>, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org,
        containers@lists.linux-foundation.org,
        linux-security-module@vger.kernel.org, linux-api@vger.kernel.org,
        Christian Brauner <christian.brauner@ubuntu.com>
Subject: [PATCH v2 21/28] posix_acl: handle fsid mappings
Date:   Fri, 14 Feb 2020 19:35:47 +0100
Message-Id: <20200214183554.1133805-22-christian.brauner@ubuntu.com>
In-Reply-To: <20200214183554.1133805-1-christian.brauner@ubuntu.com>
References: <20200214183554.1133805-1-christian.brauner@ubuntu.com>
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Switch posix_acls() to lookup fsids in the fsid mappings. If no fsid
mappings are setup the behavior is unchanged, i.e. fsids are looked up in the
id mappings.

Afaict, all filesystems that share a superblock in all user namespaces
currently do not support acls so this change should be safe to do
unconditionally.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v2 */
unchanged
---
 fs/posix_acl.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 249672bf54fe..763bba24f380 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -22,6 +22,7 @@
 #include <linux/xattr.h>
 #include <linux/export.h>
 #include <linux/user_namespace.h>
+#include <linux/fsuidgid.h>
 
 static struct posix_acl **acl_by_type(struct inode *inode, int type)
 {
@@ -692,12 +693,12 @@ static void posix_acl_fix_xattr_userns(
 	for (end = entry + count; entry != end; entry++) {
 		switch(le16_to_cpu(entry->e_tag)) {
 		case ACL_USER:
-			uid = make_kuid(from, le32_to_cpu(entry->e_id));
-			entry->e_id = cpu_to_le32(from_kuid(to, uid));
+			uid = make_kfsuid(from, le32_to_cpu(entry->e_id));
+			entry->e_id = cpu_to_le32(from_kfsuid(to, uid));
 			break;
 		case ACL_GROUP:
-			gid = make_kgid(from, le32_to_cpu(entry->e_id));
-			entry->e_id = cpu_to_le32(from_kgid(to, gid));
+			gid = make_kfsgid(from, le32_to_cpu(entry->e_id));
+			entry->e_id = cpu_to_le32(from_kfsgid(to, gid));
 			break;
 		default:
 			break;
@@ -746,12 +747,12 @@ posix_acl_from_xattr(struct user_namespace *user_ns,
 		return ERR_PTR(-EINVAL);
 	if (count == 0)
 		return NULL;
-	
+
 	acl = posix_acl_alloc(count, GFP_NOFS);
 	if (!acl)
 		return ERR_PTR(-ENOMEM);
 	acl_e = acl->a_entries;
-	
+
 	for (end = entry + count; entry != end; acl_e++, entry++) {
 		acl_e->e_tag  = le16_to_cpu(entry->e_tag);
 		acl_e->e_perm = le16_to_cpu(entry->e_perm);
@@ -765,14 +766,14 @@ posix_acl_from_xattr(struct user_namespace *user_ns,
 
 			case ACL_USER:
 				acl_e->e_uid =
-					make_kuid(user_ns,
+					make_kfsuid(user_ns,
 						  le32_to_cpu(entry->e_id));
 				if (!uid_valid(acl_e->e_uid))
 					goto fail;
 				break;
 			case ACL_GROUP:
 				acl_e->e_gid =
-					make_kgid(user_ns,
+					make_kfsgid(user_ns,
 						  le32_to_cpu(entry->e_id));
 				if (!gid_valid(acl_e->e_gid))
 					goto fail;
@@ -817,11 +818,11 @@ posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
 		switch(acl_e->e_tag) {
 		case ACL_USER:
 			ext_entry->e_id =
-				cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
+				cpu_to_le32(from_kfsuid(user_ns, acl_e->e_uid));
 			break;
 		case ACL_GROUP:
 			ext_entry->e_id =
-				cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
+				cpu_to_le32(from_kfsgid(user_ns, acl_e->e_gid));
 			break;
 		default:
 			ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
-- 
2.25.0