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Message-Id: <20230301015002.2402544-1-development@efficientek.com>
Date: Tue, 28 Feb 2023 19:50:02 -0600
From: Glenn Washburn <development@...icientek.com>
To: Richard Weinberger <richard@....at>,
Anton Ivanov <anton.ivanov@...bridgegreys.com>,
Johannes Berg <johannes@...solutions.net>,
linux-um@...ts.infradead.org
Cc: Glenn Washburn <development@...icientek.com>,
linux-kernel@...r.kernel.org,
Christian Brauner <brauner@...nel.org>,
Seth Forshee <sforshee@...nel.org>,
linux-fsdevel@...r.kernel.org
Subject: [RFC PATCH v2] hostfs: handle idmapped mounts
Let hostfs handle idmapped mounts. This allows to have the same hostfs
mount appear in multiple locations with different id mappings.
root@(none):/media# id
uid=0(root) gid=0(root) groups=0(root)
root@(none):/media# mkdir mnt idmapped
root@(none):/media# mount -thostfs -o/home/user hostfs mnt
root@(none):/media# touch mnt/aaa
root@(none):/media# mount-idmapped --map-mount u:`id -u user`:0:1 --map-mount g:`id -g user`:0:1 /media/mnt /media/idmapped
root@(none):/media# ls -l mnt/aaa idmapped/aaa
-rw-r--r-- 1 root root 0 Jan 28 01:23 idmapped/aaa
-rw-r--r-- 1 user user 0 Jan 28 01:23 mnt/aaa
root@(none):/media# touch idmapped/bbb
root@(none):/media# ls -l mnt/bbb idmapped/bbb
-rw-r--r-- 1 root root 0 Jan 28 01:26 idmapped/bbb
-rw-r--r-- 1 user user 0 Jan 28 01:26 mnt/bbb
Signed-off-by: Glenn Washburn <development@...icientek.com>
---
Changes from v1:
* Rebase on to tip. The above commands work and have the results expected.
The __vfsuid_val(make_vfsuid(...)) seems ugly to get the uid_t, but it
seemed like the best one I've come across. Is there a better way?
Glenn
---
fs/hostfs/hostfs_kern.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
index c18bb50c31b6..9459da99a0db 100644
--- a/fs/hostfs/hostfs_kern.c
+++ b/fs/hostfs/hostfs_kern.c
@@ -786,7 +786,7 @@ static int hostfs_permission(struct mnt_idmap *idmap,
err = access_file(name, r, w, x);
__putname(name);
if (!err)
- err = generic_permission(&nop_mnt_idmap, ino, desired);
+ err = generic_permission(idmap, ino, desired);
return err;
}
@@ -794,13 +794,14 @@ static int hostfs_setattr(struct mnt_idmap *idmap,
struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = d_inode(dentry);
+ struct user_namespace *fs_userns = i_user_ns(inode);
struct hostfs_iattr attrs;
char *name;
int err;
int fd = HOSTFS_I(inode)->fd;
- err = setattr_prepare(&nop_mnt_idmap, dentry, attr);
+ err = setattr_prepare(idmap, dentry, attr);
if (err)
return err;
@@ -814,11 +815,11 @@ static int hostfs_setattr(struct mnt_idmap *idmap,
}
if (attr->ia_valid & ATTR_UID) {
attrs.ia_valid |= HOSTFS_ATTR_UID;
- attrs.ia_uid = from_kuid(&init_user_ns, attr->ia_uid);
+ attrs.ia_uid = __vfsuid_val(make_vfsuid(idmap, fs_userns, attr->ia_uid));
}
if (attr->ia_valid & ATTR_GID) {
attrs.ia_valid |= HOSTFS_ATTR_GID;
- attrs.ia_gid = from_kgid(&init_user_ns, attr->ia_gid);
+ attrs.ia_gid = __vfsgid_val(make_vfsgid(idmap, fs_userns, attr->ia_gid));
}
if (attr->ia_valid & ATTR_SIZE) {
attrs.ia_valid |= HOSTFS_ATTR_SIZE;
@@ -857,7 +858,7 @@ static int hostfs_setattr(struct mnt_idmap *idmap,
attr->ia_size != i_size_read(inode))
truncate_setsize(inode, attr->ia_size);
- setattr_copy(&nop_mnt_idmap, inode, attr);
+ setattr_copy(idmap, inode, attr);
mark_inode_dirty(inode);
return 0;
}
@@ -991,7 +992,7 @@ static struct file_system_type hostfs_type = {
.name = "hostfs",
.mount = hostfs_read_sb,
.kill_sb = hostfs_kill_sb,
- .fs_flags = 0,
+ .fs_flags = FS_ALLOW_IDMAP,
};
MODULE_ALIAS_FS("hostfs");
base-commit: 7fa08de735e41001a70c8ca869b2b159d74c2339
--
2.30.2
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