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xattr: handle idmapped mounts

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When interacting with extended attributes the vfs verifies that the
caller is privileged over the inode with which the extended attribute is
associated. For posix access and posix default extended attributes a uid
or gid can be stored on-disk. Let the functions handle posix extended
attributes on idmapped mounts. If the inode is accessed through an
idmapped mount we need to map it according to the mount's user
namespace. Afterwards the checks are identical to non-idmapped mounts.
This has no effect for e.g. security xattrs since they don't store uids
or gids and don't perform permission checks on them like posix acls do.

Link: https://lore.kernel.org/r/20210121131959.646623-10-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Tycho Andersen <tycho@tycho.pizza>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
This commit is contained in:
Tycho Andersen
2021-01-21 14:19:28 +01:00
committed by Christian Brauner
parent e65ce2a50c
commit c7c7a1a18a
19 changed files with 160 additions and 124 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
fs/ecryptfs/inode.c
View File

@@ -1024,7 +1024,8 @@ ecryptfs_setxattr(struct dentry *dentry, struct inode *inode,
rc = -EOPNOTSUPP;
goto out;
}
rc = vfs_setxattr(lower_dentry, name, value, size, flags);
rc = vfs_setxattr(&init_user_ns, lower_dentry, name, value, size,
flags);
if (!rc && inode)
fsstack_copy_attr_all(inode, d_inode(lower_dentry));
out:
@@ -1089,7 +1090,7 @@ static int ecryptfs_removexattr(struct dentry *dentry, struct inode *inode,
goto out;
}
inode_lock(lower_inode);
rc = __vfs_removexattr(lower_dentry, name);
rc = __vfs_removexattr(&init_user_ns, lower_dentry, name);
inode_unlock(lower_inode);
out:
return rc;