From bb35a6ef7da492e7df1fe8772716ff88c172b4cc Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Thu, 10 Dec 2015 22:33:49 +0100 Subject: [PATCH] bpf, inode: allow for rename and link ops Add support for renaming and hard links to the fs. Most of this can be implemented by using simple library operations under the same constraints that we don't use a reserved name like elsewhere. Linking can be useful to share/manage things like maps across subsystem users. It works within the file system boundary, but is not allowed for directories. Symbolic links are explicitly not implemented here, as it can be better done already by doing bind mounts inside bpf fs to set up shared directories f.e. useful when using volumes in docker containers that map a private working directory into /sys/fs/bpf/ which contains itself a bind mounted path from the host's /sys/fs/bpf/ mount that is shared among multiple containers. For single maps instead of whole directory, hard links can be easily used to do the same. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- kernel/bpf/inode.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c index 5a8a797d50b7..f2ece3c174a5 100644 --- a/kernel/bpf/inode.c +++ b/kernel/bpf/inode.c @@ -187,11 +187,31 @@ static int bpf_mkobj(struct inode *dir, struct dentry *dentry, umode_t mode, } } +static int bpf_link(struct dentry *old_dentry, struct inode *dir, + struct dentry *new_dentry) +{ + if (bpf_dname_reserved(new_dentry)) + return -EPERM; + + return simple_link(old_dentry, dir, new_dentry); +} + +static int bpf_rename(struct inode *old_dir, struct dentry *old_dentry, + struct inode *new_dir, struct dentry *new_dentry) +{ + if (bpf_dname_reserved(new_dentry)) + return -EPERM; + + return simple_rename(old_dir, old_dentry, new_dir, new_dentry); +} + static const struct inode_operations bpf_dir_iops = { .lookup = simple_lookup, .mknod = bpf_mkobj, .mkdir = bpf_mkdir, .rmdir = simple_rmdir, + .rename = bpf_rename, + .link = bpf_link, .unlink = simple_unlink, }; -- 2.20.1