From 6d8cb045cde681e64a5ed80a2ab70be831a7f9b0 Mon Sep 17 00:00:00 2001 From: Quentin Monnet Date: Thu, 8 Mar 2018 23:46:33 -0800 Subject: [PATCH] bpf: comment why dots in filenames under BPF virtual FS are not allowed When pinning a file under the BPF virtual file system (traditionally /sys/fs/bpf), using a dot in the name of the location to pin at is not allowed. For example, trying to pin at "/sys/fs/bpf/foo.bar" will be rejected with -EPERM. This check was introduced at the same time as the BPF file system itself, with commit b2197755b263 ("bpf: add support for persistent maps/progs"). At this time, it was checked in a function called "bpf_dname_reserved()", which made clear that using a dot was reserved for future extensions. This function disappeared and the check was moved elsewhere with commit 0c93b7d85d40 ("bpf: reject invalid names right in ->lookup()"), and the meaning of the dot ban was lost. The present commit simply adds a comment in the source to explain to the reader that the usage of dots is reserved for future usage. Signed-off-by: Quentin Monnet Signed-off-by: Daniel Borkmann --- kernel/bpf/inode.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c index 81e2f6995adb..bf6da59ae0d0 100644 --- a/kernel/bpf/inode.c +++ b/kernel/bpf/inode.c @@ -178,6 +178,9 @@ static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg) static struct dentry * bpf_lookup(struct inode *dir, struct dentry *dentry, unsigned flags) { + /* Dots in names (e.g. "/sys/fs/bpf/foo.bar") are reserved for future + * extensions. + */ if (strchr(dentry->d_name.name, '.')) return ERR_PTR(-EPERM);