From: Quentin Monnet <quentin.mon...@netronome.com>
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 <quentin.mon...@netronome.com>
---
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);
--
2.15.1
