Messages in this thread | | | From | Carlos Llamas <> | Date | Thu, 8 Jul 2021 10:33:35 -0600 | Subject | Re: [PATCH] ANDROID: binderfs: add capabilities support |
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On Wed, Jul 7, 2021 at 10:59 AM Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote: > > On Wed, Jul 07, 2021 at 04:24:19PM +0000, Carlos Llamas wrote: > > Provide userspace with a mechanism to discover binder driver > > capabilities to refrain from using these unsupported features > > in the first place. Note that older capabilities are assumed > > to be supported and only new ones will be added. > > What defines "new" vs. "old"? Where was the line drawn?
Any feature after "one way spam" may be added to the capabilities. I'll amend the commit message to indicate this.
> > > Signed-off-by: Carlos Llamas <cmllamas@google.com> > > --- > > drivers/android/binderfs.c | 45 ++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 45 insertions(+) > > > > diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c > > index e80ba93c62a9..f793887f6dc8 100644 > > --- a/drivers/android/binderfs.c > > +++ b/drivers/android/binderfs.c > > @@ -58,6 +58,10 @@ enum binderfs_stats_mode { > > binderfs_stats_mode_global, > > }; > > > > +struct binder_capabilities { > > + bool oneway_spam; > > +}; > > + > > static const struct constant_table binderfs_param_stats[] = { > > { "global", binderfs_stats_mode_global }, > > {} > > @@ -69,6 +73,10 @@ static const struct fs_parameter_spec binderfs_fs_parameters[] = { > > {} > > }; > > > > +static struct binder_capabilities binder_caps = { > > + .oneway_spam = true, > > +}; > > + > > static inline struct binderfs_info *BINDERFS_SB(const struct super_block *sb) > > { > > return sb->s_fs_info; > > @@ -583,6 +591,39 @@ static struct dentry *binderfs_create_dir(struct dentry *parent, > > return dentry; > > } > > > > +static int binder_caps_show(struct seq_file *m, void *unused) > > +{ > > + bool *cap = m->private; > > + > > + seq_printf(m, "%d\n", *cap); > > + > > + return 0; > > +} > > +DEFINE_SHOW_ATTRIBUTE(binder_caps); > > + > > +static int init_binder_caps(struct super_block *sb) > > +{ > > + struct dentry *dentry, *root; > > + int ret = 0; > > + > > + root = binderfs_create_dir(sb->s_root, "caps"); > > + if (IS_ERR(root)) { > > + ret = PTR_ERR(root); > > + goto out; > > + } > > + > > + dentry = binderfs_create_file(root, "oneway_spam", > > + &binder_caps_fops, > > + &binder_caps.oneway_spam); > > + if (IS_ERR(dentry)) { > > + ret = PTR_ERR(dentry); > > + goto out; > > If this fails, you still report that an error happened, yet you do not > remove the directory? Is that intended?
Propagating an error in this case will kill the super block along with the capabilities entries. At a user level the binderfs will fail to be mounted, so anything created up until this point is removed.
> > And where is this new file documented? Where are the existing binderfs > files documented?
oh! we do have "Documentation/admin-guide/binderfs.rst". I'll add a brief explanation of these new capabilities files there.
> > thanks, > > greg k-h
thanks, carlos llamas
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