From: hridya@google.com (Hridya Valsaraju)
Subject: [PATCH v3 2/2] binder: Validate the default binderfs device names.
Date: Fri, 9 Aug 2019 11:41:12 -0700 [thread overview]
Message-ID: <CA+wgaPPK0fY2a+pCEFHrw8p8WCb459yw41s_6xppWFfEa=P7Og@mail.gmail.com> (raw)
In-Reply-To: <20190809181439.qrs2k7l23ot4am4s@wittgenstein>
On Fri, Aug 9, 2019 at 11:14 AM Christian Brauner
<christian.brauner@ubuntu.com> wrote:
>
> On Fri, Aug 09, 2019@04:55:08PM +0200, Greg Kroah-Hartman wrote:
> > On Thu, Aug 08, 2019@03:27:26PM -0700, Hridya Valsaraju wrote:
> > > Length of a binderfs device name cannot exceed BINDERFS_MAX_NAME.
> > > This patch adds a check in binderfs_init() to ensure the same
> > > for the default binder devices that will be created in every
> > > binderfs instance.
> > >
> > > Co-developed-by: Christian Brauner <christian.brauner at ubuntu.com>
> > > Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
> > > Signed-off-by: Hridya Valsaraju <hridya at google.com>
> > > ---
> > > drivers/android/binderfs.c | 12 ++++++++++++
> > > 1 file changed, 12 insertions(+)
> > >
> > > diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
> > > index aee46dd1be91..55c5adb87585 100644
> > > --- a/drivers/android/binderfs.c
> > > +++ b/drivers/android/binderfs.c
> > > @@ -570,6 +570,18 @@ static struct file_system_type binder_fs_type = {
> > > int __init init_binderfs(void)
> > > {
> > > int ret;
> > > + const char *name;
> > > + size_t len;
> > > +
> > > + /* Verify that the default binderfs device names are valid. */
> >
> > And by "valid" you only mean "not bigger than BINDERFS_MAX_NAME, right?
> >
> > > + name = binder_devices_param;
> > > + for (len = strcspn(name, ","); len > 0; len = strcspn(name, ",")) {
> > > + if (len > BINDERFS_MAX_NAME)
> > > + return -E2BIG;
> > > + name += len;
> > > + if (*name == ',')
> > > + name++;
> > > + }
> >
> > We already tokenize the binderfs device names in binder_init(), why not
> > check this there instead? Parsing the same string over and over isn't
> > the nicest.
>
> non-binderfs binder devices do not have their limit set to
> BINDERFS_NAME_MAX. That's why the check has likely been made specific to
> binderfs binder devices which do have that limit.
Thank you Greg and Christian, for taking another look. Yes,
non-binderfs binder devices not having this limitation is the reason
why the check was made specific to binderfs devices. Also, when
CONFIG_ANDROID_BINDERFS is set, patch 1/2 disabled the same string
being parsed in binder_init().
>
> But, in practice, 255 is the standard path-part limit that no-one really
> exceeds especially not for stuff such as device nodes which usually have
> rather standard naming schemes (e.g. binder, vndbinder, hwbinder, etc.).
> So yes, we can move that check before both the binderfs binder device
> and non-binderfs binder device parsing code and treat it as a generic
> check.
> Then we can also backport that check as you requested in the other mail.
> Unless Hridya or Todd have objections, of course.
I do not have any objections to adding a generic check in binder_init() instead.
>
> Christian
next prev parent reply other threads:[~2019-08-09 18:41 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-08 22:27 [PATCH v3 0/2] Add default binderfs devices Hridya Valsaraju
2019-08-08 22:27 ` [PATCH v3 1/2] binder: Add default binder devices through binderfs when configured Hridya Valsaraju
2019-08-09 14:50 ` Greg Kroah-Hartman
2019-08-09 18:22 ` Christian Brauner
2019-08-09 20:08 ` Hridya Valsaraju
2019-08-15 16:28 ` Joel Fernandes
2019-08-15 16:30 ` Joel Fernandes
2019-08-08 22:27 ` [PATCH v3 2/2] binder: Validate the default binderfs device names Hridya Valsaraju
2019-08-09 14:51 ` Greg Kroah-Hartman
2019-08-09 14:55 ` Greg Kroah-Hartman
2019-08-09 18:14 ` Christian Brauner
2019-08-09 18:41 ` Hridya Valsaraju [this message]
2019-09-04 7:19 ` Greg Kroah-Hartman
2019-09-04 10:44 ` Christian Brauner
2019-09-04 10:49 ` Greg Kroah-Hartman
2019-09-04 11:07 ` Christian Brauner
2019-08-15 16:31 ` Joel Fernandes
2019-08-15 16:00 ` [PATCH v3 0/2] Add default binderfs devices Greg Kroah-Hartman
2019-09-04 11:07 ` [RESEND PATCH " Christian Brauner
2019-09-04 11:07 ` [RESEND PATCH v3 1/2] binder: Add default binder devices through binderfs when configured Christian Brauner
2019-09-04 11:07 ` [RESEND PATCH v3 2/2] binder: Validate the default binderfs device names Christian Brauner
2019-09-04 11:18 ` [RESEND PATCH v3 0/2] Add default binderfs devices Greg KH
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