From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Date: Wed, 17 Apr 2019 22:03:07 +0000 Subject: Re: [PATCH v3 02/26] compat_ioctl: move simple ppp command handling into driver Message-Id: List-Id: References: <20190416202013.4034148-1-arnd@arndb.de> <20190416202013.4034148-3-arnd@arndb.de> <20190417211303.GU2217@ZenIV.linux.org.uk> In-Reply-To: <20190417211303.GU2217@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Al Viro Cc: Linux FS-devel Mailing List , y2038 Mailman List , Linux Kernel Mailing List , Paul Mackerras , "David S. Miller" , Michal Ostrowski , Dmitry Kozlov , James Chapman , linux-ppp@vger.kernel.org, Networking On Wed, Apr 17, 2019 at 11:13 PM Al Viro wrote: > > On Tue, Apr 16, 2019 at 10:19:40PM +0200, Arnd Bergmann wrote: > > diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c > > index c708400fff4a..04252c3492ee 100644 > > --- a/drivers/net/ppp/ppp_generic.c > > +++ b/drivers/net/ppp/ppp_generic.c > > @@ -899,6 +899,7 @@ static const struct file_operations ppp_device_fops = { > > .write = ppp_write, > > .poll = ppp_poll, > > .unlocked_ioctl = ppp_ioctl, > > + .compat_ioctl = ppp_ioctl, > > Oh? What happens on e.g. s390 with something like PPPIOCNEWUNIT? > Current kernel: > * no ->compat_ioctl() > * ->unlock_ioctl() is present > * found by compat_ioctl_check_table() > * pass (unsigned long)compat_ptr(arg) to do_vfs_ioctl() > * pass that to ppp_ioctl() > * pass that to ppp_unattached_ioctl() > * fetch int from (int __user *)compat_ptr(arg) > > With your patch: > * call ppp_ioctl() > * pass arg to ppp_unattached_ioctl() > * fetch int from (int __user *)arg > > AFAICS, that's broken... Correct. I had added this patch to the series from an older set of patches (predating the compat_ptr_ioctl() series) , and did not check for this issue again. When I originally created the patch, I assumed that even on s390 it would be no problem. > Looking at that ppp_ioctl(), > pointer to arch-independent type or ignored: > PPPIOCNEWUNIT PPPIOCATTACH PPPIOCATTCHAN PPPIOCSMRU PPPIOCSFLAGS > PPPIOCGFLAGS PPPIOCGUNIT PPPIOCSDEBUG PPPIOCSMAXCID PPPIOCCONNECT > PPPIOCGDEBUG PPPIOCSMAXCID PPPIOCSMRRU > PPPIOCDETACH PPPIOCDISCONN > PPPIOCGASYNCMAP PPPIOCSASYNCMAP PPPIOCGRASYNCMAP PPPIOCSRASYNCMAP > PPPIOCGXASYNCMAP PPPIOCSXASYNCMAP > PPPIOCGNPMODE PPPIOCSNPMODE > pointer to struct ppp_option_data (with further pointer-chasing in it): > PPPIOCSCOMPRESS > pointer to struct ppp_idle: > PPPIOCGIDLE > pointer to struct sock_filter (with hidden pointer-chasing, AFAICS): > PPPIOCSPASS PPPIOCSACTIVE > > Pretty much all of them take pointers. What's more, reaction to > unknown is -ENOTTY, not -ENOIOCTLCM, so that patch will have > prevent the translated ones from reaching do_ioctl_trans() Good point, this patch sequence does break bisection. > What am I missing here? Why not simply do > > compat_ppp_ioctl() > { > PPPIOCSCOMPRESS32 => deal with it > PPPIOCGIDLE32 => deal with it > PPPIOCSPASS32 / PPPIOCSACTIVE32 => deal with it > default: pass compat_ptr(arg) to ppp_ioctl() and be done with that > } > > with BPF-related bits (both compat and native) taken to e.g. net/core/bpf-ppp.c, > picked by both generic and isdn? IDGI... I was trying to unify the native and compat code paths as much as possible here. Handling the four PPPIO*32 commands in compat_ppp_ioctl would either require duplicating large chunks of ppp_ioctl, or keeping the extra compat_alloc_user_space() copy from the existing implementation. I'll try to come up with a different way to structure the patches. Arnd