On Wed, Apr 17, 2019 at 11:13 PM Al Viro viro@zeniv.linux.org.uk 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