From: Arnd Bergmann <arnd@arndb.de>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
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Subject: Re: [PATCH v3 12/26] compat_ioctl: move more drivers to compat_ptr_ioctl
Date: Fri, 26 Apr 2019 09:46:13 +0200 [thread overview]
Message-ID: <CAK8P3a3CzKLvpUiVV_k__kkaZ=wg2fqnFEzWYL9qNwBfxMKZ9w@mail.gmail.com> (raw)
In-Reply-To: <5511420228cb38d08a67c0f6a614b7671d7d23d4.camel@sipsolutions.net>
On Thu, Apr 25, 2019 at 11:25 PM Johannes Berg
<johannes@sipsolutions.net> wrote:
> On Thu, 2019-04-25 at 17:55 +0200, Arnd Bergmann wrote:
> > On Thu, Apr 25, 2019 at 5:35 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> > >
> > > On Thu, Apr 25, 2019 at 12:21:53PM -0300, Mauro Carvalho Chehab wrote:
> > >
> > > > If I understand your patch description well, using compat_ptr_ioctl
> > > > only works if the driver is not for s390, right?
> > >
> > > No; s390 is where "oh, just set ->compat_ioctl same as ->unlocked_ioctl
> > > and be done with that; compat_ptr() is a no-op anyway" breaks. IOW,
> > > s390 is the reason for having compat_ptr_ioctl() in the first place;
> > > that thing works on all biarch architectures, as long as all stuff
> > > handled by ->ioctl() takes pointer to arch-independent object as
> > > argument. IOW,
> > > argument ignored => OK
> > > any arithmetical type => no go, compat_ptr() would bugger it
> > > pointer to int => OK
> > > pointer to string => OK
> > > pointer to u64 => OK
> > > pointer to struct {u64 addr; char s[11];} => OK
> >
> > To be extra pedantic, the 'struct {u64 addr; char s[11];} '
> > case is also broken on x86, because sizeof (obj) is smaller
> > on i386, even though the location of the members are
> > the same. i.e. you can copy_from_user() this
>
> Actually, you can't even do that because the struct might sit at the end
> of a page and then you'd erroneously fault in this case.
>
> We had this a while ago with struct ifreq, see commit 98406133dd and its
> parents.
Yes, you are right. Very rare to hit with real-life code, but easily
reproduced by intentionally hitting it and clearly a bug.
As the saying goes
| the difference between "always works" and "almost always works"
| is called data corruption
here the difference is an -EFAULT.
Arnd
next prev parent reply other threads:[~2019-04-26 7:46 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-16 20:19 [PATCH v3 00/26] compat_ioctl: cleanups Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 01/26] compat_ioctl: pppoe: fix PPPOEIOCSFWD handling Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 02/26] compat_ioctl: move simple ppp command handling into driver Arnd Bergmann
2019-04-17 21:13 ` Al Viro
2019-04-17 22:03 ` Arnd Bergmann
2019-04-17 23:53 ` Al Viro
2019-04-18 5:57 ` Al Viro
2019-04-18 15:14 ` Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 03/26] compat_ioctl: avoid unused function warning for do_ioctl Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 04/26] compat_ioctl: move PPPIOCSCOMPRESS32 to ppp-generic.c Arnd Bergmann
2019-04-17 21:16 ` Al Viro
2019-04-17 21:44 ` Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 05/26] compat_ioctl: move PPPIOCSPASS32/PPPIOCSACTIVE32 to ppp_generic.c Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 06/26] compat_ioctl: handle PPPIOCGIDLE for 64-bit time_t Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 07/26] compat_ioctl: move rtc handling into rtc-dev.c Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 08/26] compat_ioctl: add compat_ptr_ioctl() Arnd Bergmann
2019-04-17 21:19 ` Al Viro
2019-04-17 21:34 ` Arnd Bergmann
2019-04-16 20:19 ` [PATCH v3 09/26] compat_ioctl: move drivers to compat_ptr_ioctl Arnd Bergmann
2019-04-16 20:31 ` Jiri Kosina
2019-04-18 11:10 ` Stefan Hajnoczi
2019-04-19 23:16 ` Michael S. Tsirkin
2019-04-16 20:19 ` [PATCH v3 10/26] compat_ioctl: use correct compat_ptr() translation in drivers Arnd Bergmann
2019-04-17 21:21 ` Al Viro
2019-04-16 20:19 ` [PATCH v3 11/26] ceph: fix compat_ioctl for ceph_dir_operations Arnd Bergmann
2019-04-17 21:23 ` Al Viro
2019-04-17 21:31 ` Arnd Bergmann
2019-04-16 20:25 ` [PATCH v3 12/26] compat_ioctl: move more drivers to compat_ptr_ioctl Arnd Bergmann
2019-04-16 20:25 ` [PATCH v3 13/26] compat_ioctl: move tape handling into drivers Arnd Bergmann
2019-04-16 20:25 ` [PATCH v3 14/26] compat_ioctl: move ATYFB_CLK handling to atyfb driver Arnd Bergmann
2019-04-17 21:27 ` Al Viro
2019-04-17 21:28 ` Al Viro
2019-05-06 13:37 ` Bartlomiej Zolnierkiewicz
2019-04-16 20:25 ` [PATCH v3 15/26] compat_ioctl: move isdn/capi ioctl translation into driver Arnd Bergmann
2019-04-16 20:25 ` [PATCH v3 16/26] compat_ioctl: move rfcomm handlers " Arnd Bergmann
2019-04-16 20:25 ` [PATCH v3 17/26] compat_ioctl: move hci_sock " Arnd Bergmann
2019-04-16 20:25 ` [PATCH v3 18/26] compat_ioctl: remove HCIUART handling Arnd Bergmann
2019-04-16 20:25 ` [PATCH v3 19/26] compat_ioctl: remove HIDIO translation Arnd Bergmann
2019-04-25 15:21 ` [PATCH v3 12/26] compat_ioctl: move more drivers to compat_ptr_ioctl Mauro Carvalho Chehab
2019-04-25 15:32 ` Arnd Bergmann
2019-04-25 15:35 ` Al Viro
2019-04-25 15:53 ` Mauro Carvalho Chehab
2019-04-25 15:55 ` Arnd Bergmann
2019-04-25 16:42 ` Al Viro
2019-04-25 21:25 ` Johannes Berg
2019-04-26 7:46 ` Arnd Bergmann [this message]
2019-04-16 20:28 ` [PATCH v3 20/26] compat_ioctl: remove translation for sound ioctls Arnd Bergmann
2019-04-16 20:28 ` [PATCH v3 21/26] compat_ioctl: remove IGNORE_IOCTL() Arnd Bergmann
2019-04-16 20:28 ` [PATCH v3 22/26] compat_ioctl: remove /dev/random commands Arnd Bergmann
2019-04-16 20:28 ` [PATCH v3 23/26] compat_ioctl: remove joystick ioctl translation Arnd Bergmann
2019-04-16 20:28 ` [PATCH v3 24/26] compat_ioctl: remove PCI " Arnd Bergmann
2019-04-16 20:28 ` [PATCH v3 25/26] compat_ioctl: remove /dev/raw " Arnd Bergmann
2019-04-16 20:28 ` [PATCH v3 26/26] compat_ioctl: remove last RAID handling code Arnd Bergmann
2019-04-17 8:05 ` [PATCH v3 20/26] compat_ioctl: remove translation for sound ioctls Takashi Iwai
2019-04-29 7:05 ` Takashi Iwai
2019-04-29 12:43 ` Arnd Bergmann
2019-04-16 22:33 ` [PATCH v3 00/26] compat_ioctl: cleanups Douglas Gilbert
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