On Tue, Feb 13, 2018 at 11:56:47AM -0500, Dennis Dalessandro wrote:
> On 2/13/2018 5:18 AM, Leon Romanovsky wrote:
> >From: Matan Barak <matanb@xxxxxxxxxxxx>
> >
> >32 bit processes running on a 64 bit kernel call compat_ioctl so that
> >implementations can revise any structure layout issues. Point compat_ioctl
> >at our normal ioctl because:
> >
> >- All our structures are designed to be the same on 32 and 64 bit, ie we
> > use __aligned_u64 when required and are careful to manage padding.
> >
> >- Any pointers are stored in u64's and userspace is expected
> > to prepare them properly.
> >
> >Signed-off-by: Matan Barak <matanb@xxxxxxxxxxxx>
> >Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
> >Signed-off-by: Leon Romanovsky <leon@xxxxxxxxxx>
> > drivers/infiniband/core/uverbs_main.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> >diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
> >index 395a3b091229..cd72555ad457 100644
> >+++ b/drivers/infiniband/core/uverbs_main.c
> >@@ -942,6 +942,7 @@ static const struct file_operations uverbs_fops = {
> > .llseek = no_llseek,
> > #if IS_ENABLED(CONFIG_INFINIBAND_EXP_USER_ACCESS)
> > .unlocked_ioctl = ib_uverbs_ioctl,
> >+ .compat_ioctl = ib_uverbs_ioctl,
> > #endif
> > };
> >@@ -954,6 +955,7 @@ static const struct file_operations uverbs_mmap_fops = {
> > .llseek = no_llseek,
> > #if IS_ENABLED(CONFIG_INFINIBAND_EXP_USER_ACCESS)
> > .unlocked_ioctl = ib_uverbs_ioctl,
> >+ .compat_ioctl = ib_uverbs_ioctl,
> > #endif
> > };
> >
>
> Is this patch really necessary?
Yes. Without it 32 bit gets:
ioctl(3, _IOC(_IOC_READ|_IOC_WRITE, 0x1b, 0x1, 0x10), 0xffcaf5f8) = -1 ENOTTY (Inappropriate ioctl for device)
> Doesn't sys_ioctl() just end up calling unlocked_ioctl() if
> .compat_ioctl is not set? I guess nothing wrong with being explicit
> here, but this is just a clean-up then, and not an -rc patch.
No, the control flow is really tortured in compat_ioctl.c, but it
will only call compat_ioctl for our case.
Jason
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