Messages in this thread | | | Subject | Re: [Y2038] [PATCH 6/8] lp: fix sparc64 LPSETTIMEOUT ioctl | From | Ben Hutchings <> | Date | Wed, 20 Nov 2019 22:10:44 +0000 |
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On Wed, 2019-11-20 at 20:46 +0100, Arnd Bergmann wrote: > On Wed, Nov 20, 2019 at 8:27 PM Ben Hutchings > <ben.hutchings@codethink.co.uk> wrote: > > On Fri, 2019-11-08 at 21:34 +0100, Arnd Bergmann wrote: > > > The layout of struct timeval is different on sparc64 from > > > anything else, and the patch I did long ago failed to take > > > this into account. > > > > > > Change it now to handle sparc64 user space correctly again. > > > > > > Quite likely nobody cares about parallel ports on sparc64, > > > but there is no reason not to fix it. > > > > > > Cc: stable@vger.kernel.org > > > Fixes: 9a450484089d ("lp: support 64-bit time_t user space") > > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > > > --- > > > drivers/char/lp.c | 4 ++++ > > > 1 file changed, 4 insertions(+) > > > > > > diff --git a/drivers/char/lp.c b/drivers/char/lp.c > > > index 7c9269e3477a..bd95aba1f9fe 100644 > > > --- a/drivers/char/lp.c > > > +++ b/drivers/char/lp.c > > > @@ -713,6 +713,10 @@ static int lp_set_timeout64(unsigned int minor, void __user *arg) > > > if (copy_from_user(karg, arg, sizeof(karg))) > > > return -EFAULT; > > > > > > + /* sparc64 suseconds_t is 32-bit only */ > > > + if (IS_ENABLED(CONFIG_SPARC64) && !in_compat_syscall()) > > > + karg[1] >>= 32; > > > + > > > return lp_set_timeout(minor, karg[0], karg[1]); > > > } > > > > > > > It seems like it would make way more sense to use __kernel_old_timeval. > > Right, that would work. I tried to keep the patch small here, changing > it to __kernel_old_timeval would require make it all more complicated > since it would still need to check some conditional to tell the difference > between sparc32 and sparc64.
Right.
> I think this patch (relative to the version I posted) would work the same: > > diff --git a/drivers/char/lp.c b/drivers/char/lp.c > index bd95aba1f9fe..86994421ee97 100644 > --- a/drivers/char/lp.c > +++ b/drivers/char/lp.c > @@ -713,13 +713,19 @@ static int lp_set_timeout64(unsigned int minor, > void __user *arg) > if (copy_from_user(karg, arg, sizeof(karg))) > return -EFAULT; > > - /* sparc64 suseconds_t is 32-bit only */ > - if (IS_ENABLED(CONFIG_SPARC64) && !in_compat_syscall()) > - karg[1] >>= 32; > - > return lp_set_timeout(minor, karg[0], karg[1]); > } > > +static int lp_set_timeout(unsigned int minor, void __user *arg)
That function name is already used! Maybe this should be lp_set_timeout_old()?
> +{ > + __kernel_old_timeval tv; > + > + if (copy_from_user(tv, arg, sizeof(karg))) > + return -EFAULT; > + > + return lp_set_timeout(minor, tv->tv_sec, tv->tv_usec); > +} > + > static long lp_ioctl(struct file *file, unsigned int cmd, > unsigned long arg) > { > @@ -730,11 +736,8 @@ static long lp_ioctl(struct file *file, unsigned int cmd, > mutex_lock(&lp_mutex); > switch (cmd) { > case LPSETTIMEOUT_OLD: > - if (BITS_PER_LONG == 32) { > - ret = lp_set_timeout32(minor, (void __user *)arg); > - break; > - } > - /* fall through - for 64-bit */ > + ret = lp_set_timeout(minor, (void __user *)arg); > + break; > case LPSETTIMEOUT_NEW: > ret = lp_set_timeout64(minor, (void __user *)arg); > break; > > Do you like that better?
Yes. Aside from the duplicate function name, it looks correct and cleaner than the current version.
> One difference here is the handling of > LPSETTIMEOUT_NEW on sparc64, which would continue to use > the 64/64 layout rather than the 64/32/pad layout, but that should > be ok, since sparc64 user space using ppdev (if any exists) > would use LPSETTIMEOUT_OLD, not LPSETTIMEOUT_NEW.
Right, that's a little weird but appears to be consistent with "new" socket timestamps.
> > Then you don't have to explicitly handle the sparc64 oddity. > > > > As it is, this still over-reads from user-space which might result in a > > spurious -EFAULT. > > I think you got this wrong: sparc64 like most architectures naturally > aligns 64-bit members, so 'struct timeval' still uses 16 bytes including > the four padding bytes at the end, it just has the nanoseconds in > a different position from all other big-endian architectures.
Oh of course, yes.
Ben.
-- Ben Hutchings, Software Developer Codethink Ltd https://www.codethink.co.uk/ Dale House, 35 Dale Street Manchester, M1 2HF, United Kingdom
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