2021-04-12 12:53:07

by Chen Jun

Subject: [PATCH] time: Fix overwrite err unexpected in clock_adjtime32

the correct error is covered by put_old_timex32.

Fixes: f1f1d5ebd10f ("posix-timers: Introduce a syscall for clock tuning.")
Signed-off-by: Chen Jun <[email protected]>
---
kernel/time/posix-timers.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index bf540f5a..dd5697d 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -1191,8 +1191,8 @@ SYSCALL_DEFINE2(clock_adjtime32, clockid_t, which_clock,

err = do_clock_adjtime(which_clock, &ktx);

- if (err >= 0)
- err = put_old_timex32(utp, &ktx);
+ if (err >= 0 && put_old_timex32(utp, &ktx))
+ return -EFAULT;

return err;
}
--
2.9.4

2021-04-12 14:21:28

by Richard Cochran

Subject: Re: [PATCH] time: Fix overwrite err unexpected in clock_adjtime32

On Mon, Apr 12, 2021 at 12:45:51PM +0000, Chen Jun wrote:
> the correct error is covered by put_old_timex32.

Well, the non-negative return code (TIME_OK, TIME_INS, etc) is
clobbered by put_old_timex32().

> Fixes: f1f1d5ebd10f ("posix-timers: Introduce a syscall for clock tuning.")

This is not the correct commit for the "Fixes" tag. Please find the
actual commit that introduced the issue.

In commit f1f1d5ebd10f the code looked like this...

long compat_sys_clock_adjtime(clockid_t which_clock,
struct compat_timex __user *utp)
{
struct timex txc;
mm_segment_t oldfs;
int err, ret;

err = compat_get_timex(&txc, utp);
if (err)
return err;

oldfs = get_fs();
set_fs(KERNEL_DS);
ret = sys_clock_adjtime(which_clock, (struct timex __user *) &txc);
set_fs(oldfs);

err = compat_put_timex(utp, &txc);
if (err)
return err;

return ret;
}

Thanks,
Richard



> Signed-off-by: Chen Jun <[email protected]>
> ---
> kernel/time/posix-timers.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
> index bf540f5a..dd5697d 100644
> --- a/kernel/time/posix-timers.c
> +++ b/kernel/time/posix-timers.c
> @@ -1191,8 +1191,8 @@ SYSCALL_DEFINE2(clock_adjtime32, clockid_t, which_clock,
>
> err = do_clock_adjtime(which_clock, &ktx);
>
> - if (err >= 0)
> - err = put_old_timex32(utp, &ktx);
> + if (err >= 0 && put_old_timex32(utp, &ktx))
> + return -EFAULT;
>
> return err;
> }
> --
> 2.9.4
>

2021-04-12 14:54:49

by Chen Jun

Subject: Re: [PATCH] time: Fix overwrite err unexpected in clock_adjtime32

$B:_(B 2021/4/12 22:20, Richard Cochran $B<LF;(B:
> On Mon, Apr 12, 2021 at 12:45:51PM +0000, Chen Jun wrote:
>> the correct error is covered by put_old_timex32.
>
> Well, the non-negative return code (TIME_OK, TIME_INS, etc) is
> clobbered by put_old_timex32().
>
>> Fixes: f1f1d5ebd10f ("posix-timers: Introduce a syscall for clock tuning.")
>
> This is not the correct commit for the "Fixes" tag. Please find the
> actual commit that introduced the issue.
>
> In commit f1f1d5ebd10f the code looked like this...
>
> long compat_sys_clock_adjtime(clockid_t which_clock,
> struct compat_timex __user *utp)
> {
> struct timex txc;
> mm_segment_t oldfs;
> int err, ret;
>
> err = compat_get_timex(&txc, utp);
> if (err)
> return err;
>
> oldfs = get_fs();
> set_fs(KERNEL_DS);
> ret = sys_clock_adjtime(which_clock, (struct timex __user *) &txc);
> set_fs(oldfs);
>
> err = compat_put_timex(utp, &txc);
> if (err)
> return err;
>
> return ret;
> }
>

f1f1d5ebd10:
Introduce compat_sys_clock_adjtime

62a6fa97684:
rename compat_sys_clock_adjtime to COMPAT_SYSCALL_DEFINE2(clock_adjtime

3a4d44b6162:
move COMPAT_SYSCALL_DEFINE2(clock_adjtime from kernel/compat.c to
kernel/time/posix-timers.c

8dabe7245bb:
COMPAT_SYSCALL_DEFINE2(clock_adjtime, ..
-> SYSCALL_DEFINE2(clock_adjtime32, ..

The implement of clock_adjtime32 is similar to compat_sys_clock_adjtime.
And I think f1f1d5ebd10 introduced the problem actually.

> Thanks,
> Richard
>
>
>
>> Signed-off-by: Chen Jun <[email protected]>
>> ---
>> kernel/time/posix-timers.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
>> index bf540f5a..dd5697d 100644
>> --- a/kernel/time/posix-timers.c
>> +++ b/kernel/time/posix-timers.c
>> @@ -1191,8 +1191,8 @@ SYSCALL_DEFINE2(clock_adjtime32, clockid_t, which_clock,
>>
>> err = do_clock_adjtime(which_clock, &ktx);
>>
>> - if (err >= 0)
>> - err = put_old_timex32(utp, &ktx);
>> + if (err >= 0 && put_old_timex32(utp, &ktx))
>> + return -EFAULT;
>>
>> return err;
>> }
>> --
>> 2.9.4
>>
>


--
Regards
Chen Jun

2021-04-12 16:00:27

by Richard Cochran

Subject: Re: [PATCH] time: Fix overwrite err unexpected in clock_adjtime32

On Mon, Apr 12, 2021 at 02:52:11PM +0000, chenjun (AM) wrote:
> 在 2021/4/12 22:20, Richard Cochran 写道:
> > On Mon, Apr 12, 2021 at 12:45:51PM +0000, Chen Jun wrote:
> >> the correct error is covered by put_old_timex32.
> >
> > Well, the non-negative return code (TIME_OK, TIME_INS, etc) is
> > clobbered by put_old_timex32().
> >
> >> Fixes: f1f1d5ebd10f ("posix-timers: Introduce a syscall for clock tuning.")
> >
> > This is not the correct commit for the "Fixes" tag. Please find the
> > actual commit that introduced the issue.
> >
> > In commit f1f1d5ebd10f the code looked like this...
> >
> > long compat_sys_clock_adjtime(clockid_t which_clock,
> > struct compat_timex __user *utp)
> > {
> > struct timex txc;
> > mm_segment_t oldfs;
> > int err, ret;
> >
> > err = compat_get_timex(&txc, utp);
> > if (err)
> > return err;
> >
> > oldfs = get_fs();
> > set_fs(KERNEL_DS);
> > ret = sys_clock_adjtime(which_clock, (struct timex __user *) &txc);
> > set_fs(oldfs);
> >
> > err = compat_put_timex(utp, &txc);
> > if (err)
> > return err;
> >
> > return ret;
> > }

Look at the code ^^^

> The implement of clock_adjtime32 is similar to compat_sys_clock_adjtime.
> And I think f1f1d5ebd10 introduced the problem actually.

See how 'ret' and 'err' are two separate variables? It makes a difference.

Thanks,
Richard

2021-04-13 07:44:06

by Chen Jun

Subject: Re: [PATCH] time: Fix overwrite err unexpected in clock_adjtime32

$B:_(B 2021/4/12 23:58, Richard Cochran $B<LF;(B:
> On Mon, Apr 12, 2021 at 02:52:11PM +0000, chenjun (AM) wrote:
>> $B:_(B 2021/4/12 22:20, Richard Cochran $B<LF;(B:
>>> On Mon, Apr 12, 2021 at 12:45:51PM +0000, Chen Jun wrote:
>>>> the correct error is covered by put_old_timex32.
>>>
>>> Well, the non-negative return code (TIME_OK, TIME_INS, etc) is
>>> clobbered by put_old_timex32().
>>>
>>>> Fixes: f1f1d5ebd10f ("posix-timers: Introduce a syscall for clock tuning.")
>>>
>>> This is not the correct commit for the "Fixes" tag. Please find the
>>> actual commit that introduced the issue.
>>>
>>> In commit f1f1d5ebd10f the code looked like this...
>>>
>>> long compat_sys_clock_adjtime(clockid_t which_clock,
>>> struct compat_timex __user *utp)
>>> {
>>> struct timex txc;
>>> mm_segment_t oldfs;
>>> int err, ret;
>>>
>>> err = compat_get_timex(&txc, utp);
>>> if (err)
>>> return err;
>>>
>>> oldfs = get_fs();
>>> set_fs(KERNEL_DS);
>>> ret = sys_clock_adjtime(which_clock, (struct timex __user *) &txc);
>>> set_fs(oldfs);
>>>
>>> err = compat_put_timex(utp, &txc);
>>> if (err)
>>> return err;
>>>
>>> return ret;
>>> }
>
> Look at the code ^^^
>
>> The implement of clock_adjtime32 is similar to compat_sys_clock_adjtime.
>> And I think f1f1d5ebd10 introduced the problem actually.
>
> See how 'ret' and 'err' are two separate variables? It makes a difference.
>
> Thanks,
> Richard
>

Oh, yee.. Very thanks.

3a4d44b616 ("ntp: Move adjtimex related compat syscalls to native
counterparts") made the change.

--
Regards
Chen Jun