Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH] time: copy tai value (International Atomic Time, in seconds) to output __user struct in get_old_timex32(). | Date | Thu, 01 Dec 2022 13:41:56 +0100 |
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On Wed, Nov 23 2022 at 20:53, Arnd Bergmann wrote: > On Wed, Nov 23, 2022, at 19:54, John Stultz wrote: >>> --- a/kernel/time/time.c >>> +++ b/kernel/time/time.c >>> @@ -311,6 +311,7 @@ int get_old_timex32(struct __kernel_timex *txc, const struct old_timex32 __user >>> txc->calcnt = tx32.calcnt; >>> txc->errcnt = tx32.errcnt; >>> txc->stbcnt = tx32.stbcnt; >>> + txc->tai = tx32.tai; >>> >> >> This does seem like something that was overlooked. >> >> Arnd: There isn't something more subtle I'm missing here, right? > > I agree. Looking at the git history, it seems that the tai field > was added a long time ago in 153b5d054ac2 ("ntp: support for TAI"). > The commit correctly did the conversion for copying the data out > of the kernel and did not copy the value in because it wasn't > needed at the time. > > I don't see any user of the tai field that gets copied into > the kernel, so the bug appears harmless, but Jacob's fix is > nevertheless correct, as we should not use any uninitialized > data in a structure that comes from userspace.
There is no uninitialized data. txc is zeroed at the beginning of that function.
I agree that it's inconsistent vs. the regular adjtimex(), but as there is no usage of the txc->tai value coming from user space it's pretty much cosmetic.
Thanks,
tglx
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