Re: KMSAN: uninit-value in snapshot_compat_ioctl

Alexander Potapenko
2020-03-09T11:53:42Z

> > Looks like a KMSAN false positive? As far as I can tell, the memory is being
> > initialized by put_user() called under set_fs(KERNEL_DS).

Why? put_user() doesn't write to kernel memory, instead it copies a
value to the userspace.
That's why KMSAN performs kmsan_check_memory() on it.
It would actually be better if KMSAN printed an kernel-infoleak warning instead.

> Although, it also looks like the problematic code can just be removed, since
> always sizeof(compat_loff_t) == sizeof(loff_t). I'll send a patch to do that...

Thanks!

--
Alexander Potapenko
Software Engineer

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