Messages in this thread | | | Date | Tue, 1 Sep 2020 09:21:58 -0500 | From | Josh Poimboeuf <> | Subject | Re: [PATCH] x86/uaccess: Use pointer masking to limit uaccess speculation |
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On Tue, Sep 01, 2020 at 03:02:08PM +0100, Mark Rutland wrote: > d instead do user pointer > > masking, throughout the x86 uaccess code. This is similar to what arm64 > > is already doing. > > > > barrier_nospec() is now unused, and can be removed. > > One thing to consider is whether you need a speculation barrier after > set_fs(). Otherwise for code like: > > | fs = get_fs(); > | if (cond) > | set_fs(KERNEL_DS); > | copy_to_user(...) > | set_fs(fs) > > ... the set_fs() can occur speculatively, and may be able to satisfy > the masking logic if forwarded within the cpu. > > See arm64 commit: > > c2f0ad4fc089cff8 ("arm64: uaccess: Prevent speculative use of the current addr_limit")
Do you have any examples of that conditional set_fs(KERNEL_DS) pattern? I wasn't able to find any.
-- Josh
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