Messages in this thread | | | Date | Fri, 30 Jul 2021 03:33:54 +0300 | From | Jarkko Sakkinen <> | Subject | Re: [PATCH v3 1/7] x86/sgx: Provide indication of life-cycle of EPC pages |
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On Wed, Jul 28, 2021 at 03:12:03PM -0700, Dave Hansen wrote: > On 7/28/21 1:46 PM, Tony Luck wrote: > > +++ b/arch/x86/kernel/cpu/sgx/main.c > > @@ -581,7 +581,7 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim) > > for ( ; ; ) { > > page = __sgx_alloc_epc_page(); > > if (!IS_ERR(page)) { > > - page->owner = owner; > > + page->owner = owner ? owner : page; > > break; > > } > > I'm a little worried about this. > > Let's say we get confused about the type of the page and dereference > page->owner. If it's NULL, we get a nice oops. If it's a real, valid > pointer, we get real valid memory back that we can scribble on. > > Wouldn't it be safer to do something like: > > page->owner = owner ? owner : (void *)-1; > > -1 is non-NULL, but also invalid, which makes it harder for us to poke > ourselves in the eye.
Works for me.
/Jarkko
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