| Date | Thu, 10 Jul 2014 23:48:45 +0400 | Subject | Re: [RFC/PATCH RESEND -next 01/21] Add kernel address sanitizer infrastructure. | From | Andrey Ryabinin <> |
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2014-07-10 19:55 GMT+04:00 Dave Hansen <dave.hansen@intel.com>: > On 07/10/2014 05:12 AM, Andrey Ryabinin wrote: >> On 07/10/14 00:26, Dave Hansen wrote: >>> On 07/09/2014 04:29 AM, Andrey Ryabinin wrote: >>>> Address sanitizer dedicates 1/8 of the low memory to the shadow memory and uses direct >>>> mapping with a scale and offset to translate a memory address to its corresponding >>>> shadow address. >>>> >>>> Here is function to translate address to corresponding shadow address: >>>> >>>> unsigned long kasan_mem_to_shadow(unsigned long addr) >>>> { >>>> return ((addr - PAGE_OFFSET) >> KASAN_SHADOW_SCALE_SHIFT) >>>> + kasan_shadow_start; >>>> } >>> >>> How does this interact with vmalloc() addresses or those from a kmap()? >>> >> It's used only for lowmem: >> >> static inline bool addr_is_in_mem(unsigned long addr) >> { >> return likely(addr >= PAGE_OFFSET && addr < (unsigned long)high_memory); >> } > > That's fine, and definitely covers the common cases. Could you make > sure to call this out explicitly? Also, there's nothing to _keep_ this > approach working for things out of the direct map, right? It would just > be a matter of updating the shadow memory to have entries for the other > virtual address ranges.
Why do you want shadow for things out of the direct map? If you want to catch use-after-free in vmalloc than DEBUG_PAGEALLOC will be enough. If you want catch out-of-bounds in vmalloc you don't need anything, because vmalloc allocates guarding hole in the end. Or do you want something else?
> > addr_is_in_mem() is a pretty bad name for what it's doing. :) > > I'd probably call it something like kasan_tracks_vaddr(). > Agree
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-- Best regards, Andrey Ryabinin
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