Messages in this thread | | | Date | Sun, 1 Jan 2023 06:55:42 +0200 | Subject | Re: [PATCH qemu] x86: don't let decompressed kernel image clobber setup_data | From | Mika Penttilä <> |
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On 1.1.2023 6.33, H. Peter Anvin wrote: > > > On 12/31/22 10:22, Jason A. Donenfeld wrote: >> On Sat, Dec 31, 2022 at 03:24:32PM +0100, Borislav Petkov wrote: >>> On Sat, Dec 31, 2022 at 02:51:28PM +0100, Jason A. Donenfeld wrote: >>>> That failure is unrelated to the ident mapping issue Peter and >>>> I discussed. The original failure is described in the commit message: >>>> decompression clobbers the data, so sd->next points to garbage. >>> >>> Right >> >> So with that understanding confirmed, I'm confused at your surprise that >> hpa's unrelated fix to the different issue didn't fix this issue. >> > > If decompression does clobber the data, then we *also* need to figure > out why that is. There are basically three possibilities: > > 1. If physical KASLR is NOT used: > > a. The boot loader doesn't honor the kernel safe area properly; > b. Somewhere in the process a bug in the calculation of the > kernel safe area has crept in. > > 2. If physical KASLR IS used: > > The decompressor doesn't correctly keep track of nor relocate > all the keep-out zones before picking a target address.
Seems setup_data is not included in those mem_avoid regions.
> > One is a bootloader bug, two is a kernel bug. My guess is (2) is the > culprit, but (1b) should be checked, too. > > -hpa >
--Mika
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