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Message-ID: <CA+icZUV0HEF_hwr-eSovntfcT0++FBrQN-HbFL+oZtnKjJzLtA@mail.gmail.com> Date: Sat, 21 Dec 2024 19:25:54 +0100 From: Sedat Dilek <sedat.dilek@...il.com> To: Andrew Cooper <andrew.cooper3@...rix.com> Cc: Juergen Gross <jgross@...e.com>, Peter Zijlstra <peterz@...radead.org>, Sami Tolvanen <samitolvanen@...gle.com>, Jan Beulich <jbeulich@...e.com>, Josh Poimboeuf <jpoimboe@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org, stable@...r.kernel.org, Kees Cook <kees@...nel.org>, Nathan Chancellor <nathan@...nel.org>, llvm@...ts.linux.dev, xen-devel <xen-devel@...ts.xenproject.org> Subject: Re: [Linux-6.12.y] XEN: CVE-2024-53241 / XSA-466 and Clang-kCFI On Sat, Dec 21, 2024 at 7:17 PM Sedat Dilek <sedat.dilek@...il.com> wrote: > > On Fri, Dec 20, 2024 at 2:39 AM Andrew Cooper <andrew.cooper3@...rix.com> wrote: > > > > On 20/12/2024 12:27 am, Sedat Dilek wrote: > > > On Fri, Dec 20, 2024 at 12:26 AM Andrew Cooper > > > <andrew.cooper3@...rix.com> wrote: > > >> On 19/12/2024 11:10 pm, Sedat Dilek wrote: > > >>> On Thu, Dec 19, 2024 at 6:07 PM Sedat Dilek <sedat.dilek@...il.com> wrote: > > >>>> On Thu, Dec 19, 2024 at 5:44 PM Andrew Cooper <andrew.cooper3@...rix.com> wrote: > > >>>>> On 19/12/2024 4:14 pm, Sedat Dilek wrote: > > >>>>>> Hi, > > >>>>>> > > >>>>>> Linux v6.12.6 will include XEN CVE fixes from mainline. > > >>>>>> > > >>>>>> Here, I use Debian/unstable AMD64 and the SLIM LLVM toolchain 19.1.x > > >>>>>> from kernel.org. > > >>>>>> > > >>>>>> What does it mean in ISSUE DESCRIPTION... > > >>>>>> > > >>>>>> Furthermore, the hypercall page has no provision for Control-flow > > >>>>>> Integrity schemes (e.g. kCFI/CET-IBT/FineIBT), and will simply > > >>>>>> malfunction in such configurations. > > >>>>>> > > >>>>>> ...when someone uses Clang-kCFI? > > >>>>> The hypercall page has functions of the form: > > >>>>> > > >>>>> MOV $x, %eax > > >>>>> VMCALL / VMMCALL / SYSCALL > > >>>>> RET > > >>>>> > > >>>>> There are no ENDBR instructions, and no prologue/epilogue for hash-based > > >>>>> CFI schemes. > > >>>>> > > >>>>> This is because it's code provided by Xen, not code provided by Linux. > > >>>>> > > >>>>> The absence of ENDBR instructions will yield #CP when CET-IBT is active, > > >>>>> and the absence of hash prologue/epilogue lets the function be used in a > > >>>>> type-confused manor that CFI should have caught. > > >>>>> > > >>>>> ~Andrew > > >>>> Thanks for the technical explanation, Andrew. > > >>>> > > >>>> Hope that helps the folks of "CLANG CONTROL FLOW INTEGRITY SUPPORT". > > >>>> > > >>>> I am not an active user of XEN in the Linux-kernel but I am willing to > > >>>> test when Linux v6.12.6 is officially released and give feedback. > > >>>> > > >>> https://wiki.xenproject.org/wiki/Testing_Xen#Presence_test > > >>> https://wiki.xenproject.org/wiki/Testing_Xen#Commands_for_presence_testing > > >>> > > >>> # apt install -t unstable xen-utils-4.17 -y > > >>> > > >>> # xl list > > >>> Name ID Mem VCPUs State Time(s) > > >>> Domain-0 0 7872 4 r----- 398.2 > > >>> > > >>> Some basic tests LGTM - see also attached stuff. > > >>> > > >>> If you have any tests to recommend, let me know. > > >> That itself is good enough as a smoke test. Thankyou for trying it out. > > >> > > >> If you want something a bit more thorough, try > > >> https://xenbits.xen.org/docs/xtf/ (Xen's self-tests) > > >> > > >> Grab and build it, and `./xtf-runner -aqq --host` will run a variety of > > >> extra codepaths in dom0, without the effort of making/running full guests. > > >> > > >> ~Andrew > > > Run on Debian 6.12.5 and my selfmade 6.12.5 and 6.12.6. > > > All tests lead to a reboot in case of Debian or in my kernels to a shutdown. > > > > > > Can you recommend a specific test? > > > > Oh, that's distinctly less good. > > > > Start with just "example". It's literally a hello world microkernel, > > but the symptoms you're seeing is a dom0 crash, so it will likely > > provoke it. > > > > Do you have serial to the machine? If so, boot Xen with `console=com1 > > com1=115200,8n1` (or com2, as appropriate). > > > > If not and you've only got a regular screen, boot Xen with `vga=,keep > > noreboot` (comma is important) which might leave enough information on > > screen to get an idea of what's going on. > > > > YES > > # xl info | grep xen_commandline > xen_commandline : placeholder vga=,keep noreboot > > > Full command line docs at > > https://xenbits.xen.org/docs/unstable/misc/xen-command-line.html > > > > > dileks@...za:~/src/xtf/git$ sudo ./xtf-runner --list functional xsa | grep xsa-4 > > > test-pv64-xsa-444 > > > test-hvm64-xsa-451 > > > test-hvm64-xsa-454 > > > > > > Is there no xsa-466 test? > > > > No. XSA-466 is really "well don't do that then if it matters". > > > > More generally, not all XSAs are amenable to testing in this way. > > > > ~Andrew > > On Debian 6.12.6 kernel the TESTS stop with test-hvm64-xsa-454 - > machine freezes - hard reboot. > > dileks@...za:~/src/xtf/git$ sudo ./xtf-runner -a --host > > root@...za:/var/log/xen# LC_ALL=C ls -alth | head -20 > total 1.7M > -rw-r--r-- 1 root adm 1008K Dec 21 19:10 xenstored-access.log > drwxr-xr-x 16 root root 4.0K Dec 21 18:59 .. > -rw-r--r-- 1 root adm 32 Dec 21 18:58 xenstored.log > drwxr-s--- 2 root adm 36K Dec 21 18:58 . > -rw-r--r-- 1 root adm 229 Dec 21 18:53 xl-test-hvm64-xsa-317.log > -rw-r--r-- 1 root adm 67 Dec 21 18:53 xl-test-hvm64-xsa-454.log > -rw-r--r-- 1 root adm 145 Dec 21 18:53 qemu-dm-test-hvm64-xsa-454.log > -rw-r--r-- 1 root adm 232 Dec 21 18:53 qemu-dm-test-hvm64-xsa-451.log > -rw-r--r-- 1 root adm 211 Dec 21 18:53 xl-test-hvm64-xsa-451.log > -rw-r--r-- 1 root adm 232 Dec 21 18:53 xl-test-hvm32pse-xsa-317.log > -rw-r--r-- 1 root adm 228 Dec 21 18:53 xl-test-pv64-xsa-444.log > -rw-r--r-- 1 root adm 228 Dec 21 18:53 xl-test-pv64-xsa-339.log > -rw-r--r-- 1 root adm 228 Dec 21 18:53 xl-test-pv64-xsa-333.log > -rw-r--r-- 1 root adm 228 Dec 21 18:53 xl-test-pv64-xsa-317.log > -rw-r--r-- 1 root adm 232 Dec 21 18:53 qemu-dm-test-hvm64-xsa-317.log > -rw-r--r-- 1 root adm 232 Dec 21 18:53 xl-test-hvm32pae-xsa-317.log > -rw-r--r-- 1 root adm 232 Dec 21 18:53 qemu-dm-test-hvm32pse-xsa-317.log > -rw-r--r-- 1 root adm 229 Dec 21 18:53 xl-test-hvm32-xsa-317.log > -rw-r--r-- 1 root adm 232 Dec 21 18:53 qemu-dm-test-hvm32pae-xsa-317.log > > root@...za:/var/log/xen# cat qemu-dm-test-hvm64-xsa-454.log > VNC server running on 127.0.0.1:5900 > xen-qemu-system-i386: failed to create 'console' device '0': declining to handle > console type 'xenconsoled' > > root@...za:/var/log/xen# cat xl-test-hvm64-xsa-454.log > Waiting for domain test-hvm64-xsa-454 (domid 94) to die [pid 4686] > > -Sedat- With... dileks@...za:~/src/xtf/git$ mv tests/xsa-454 ../ dileks@...za:~/src/xtf/git$ mv tests/xsa-consoleio-write ../ Combined test results: test-hvm32-cpuid-faulting SKIP test-hvm32pae-cpuid-faulting SKIP test-hvm32pse-cpuid-faulting SKIP test-hvm64-cpuid-faulting SKIP test-pv64-cpuid-faulting SKIP test-hvm64-fpu-exception-emulation SKIP test-hvm32-invlpg~hap SUCCESS test-hvm32-invlpg~shadow SUCCESS test-hvm32pae-invlpg~hap SUCCESS test-hvm32pae-invlpg~shadow SUCCESS test-hvm64-invlpg~hap SUCCESS test-hvm64-invlpg~shadow SUCCESS test-hvm64-lbr-tsx-vmentry SUCCESS test-hvm32-livepatch-priv-check SUCCESS test-hvm64-livepatch-priv-check SUCCESS test-pv64-livepatch-priv-check SUCCESS test-hvm32-lm-ts SUCCESS test-hvm64-lm-ts SUCCESS test-hvm32pae-memop-seg SUCCESS test-hvm64-memop-seg SUCCESS test-pv64-memop-seg SUCCESS test-hvm32pae-nmi-taskswitch-priv SUCCESS test-pv64-pv-fsgsbase SKIP test-pv64-pv-iopl~hypercall SUCCESS test-pv64-pv-iopl~vmassist SUCCESS test-hvm32-swint-emulation SKIP test-hvm32pae-swint-emulation SKIP test-hvm32pse-swint-emulation SKIP test-hvm64-swint-emulation SKIP test-hvm32-umip SKIP test-hvm64-umip SKIP test-hvm32-xsa-122 SUCCESS test-hvm32pae-xsa-122 SUCCESS test-hvm32pse-xsa-122 SUCCESS test-hvm64-xsa-122 SUCCESS test-pv64-xsa-122 SUCCESS test-hvm32-xsa-123 SKIP test-pv64-xsa-167 SKIP test-hvm64-xsa-168~shadow SUCCESS test-hvm64-xsa-170 SKIP test-hvm64-xsa-173~shadow SUCCESS test-pv64-xsa-182 SUCCESS test-hvm32-xsa-186 SKIP test-hvm64-xsa-186 SKIP test-hvm32-xsa-188 SUCCESS test-hvm32pae-xsa-188 SUCCESS test-hvm32pse-xsa-188 SUCCESS test-hvm64-xsa-188 SUCCESS test-pv64-xsa-188 SUCCESS test-hvm32-xsa-191 SKIP test-hvm32-xsa-192 SUCCESS test-pv64-xsa-193 SUCCESS test-hvm64-xsa-195 SUCCESS test-hvm64-xsa-196 SKIP test-hvm32-xsa-200 SKIP test-hvm32-xsa-203 SKIP test-hvm64-xsa-204 SKIP test-pv64-xsa-212 SUCCESS test-pv64-xsa-213 SUCCESS test-hvm64-xsa-221 SUCCESS test-pv64-xsa-221 SUCCESS test-pv64-xsa-224 SUCCESS test-pv64-xsa-227 SUCCESS test-hvm64-xsa-231 SUCCESS test-pv64-xsa-231 SUCCESS test-hvm64-xsa-232 SUCCESS test-pv64-xsa-232 SUCCESS test-pv64-xsa-234 SUCCESS test-hvm32-xsa-239 SUCCESS test-pv64-xsa-255 SUCCESS test-pv64-xsa-259 SUCCESS test-pv64-xsa-260 SUCCESS test-hvm64-xsa-261 SUCCESS test-pv64-xsa-265 SUCCESS test-hvm64-xsa-269 SUCCESS test-hvm64-xsa-277 SUCCESS test-hvm64-xsa-278 SUCCESS test-pv64-xsa-279 SUCCESS test-pv64-xsa-286 SUCCESS test-pv64-xsa-296 SUCCESS test-pv64-xsa-298 SUCCESS test-hvm64-xsa-304 SUCCESS test-hvm64-xsa-308 SUCCESS test-pv64-xsa-316 SUCCESS test-hvm32-xsa-317 SUCCESS test-hvm32pae-xsa-317 SUCCESS test-hvm32pse-xsa-317 SUCCESS test-hvm64-xsa-317 SUCCESS test-pv64-xsa-317 SUCCESS test-pv64-xsa-333 SUCCESS test-pv64-xsa-339 SUCCESS test-pv64-xsa-444 SKIP test-hvm64-xsa-451 SKIP -Sedat-
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