Messages in this thread | | | Subject | Re: [PATCH 5.2 36/37] vhost: block speculation of translated descriptors | From | Thomas Backlund <> | Date | Sun, 15 Sep 2019 12:34:57 +0300 |
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Den 14-09-2019 kl. 11:08, skrev Greg Kroah-Hartman: > On Sat, Sep 14, 2019 at 09:15:48AM +0200, Stefan Lippers-Hollmann wrote: >> Hi >> >> On 2019-09-14, Greg Kroah-Hartman wrote: >>> On Sat, Sep 14, 2019 at 02:54:11AM +0200, Stefan Lippers-Hollmann wrote: >>>> On 2019-09-13, Greg Kroah-Hartman wrote: >>>>> From: Michael S. Tsirkin <mst@redhat.com> >>>>> >>>>> commit a89db445fbd7f1f8457b03759aa7343fa530ef6b upstream. >>>>> >>>>> iovec addresses coming from vhost are assumed to be >>>>> pre-validated, but in fact can be speculated to a value >>>>> out of range. >>>>> >>>>> Userspace address are later validated with array_index_nospec so we can >>>>> be sure kernel info does not leak through these addresses, but vhost >>>>> must also not leak userspace info outside the allowed memory table to >>>>> guests. >>>>> >>>>> Following the defence in depth principle, make sure >>>>> the address is not validated out of node range. >> [...] >>> Do you have the same problem with Linus's tree right now? >> >> Actually, yes I do (I had not tested i386 for 5.3~ within the last ~2 >> weeks, only amd64). Very similar kernel config, same compiler versions >> but built in a slightly different environment (built directly on the bare >> iron, in a amd64 multilib userspace, rather than a pure-i386 chroot on an >> amd64 kernel). >> >> $ git describe >> v5.3-rc8-36-ga7f89616b737 >> >> $ LANG= make ARCH=x86 -j1 bzImage modules >> CALL scripts/checksyscalls.sh >> CALL scripts/atomic/check-atomics.sh >> CHK include/generated/compile.h >> CHK kernel/kheaders_data.tar.xz >> CC [M] drivers/vhost/vhost.o >> In file included from ./include/linux/export.h:45, >> from ./include/linux/linkage.h:7, >> from ./include/linux/kernel.h:8, >> from ./include/linux/list.h:9, >> from ./include/linux/wait.h:7, >> from ./include/linux/eventfd.h:13, >> from drivers/vhost/vhost.c:13: >> drivers/vhost/vhost.c: In function 'translate_desc': >> ./include/linux/compiler.h:350:38: error: call to '__compiletime_assert_2076' declared with attribute error: BUILD_BUG_ON failed: sizeof(_s) > sizeof(long) >> 350 | _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) >> | ^ >> ./include/linux/compiler.h:331:4: note: in definition of macro '__compiletime_assert' >> 331 | prefix ## suffix(); \ >> | ^~~~~~ >> ./include/linux/compiler.h:350:2: note: in expansion of macro '_compiletime_assert' >> 350 | _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) >> | ^~~~~~~~~~~~~~~~~~~ >> ./include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert' >> 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) >> | ^~~~~~~~~~~~~~~~~~ >> ./include/linux/build_bug.h:50:2: note: in expansion of macro 'BUILD_BUG_ON_MSG' >> 50 | BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) >> | ^~~~~~~~~~~~~~~~ >> ./include/linux/nospec.h:56:2: note: in expansion of macro 'BUILD_BUG_ON' >> 56 | BUILD_BUG_ON(sizeof(_s) > sizeof(long)); \ >> | ^~~~~~~~~~~~ >> drivers/vhost/vhost.c:2076:5: note: in expansion of macro 'array_index_nospec' >> 2076 | array_index_nospec((unsigned long)(addr - node->start), >> | ^~~~~~~~~~~~~~~~~~ >> make[2]: *** [scripts/Makefile.build:281: drivers/vhost/vhost.o] Error 1 >> make[1]: *** [scripts/Makefile.build:497: drivers/vhost] Error 2 >> make: *** [Makefile:1083: drivers] Error 2 >> >> $ git revert a89db445fbd7f1f8457b03759aa7343fa530ef6b >> >> $ LANG= make ARCH=x86 -j16 bzImage modules >> CALL scripts/atomic/check-atomics.sh >> CALL scripts/checksyscalls.sh >> CHK include/generated/compile.h >> CHK kernel/kheaders_data.tar.xz >> Building modules, stage 2. >> Kernel: arch/x86/boot/bzImage is ready (#1) >> MODPOST 3464 modules >> >> $ echo $? >> 0 >> >> $ find . -name vhost\\.ko >> ./drivers/vhost/vhost.ko >> >> I've attached the affected kernel config for v5.3~/ i386. > > Ok, good, we will be "bug compatible" at the very least now :) > > When this gets fixed in Linus's tree we can backport the fix here as > well. The number of users of that compiler version/configuration is > probably pretty low at the moment to want to hold off on this fix. >
This is now reverted upstream:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0d4a3f2abbef73b9e5bb5f12213c275565473588
-- Thomas
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