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@xxxxxxxxxx> > > > > > > > > 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. thanks, greg k-h
