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| author |   Chang S. Bae <chang.seok.bae@intel.com> | 2022-10-21 11:58:44 -0700 |
|---|---|---|
| committer |   Dave Hansen <dave.hansen@linux.intel.com> | 2022-10-21 15:22:09 -0700 |
| commit | 471f0aa7fa64e23766a1473b32d9ec3f0718895a (patch) | |
| tree | 37504e30417860e46ef62ef5f9eab77b3588e386 /arch/x86/kernel | |
| parent | perf/x86/intel/lbr: Use setup_clear_cpu_cap() instead of clear_cpu_cap() (diff) | |
| download | linux-dev-471f0aa7fa64e23766a1473b32d9ec3f0718895a.tar.xz linux-dev-471f0aa7fa64e23766a1473b32d9ec3f0718895a.zip | |
x86/fpu: Fix copy_xstate_to_uabi() to copy init states correctly
When an extended state component is not present in fpstate, but in init
state, the function copies from init_fpstate via copy_feature().
But, dynamic states are not present in init_fpstate because of all-zeros
init states. Then retrieving them from init_fpstate will explode like this:
BUG: kernel NULL pointer dereference, address: 0000000000000000
...
RIP: 0010:memcpy_erms+0x6/0x10
? __copy_xstate_to_uabi_buf+0x381/0x870
fpu_copy_guest_fpstate_to_uabi+0x28/0x80
kvm_arch_vcpu_ioctl+0x14c/0x1460 [kvm]
? __this_cpu_preempt_check+0x13/0x20
? vmx_vcpu_put+0x2e/0x260 [kvm_intel]
kvm_vcpu_ioctl+0xea/0x6b0 [kvm]
? kvm_vcpu_ioctl+0xea/0x6b0 [kvm]
? __fget_light+0xd4/0x130
__x64_sys_ioctl+0xe3/0x910
? debug_smp_processor_id+0x17/0x20
? fpregs_assert_state_consistent+0x27/0x50
do_syscall_64+0x3f/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd
Adjust the 'mask' to zero out the userspace buffer for the features that
are not available both from fpstate and from init_fpstate.
The dynamic features depend on the compacted XSAVE format. Ensure it is
enabled before reading XCOMP_BV in init_fpstate.
Fixes: 2308ee57d93d ("x86/fpu/amx: Enable the AMX feature in 64-bit mode")
Reported-by: Yuan Yao <yuan.yao@intel.com>
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Tested-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/lkml/BYAPR11MB3717EDEF2351C958F2C86EED95259@BYAPR11MB3717.namprd11.prod.outlook.com/
Link: https://lkml.kernel.org/r/20221021185844.13472-1-chang.seok.bae@intel.com
Diffstat (limited to 'arch/x86/kernel')
| -rw-r--r-- | arch/x86/kernel/fpu/xstate.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index e77cabfa802f..59e543b95a3c 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -1125,6 +1125,15 @@ void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate, */ mask = fpstate->user_xfeatures; + /* + * Dynamic features are not present in init_fpstate. When they are + * in an all zeros init state, remove those from 'mask' to zero + * those features in the user buffer instead of retrieving them + * from init_fpstate. + */ + if (fpu_state_size_dynamic()) + mask &= (header.xfeatures | xinit->header.xcomp_bv); + for_each_extended_xfeature(i, mask) { /* * If there was a feature or alignment gap, zero the space |