Shifting signed 32-bit value by 31 bits is undefined, so we fix it
with the BIT() macro, at the same time, we change the input to
unsigned, and replace "/ 32" with ">> 5".
The UBSAN warning calltrace like below:
UBSAN: shift-out-of-bounds in arch/x86/kvm/reverse_cpuid.h:101:11
left shift of 1 by 31 places cannot be represented in type 'int'
Call Trace:
<TASK>
dump_stack_lvl+0x7d/0xa5
dump_stack+0x15/0x1b
ubsan_epilogue+0xe/0x4e
__ubsan_handle_shift_out_of_bounds+0x1e7/0x20c
kvm_set_cpu_caps+0x15a/0x770 [kvm]
hardware_setup+0xa6f/0xdfe [kvm_intel]
kvm_arch_hardware_setup+0x100/0x1e80 [kvm]
kvm_init+0xdb/0x560 [kvm]
vmx_init+0x161/0x2b4 [kvm_intel]
do_one_initcall+0x76/0x430
do_init_module+0x61/0x28a
load_module+0x1f82/0x2e50
__do_sys_finit_module+0xf8/0x190
__x64_sys_finit_module+0x23/0x30
do_syscall_64+0x58/0x80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
</TASK>
Fixes: a7c48c3f56db ("KVM: x86: Expand build-time assertion on reverse CPUID usage")
Signed-off-by: Gaosheng Cui <cuigaosheng1@xxxxxxxxxx>
---
v2:
- Fix the issue by the BIT() macro, change the input to unsigned and
- replace "/ 32" with ">> 5", update the commit msg as well, Thanks!
arch/x86/kvm/reverse_cpuid.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
index a19d473d0184..f1680344de56 100644
--- a/arch/x86/kvm/reverse_cpuid.h
+++ b/arch/x86/kvm/reverse_cpuid.h
@@ -93,12 +93,12 @@ static __always_inline u32 __feature_leaf(int x86_feature)
* "word" (stored in bits 31:5). The word is used to index into arrays of
* bit masks that hold the per-cpu feature capabilities, e.g. this_cpu_has().
*/
-static __always_inline u32 __feature_bit(int x86_feature)
+static __always_inline u32 __feature_bit(unsigned int x86_feature)
{
x86_feature = __feature_translate(x86_feature);
- reverse_cpuid_check(x86_feature / 32);
- return 1 << (x86_feature & 31);
+ reverse_cpuid_check(x86_feature >> 5);
+ return BIT(x86_feature & 31);
}
#define feature_bit(name) __feature_bit(X86_FEATURE_##name)
--
2.25.1
