Commit 0027ff2a authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: VMX: fixes for vmentry_l1d_flush module parameter 



Two bug fixes:

1) missing entries in the l1d_param array; this can cause a host crash
if an access attempts to reach the missing entry. Future-proof the get
function against any overflows as well.  However, the two entries
VMENTER_L1D_FLUSH_EPT_DISABLED and VMENTER_L1D_FLUSH_NOT_REQUIRED must
not be accepted by the parse function, so disable them there.

2) invalid values must be rejected even if the CPU does not have the
bug, so test for them before checking boot_cpu_has(X86_BUG_L1TF)

... and a small refactoring, since the .cmd field is redundant with
the index in the array.

Reported-by: default avatarBandan Das <bsd@redhat.com>
Cc: stable@vger.kernel.org
Fixes: a7b9020b
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 3b4cd0ff

arch/x86/kvm/vmx.c

+16 −10
Original line number Diff line number Diff line
@@ -198,12 +198,14 @@ static enum vmx_l1d_flush_state __read_mostly vmentry_l1d_flush_param = VMENTER_ 


static const struct {

	const char *option;

	enum vmx_l1d_flush_state cmd;

	bool for_parse;

} vmentry_l1d_param[] = {

	{"auto",	VMENTER_L1D_FLUSH_AUTO},

	{"never",	VMENTER_L1D_FLUSH_NEVER},

	{"cond",	VMENTER_L1D_FLUSH_COND},

	{"always",	VMENTER_L1D_FLUSH_ALWAYS},

	[VMENTER_L1D_FLUSH_AUTO]	 = {"auto", true},

	[VMENTER_L1D_FLUSH_NEVER]	 = {"never", true},

	[VMENTER_L1D_FLUSH_COND]	 = {"cond", true},

	[VMENTER_L1D_FLUSH_ALWAYS]	 = {"always", true},

	[VMENTER_L1D_FLUSH_EPT_DISABLED] = {"EPT disabled", false},

	[VMENTER_L1D_FLUSH_NOT_REQUIRED] = {"not required", false},

};



#define L1D_CACHE_ORDER 4
@@ -287,8 +289,9 @@ static int vmentry_l1d_flush_parse(const char *s) 


	if (s) {

		for (i = 0; i < ARRAY_SIZE(vmentry_l1d_param); i++) {

			if (sysfs_streq(s, vmentry_l1d_param[i].option))

				return vmentry_l1d_param[i].cmd;

			if (vmentry_l1d_param[i].for_parse &&

			    sysfs_streq(s, vmentry_l1d_param[i].option))

				return i;

		}

	}

	return -EINVAL;
@@ -298,13 +301,13 @@ static int vmentry_l1d_flush_set(const char *s, const struct kernel_param *kp) 
{

	int l1tf, ret;



	if (!boot_cpu_has(X86_BUG_L1TF))

		return 0;



	l1tf = vmentry_l1d_flush_parse(s);

	if (l1tf < 0)

		return l1tf;



	if (!boot_cpu_has(X86_BUG_L1TF))

		return 0;



	/*

	 * Has vmx_init() run already? If not then this is the pre init

	 * parameter parsing. In that case just store the value and let
@@ -324,6 +327,9 @@ static int vmentry_l1d_flush_set(const char *s, const struct kernel_param *kp) 


static int vmentry_l1d_flush_get(char *s, const struct kernel_param *kp)

{

	if (WARN_ON_ONCE(l1tf_vmx_mitigation >= ARRAY_SIZE(vmentry_l1d_param)))

		return sprintf(s, "???\n");



	return sprintf(s, "%s\n", vmentry_l1d_param[l1tf_vmx_mitigation].option);

}

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