MIPS: KVM: Fix NULL pointer dereference

After commit 45c7e8af4a5e3f0bea4ac209 ("MIPS: Remove KVM_TE support") we
get a NULL pointer dereference when creating a KVM guest:

[  146.243409] Starting KVM with MIPS VZ extensions
[  149.849151] CPU 3 Unable to handle kernel paging request at virtual address 0000000000000300, epc == ffffffffc06356ec, ra == ffffffffc063568c
[  149.849177] Oops[#1]:
[  149.849182] CPU: 3 PID: 2265 Comm: qemu-system-mip Not tainted 6.4.0-rc3+ #1671
[  149.849188] Hardware name: THTF CX TL630 Series/THTF-LS3A4000-7A1000-ML4A, BIOS KL4.1F.TF.D.166.201225.R 12/25/2020
[  149.849192] $ 0   : 0000000000000000 000000007400cce0 0000000000400004 ffffffff8119c740
[  149.849209] $ 4   : 000000007400cce1 000000007400cce1 0000000000000000 0000000000000000
[  149.849221] $ 8   : 000000240058bb36 ffffffff81421ac0 0000000000000000 0000000000400dc0
[  149.849233] $12   : 9800000102a07cc8 ffffffff80e40e38 0000000000000001 0000000000400dc0
[  149.849245] $16   : 0000000000000000 9800000106cd0000 9800000106cd0000 9800000100cce000
[  149.849257] $20   : ffffffffc0632b28 ffffffffc05b31b0 9800000100ccca00 0000000000400000
[  149.849269] $24   : 9800000106cd09ce ffffffff802f69d0
[  149.849281] $28   : 9800000102a04000 9800000102a07cd0 98000001106a8000 ffffffffc063568c
[  149.849293] Hi    : 00000335b2111e66
[  149.849295] Lo    : 6668d90061ae0ae9
[  149.849298] epc   : ffffffffc06356ec kvm_vz_vcpu_setup+0xc4/0x328 [kvm]
[  149.849324] ra    : ffffffffc063568c kvm_vz_vcpu_setup+0x64/0x328 [kvm]
[  149.849336] Status: 7400cce3 KX SX UX KERNEL EXL IE
[  149.849351] Cause : 1000000c (ExcCode 03)
[  149.849354] BadVA : 0000000000000300
[  149.849357] PrId  : 0014c004 (ICT Loongson-3)
[  149.849360] Modules linked in: kvm nfnetlink_queue nfnetlink_log nfnetlink fuse sha256_generic libsha256 cfg80211 rfkill binfmt_misc vfat fat snd_hda_codec_hdmi input_leds led_class snd_hda_intel snd_intel_dspcfg snd_hda_codec snd_hda_core snd_pcm snd_timer snd serio_raw xhci_pci radeon drm_suballoc_helper drm_display_helper xhci_hcd ip_tables x_tables
[  149.849432] Process qemu-system-mip (pid: 2265, threadinfo=00000000ae2982d2, task=0000000038e09ad4, tls=000000ffeba16030)
[  149.849439] Stack : 9800000000000003 9800000100ccca00 9800000100ccc000 ffffffffc062cef4
[  149.849453]         9800000102a07d18 c89b63a7ab338e00 0000000000000000 ffffffff811a0000
[  149.849465]         0000000000000000 9800000106cd0000 ffffffff80e59938 98000001106a8920
[  149.849476]         ffffffff80e57f30 ffffffffc062854c ffffffff811a0000 9800000102bf4240
[  149.849488]         ffffffffc05b0000 ffffffff80e3a798 000000ff78000000 000000ff78000010
[  149.849500]         0000000000000255 98000001021f7de0 98000001023f0078 ffffffff81434000
[  149.849511]         0000000000000000 0000000000000000 9800000102ae0000 980000025e92ae28
[  149.849523]         0000000000000000 c89b63a7ab338e00 0000000000000001 ffffffff8119dce0
[  149.849535]         000000ff78000010 ffffffff804f3d3c 9800000102a07eb0 0000000000000255
[  149.849546]         0000000000000000 ffffffff8049460c 000000ff78000010 0000000000000255
[  149.849558]         ...
[  149.849565] Call Trace:
[  149.849567] [<ffffffffc06356ec>] kvm_vz_vcpu_setup+0xc4/0x328 [kvm]
[  149.849586] [<ffffffffc062cef4>] kvm_arch_vcpu_create+0x184/0x228 [kvm]
[  149.849605] [<ffffffffc062854c>] kvm_vm_ioctl+0x64c/0xf28 [kvm]
[  149.849623] [<ffffffff805209c0>] sys_ioctl+0xc8/0x118
[  149.849631] [<ffffffff80219eb0>] syscall_common+0x34/0x58

The root cause is the deletion of kvm_mips_commpage_init() leaves vcpu
->arch.cop0 NULL. So fix it by making cop0 from a pointer to an embedded
object.

Fixes: 45c7e8af4a5e3f0bea4ac209 ("MIPS: Remove KVM_TE support")
Cc: stable@vger.kernel.org
Reported-by: Yu Zhao <yuzhao@google.com>
Suggested-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

1 files changed, 11 insertions, 11 deletions

diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c
index edaec93a1a1f..e64372b8f66a 100644
--- a/arch/mips/kvm/emulate.c
+++ b/arch/mips/kvm/emulate.c
@@ -312,7 +312,7 @@ int kvm_get_badinstrp(u32 *opc, struct kvm_vcpu *vcpu, u32 *out)
  */
 int kvm_mips_count_disabled(struct kvm_vcpu *vcpu)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 
 	return	(vcpu->arch.count_ctl & KVM_REG_MIPS_COUNT_CTL_DC) ||
 		(kvm_read_c0_guest_cause(cop0) & CAUSEF_DC);
@@ -384,7 +384,7 @@ static inline ktime_t kvm_mips_count_time(struct kvm_vcpu *vcpu)
  */
 static u32 kvm_mips_read_count_running(struct kvm_vcpu *vcpu, ktime_t now)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 	ktime_t expires, threshold;
 	u32 count, compare;
 	int running;
@@ -444,7 +444,7 @@ static u32 kvm_mips_read_count_running(struct kvm_vcpu *vcpu, ktime_t now)
  */
 u32 kvm_mips_read_count(struct kvm_vcpu *vcpu)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 
 	/* If count disabled just read static copy of count */
 	if (kvm_mips_count_disabled(vcpu))
@@ -502,7 +502,7 @@ ktime_t kvm_mips_freeze_hrtimer(struct kvm_vcpu *vcpu, u32 *count)
 static void kvm_mips_resume_hrtimer(struct kvm_vcpu *vcpu,
 				    ktime_t now, u32 count)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 	u32 compare;
 	u64 delta;
 	ktime_t expire;
@@ -603,7 +603,7 @@ resume:
  */
 void kvm_mips_write_count(struct kvm_vcpu *vcpu, u32 count)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 	ktime_t now;
 
 	/* Calculate bias */
@@ -649,7 +649,7 @@ void kvm_mips_init_count(struct kvm_vcpu *vcpu, unsigned long count_hz)
  */
 int kvm_mips_set_count_hz(struct kvm_vcpu *vcpu, s64 count_hz)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 	int dc;
 	ktime_t now;
 	u32 count;
@@ -696,7 +696,7 @@ int kvm_mips_set_count_hz(struct kvm_vcpu *vcpu, s64 count_hz)
  */
 void kvm_mips_write_compare(struct kvm_vcpu *vcpu, u32 compare, bool ack)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 	int dc;
 	u32 old_compare = kvm_read_c0_guest_compare(cop0);
 	s32 delta = compare - old_compare;
@@ -779,7 +779,7 @@ void kvm_mips_write_compare(struct kvm_vcpu *vcpu, u32 compare, bool ack)
  */
 static ktime_t kvm_mips_count_disable(struct kvm_vcpu *vcpu)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 	u32 count;
 	ktime_t now;
 
@@ -806,7 +806,7 @@ static ktime_t kvm_mips_count_disable(struct kvm_vcpu *vcpu)
  */
 void kvm_mips_count_disable_cause(struct kvm_vcpu *vcpu)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 
 	kvm_set_c0_guest_cause(cop0, CAUSEF_DC);
 	if (!(vcpu->arch.count_ctl & KVM_REG_MIPS_COUNT_CTL_DC))
@@ -826,7 +826,7 @@ void kvm_mips_count_disable_cause(struct kvm_vcpu *vcpu)
  */
 void kvm_mips_count_enable_cause(struct kvm_vcpu *vcpu)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 	u32 count;
 
 	kvm_clear_c0_guest_cause(cop0, CAUSEF_DC);
@@ -852,7 +852,7 @@ void kvm_mips_count_enable_cause(struct kvm_vcpu *vcpu)
  */
 int kvm_mips_set_count_ctl(struct kvm_vcpu *vcpu, s64 count_ctl)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 	s64 changed = count_ctl ^ vcpu->arch.count_ctl;
 	s64 delta;
 	ktime_t expire, now;