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, 8 insertions, 8 deletions

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 884be4ef99dc..aa5583a7b05b 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -649,7 +649,7 @@ static int kvm_mips_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices)
 static int kvm_mips_get_reg(struct kvm_vcpu *vcpu,
 			    const struct kvm_one_reg *reg)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 	struct mips_fpu_struct *fpu = &vcpu->arch.fpu;
 	int ret;
 	s64 v;
@@ -761,7 +761,7 @@ static int kvm_mips_get_reg(struct kvm_vcpu *vcpu,
 static int kvm_mips_set_reg(struct kvm_vcpu *vcpu,
 			    const struct kvm_one_reg *reg)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 	struct mips_fpu_struct *fpu = &vcpu->arch.fpu;
 	s64 v;
 	s64 vs[2];
@@ -1086,7 +1086,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
 {
 	return kvm_mips_pending_timer(vcpu) ||
-		kvm_read_c0_guest_cause(vcpu->arch.cop0) & C_TI;
+		kvm_read_c0_guest_cause(&vcpu->arch.cop0) & C_TI;
 }
 
 int kvm_arch_vcpu_dump_regs(struct kvm_vcpu *vcpu)
@@ -1110,7 +1110,7 @@ int kvm_arch_vcpu_dump_regs(struct kvm_vcpu *vcpu)
 	kvm_debug("\thi: 0x%08lx\n", vcpu->arch.hi);
 	kvm_debug("\tlo: 0x%08lx\n", vcpu->arch.lo);
 
-	cop0 = vcpu->arch.cop0;
+	cop0 = &vcpu->arch.cop0;
 	kvm_debug("\tStatus: 0x%08x, Cause: 0x%08x\n",
 		  kvm_read_c0_guest_status(cop0),
 		  kvm_read_c0_guest_cause(cop0));
@@ -1232,7 +1232,7 @@ static int __kvm_mips_handle_exit(struct kvm_vcpu *vcpu)
 
 	case EXCCODE_TLBS:
 		kvm_debug("TLB ST fault:  cause %#x, status %#x, PC: %p, BadVaddr: %#lx\n",
-			  cause, kvm_read_c0_guest_status(vcpu->arch.cop0), opc,
+			  cause, kvm_read_c0_guest_status(&vcpu->arch.cop0), opc,
 			  badvaddr);
 
 		++vcpu->stat.tlbmiss_st_exits;
@@ -1304,7 +1304,7 @@ static int __kvm_mips_handle_exit(struct kvm_vcpu *vcpu)
 		kvm_get_badinstr(opc, vcpu, &inst);
 		kvm_err("Exception Code: %d, not yet handled, @ PC: %p, inst: 0x%08x  BadVaddr: %#lx Status: %#x\n",
 			exccode, opc, inst, badvaddr,
-			kvm_read_c0_guest_status(vcpu->arch.cop0));
+			kvm_read_c0_guest_status(&vcpu->arch.cop0));
 		kvm_arch_vcpu_dump_regs(vcpu);
 		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
 		ret = RESUME_HOST;
@@ -1377,7 +1377,7 @@ int noinstr kvm_mips_handle_exit(struct kvm_vcpu *vcpu)
 /* Enable FPU for guest and restore context */
 void kvm_own_fpu(struct kvm_vcpu *vcpu)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 	unsigned int sr, cfg5;
 
 	preempt_disable();
@@ -1421,7 +1421,7 @@ void kvm_own_fpu(struct kvm_vcpu *vcpu)
 /* Enable MSA for guest and restore context */
 void kvm_own_msa(struct kvm_vcpu *vcpu)
 {
-	struct mips_coproc *cop0 = vcpu->arch.cop0;
+	struct mips_coproc *cop0 = &vcpu->arch.cop0;
 	unsigned int sr, cfg5;
 
 	preempt_disable();