diff options
| author | Vasiliy Kovalev <kovalev@altlinux.org> | 2026-01-24 01:28:01 +0300 |
|---|---|---|
| committer | Sasha Levin <sashal@kernel.org> | 2026-03-04 07:21:11 -0500 |
| commit | 708e20c66b2761d878a2bc3c7534e7f814e4dec5 (patch) | |
| tree | 69fd2bfe51777dca0f07ef1c01e53303fc76fc99 | |
| parent | a6f660d62bc12e8a7d9d81f9069b515ff79f2dcc (diff) | |
KVM: x86: Add SRCU protection for reading PDPTRs in __get_sregs2()
[ Upstream commit 95d848dc7e639988dbb385a8cba9b484607cf98c ]
Add SRCU read-side protection when reading PDPTR registers in
__get_sregs2().
Reading PDPTRs may trigger access to guest memory:
kvm_pdptr_read() -> svm_cache_reg() -> load_pdptrs() ->
kvm_vcpu_read_guest_page() -> kvm_vcpu_gfn_to_memslot()
kvm_vcpu_gfn_to_memslot() dereferences memslots via __kvm_memslots(),
which uses srcu_dereference_check() and requires either kvm->srcu or
kvm->slots_lock to be held. Currently only vcpu->mutex is held,
triggering lockdep warning:
=============================
WARNING: suspicious RCU usage in kvm_vcpu_gfn_to_memslot
6.12.59+ #3 Not tainted
include/linux/kvm_host.h:1062 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz.5.1717/15100:
#0: ff1100002f4b00b0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x1d5/0x1590
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0xf0/0x120 lib/dump_stack.c:120
lockdep_rcu_suspicious+0x1e3/0x270 kernel/locking/lockdep.c:6824
__kvm_memslots include/linux/kvm_host.h:1062 [inline]
__kvm_memslots include/linux/kvm_host.h:1059 [inline]
kvm_vcpu_memslots include/linux/kvm_host.h:1076 [inline]
kvm_vcpu_gfn_to_memslot+0x518/0x5e0 virt/kvm/kvm_main.c:2617
kvm_vcpu_read_guest_page+0x27/0x50 virt/kvm/kvm_main.c:3302
load_pdptrs+0xff/0x4b0 arch/x86/kvm/x86.c:1065
svm_cache_reg+0x1c9/0x230 arch/x86/kvm/svm/svm.c:1688
kvm_pdptr_read arch/x86/kvm/kvm_cache_regs.h:141 [inline]
__get_sregs2 arch/x86/kvm/x86.c:11784 [inline]
kvm_arch_vcpu_ioctl+0x3e20/0x4aa0 arch/x86/kvm/x86.c:6279
kvm_vcpu_ioctl+0x856/0x1590 virt/kvm/kvm_main.c:4663
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl fs/ioctl.c:893 [inline]
__x64_sys_ioctl+0x18b/0x210 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xbd/0x1d0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: stable@vger.kernel.org
Fixes: 6dba94035203 ("KVM: x86: Introduce KVM_GET_SREGS2 / KVM_SET_SREGS2")
Signed-off-by: Vasiliy Kovalev <kovalev@altlinux.org>
Link: https://patch.msgid.link/20260123222801.646123-1-kovalev@altlinux.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | arch/x86/kvm/x86.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 89df215ebf28..00bbee40dbec 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -11437,9 +11437,11 @@ static void __get_sregs2(struct kvm_vcpu *vcpu, struct kvm_sregs2 *sregs2) return; if (is_pae_paging(vcpu)) { + kvm_vcpu_srcu_read_lock(vcpu); for (i = 0 ; i < 4 ; i++) sregs2->pdptrs[i] = kvm_pdptr_read(vcpu, i); sregs2->flags |= KVM_SREGS2_FLAGS_PDPTRS_VALID; + kvm_vcpu_srcu_read_unlock(vcpu); } } |