From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>
Cc: Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, llvm@lists.linux.dev,
linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Tadeusz Struk <tadeusz.struk@linaro.org>,
syzbot+6cde2282daa792c49ab8@syzkaller.appspotmail.com
Subject: [PATCH v2 4/5] KVM: x86: Use __try_cmpxchg_user() to emulate atomic accesses
Date: Wed, 2 Feb 2022 00:49:44 +0000 [thread overview]
Message-ID: <20220202004945.2540433-5-seanjc@google.com> (raw)
In-Reply-To: <20220202004945.2540433-1-seanjc@google.com>
Use the recently introduce __try_cmpxchg_user() to emulate atomic guest
accesses via the associated userspace address instead of mapping the
backing pfn into kernel address space. Using kvm_vcpu_map() is unsafe as
it does not coordinate with KVM's mmu_notifier to ensure the hva=>pfn
translation isn't changed/unmapped in the memremap() path, i.e. when
there's no struct page and thus no elevated refcount.
Fixes: 42e35f8072c3 ("KVM/X86: Use kvm_vcpu_map in emulator_cmpxchg_emulated")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/x86.c | 35 ++++++++++++++---------------------
1 file changed, 14 insertions(+), 21 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 74b53a16f38a..c9cac3100f77 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7155,15 +7155,8 @@ static int emulator_write_emulated(struct x86_emulate_ctxt *ctxt,
exception, &write_emultor);
}
-#define CMPXCHG_TYPE(t, ptr, old, new) \
- (cmpxchg((t *)(ptr), *(t *)(old), *(t *)(new)) == *(t *)(old))
-
-#ifdef CONFIG_X86_64
-# define CMPXCHG64(ptr, old, new) CMPXCHG_TYPE(u64, ptr, old, new)
-#else
-# define CMPXCHG64(ptr, old, new) \
- (cmpxchg64((u64 *)(ptr), *(u64 *)(old), *(u64 *)(new)) == *(u64 *)(old))
-#endif
+#define emulator_try_cmpxchg_user(t, ptr, old, new) \
+ (__try_cmpxchg_user((t __user *)(ptr), (t *)(old), *(t *)(new), efault ## t))
static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
unsigned long addr,
@@ -7172,12 +7165,11 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
unsigned int bytes,
struct x86_exception *exception)
{
- struct kvm_host_map map;
struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
u64 page_line_mask;
+ unsigned long hva;
gpa_t gpa;
- char *kaddr;
- bool exchanged;
+ int r;
/* guests cmpxchg8b have to be emulated atomically */
if (bytes > 8 || (bytes & (bytes - 1)))
@@ -7201,31 +7193,32 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
if (((gpa + bytes - 1) & page_line_mask) != (gpa & page_line_mask))
goto emul_write;
- if (kvm_vcpu_map(vcpu, gpa_to_gfn(gpa), &map))
+ hva = kvm_vcpu_gfn_to_hva(vcpu, gpa_to_gfn(gpa));
+ if (kvm_is_error_hva(addr))
goto emul_write;
- kaddr = map.hva + offset_in_page(gpa);
+ hva += offset_in_page(gpa);
switch (bytes) {
case 1:
- exchanged = CMPXCHG_TYPE(u8, kaddr, old, new);
+ r = emulator_try_cmpxchg_user(u8, hva, old, new);
break;
case 2:
- exchanged = CMPXCHG_TYPE(u16, kaddr, old, new);
+ r = emulator_try_cmpxchg_user(u16, hva, old, new);
break;
case 4:
- exchanged = CMPXCHG_TYPE(u32, kaddr, old, new);
+ r = emulator_try_cmpxchg_user(u32, hva, old, new);
break;
case 8:
- exchanged = CMPXCHG64(kaddr, old, new);
+ r = emulator_try_cmpxchg_user(u64, hva, old, new);
break;
default:
BUG();
}
- kvm_vcpu_unmap(vcpu, &map, true);
-
- if (!exchanged)
+ if (r < 0)
+ goto emul_write;
+ if (r)
return X86EMUL_CMPXCHG_FAILED;
kvm_page_track_write(vcpu, gpa, new, bytes);
--
2.35.0.rc2.247.g8bbb082509-goog
next prev parent reply other threads:[~2022-02-02 0:50 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-02 0:49 [PATCH v2 0/5] x86: uaccess CMPXCHG + KVM bug fixes Sean Christopherson
2022-02-02 0:49 ` [PATCH v2 1/5] Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug Sean Christopherson
2022-02-02 0:49 ` [PATCH v2 2/5] x86/uaccess: Implement macros for CMPXCHG on user addresses Sean Christopherson
2022-02-02 0:49 ` [PATCH v2 3/5] KVM: x86: Use __try_cmpxchg_user() to update guest PTE A/D bits Sean Christopherson
2022-02-02 0:49 ` Sean Christopherson [this message]
2022-05-12 10:14 ` [PATCH] KVM: x86: fix a typo in __try_cmpxchg_user that caused cmpxchg to be not atomic Maxim Levitsky
2022-05-12 12:45 ` Vitaly Kuznetsov
2022-05-12 13:48 ` Sean Christopherson
2022-05-12 15:47 ` Paolo Bonzini
2022-05-12 21:27 ` Sean Christopherson
2022-05-16 13:14 ` Maxim Levitsky
2022-05-16 14:03 ` Sean Christopherson
2022-02-02 0:49 ` [PATCH v2 5/5] KVM: x86: Bail to userspace if emulation of atomic user access faults Sean Christopherson
2022-04-01 7:53 ` [PATCH v2 0/5] x86: uaccess CMPXCHG + KVM bug fixes Paolo Bonzini
2022-04-01 17:07 ` Tadeusz Struk
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220202004945.2540433-5-seanjc@google.com \
--to=seanjc@google.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=llvm@lists.linux.dev \
--cc=nathan@kernel.org \
--cc=ndesaulniers@google.com \
--cc=pbonzini@redhat.com \
--cc=peterz@infradead.org \
--cc=syzbot+6cde2282daa792c49ab8@syzkaller.appspotmail.com \
--cc=tadeusz.struk@linaro.org \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).