From patchwork Wed Mar 20 00:15:40 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 13597130 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ACC67801 for ; Wed, 20 Mar 2024 00:15:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710893749; cv=none; b=E3LLfv68wSDiOGbmk0+7FMDPskNc4M1DH1/qzCpSLjnYs0fPmcNH71vj5W2NUK7QHdAOVs95aFftxP2g5C3YpnDZRGOm1J/QJMHd7oofSPKJbqj3NTgSC33o8V7xPyyztv147wnNloPYoUcLVt1RE9qthHSp3of4jv09ORG9LLs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710893749; c=relaxed/simple; bh=YyvaQnQJdiY8Q7R4CiMT+UezwhRShOi5cPHWawz2f9s=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=liQClu3iyTuzo7sgUT/iTU89HwOaQln5S1cpgEeQUKCEZZ0ot1uADdAqkHuv28AhQghhNmPfN1cEPHi/DnmTUIOtWRPrWXyiSheD3TqG066QLFbDCRU3c31GTkLlwQZYdvXI51NrmZI4KV4ydBHP5nBqmPmOdmm4ShynJfrmem0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=dft+e1h4; arc=none smtp.client-ip=209.85.128.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="dft+e1h4" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-60cbba6f571so118210057b3.1 for ; Tue, 19 Mar 2024 17:15:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1710893746; x=1711498546; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=i9kVuQFqGWveMSm1GQ8GItZlMlvWOz6Hx+yWjI9J9D0=; b=dft+e1h4Nh8crW2PYZK9Wc/PQ3LW8gKEhxHBn0x64lcmPtwmgTIW21PgdkJ5S42sS/ Pmlcadj0i4zwmPC1fx5sFT3boRtHkaV3jogEkosH/84RWf1nGwB9Sr6xtk3vHuO2dmLO WNyCeHEgy/5Be4Tl9LzRkX1AuVXcnAGwhsw2ezspFv0MFKQavvxySNpZzQlAmF6KbhQu JF46oCgdu5DbrC3IbFadILDqW6xUnfXjqw6zcBY40NCxmm8ey6DUaQkgvLXPIYnesBEL UUfbP8gv/yVvEyBij/bRHX3ejd96LVCEv79BVUyBaTKGlaP4EL8eAHlEtuk9DHgIlTGu DzEA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1710893746; x=1711498546; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=i9kVuQFqGWveMSm1GQ8GItZlMlvWOz6Hx+yWjI9J9D0=; b=BDgPzy/AeyHg6J06sDe1YVX8oI4omEBxPnrBgOIYmpkpqR8xzFaMOrdxRFg95FJW8P zAglyb10Qo3X64tbU/ASSgbw5NEPpZq2bH3K/Sy85YD3fBjyBat1bqO8xmQoD4BrYBUB EIjRq+lWdRlzdpaKOml0sLTwEknBq/MeYzKx3ybz11tT4dRJd0ddLPA73DT1tBrmxtSb xGf8837ODpWaW2LfnUVFPDVNvc3YGOefTsXUVGtAbJV3RabJNwAcMatdGZF8Y9ACWCWk 9T9Kkj5icNuDku5sK5echR0ESTeB8KLknPK733YXHdebvn1DqL/qZhm2ZYhvLxjL35EG dIog== X-Gm-Message-State: AOJu0YyrsoIPCN81gIOGCVvPBuTfLPL/+ajkmv0xRZNhUrNdoV/1Hr7w 453E4BSu+ZDDae03q6SpWZ8QJgMEJtqCcRDKolCDcdjp5eu9jQsUZDDMq4An9h1xz7yKBop6H38 VFg== X-Google-Smtp-Source: AGHT+IF0fWCYk6aKjKkWi7E/zeckbR9RpV3kVXyudQGGVegRGO/dQ5GmRozoHp9hQmE7pRVxq/v7aqYk34A= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6902:1507:b0:dcd:ad52:6932 with SMTP id q7-20020a056902150700b00dcdad526932mr4330305ybu.5.1710893746735; Tue, 19 Mar 2024 17:15:46 -0700 (PDT) Reply-To: Sean Christopherson Date: Tue, 19 Mar 2024 17:15:40 -0700 In-Reply-To: <20240320001542.3203871-1-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240320001542.3203871-1-seanjc@google.com> X-Mailer: git-send-email 2.44.0.291.gc1ea87d7ee-goog Message-ID: <20240320001542.3203871-2-seanjc@google.com> Subject: [PATCH 1/3] KVM: Add helpers to consolidate gfn_to_pfn_cache's page split check From: Sean Christopherson To: Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Sean Christopherson , syzbot+106a4f72b0474e1d1b33@syzkaller.appspotmail.com, David Woodhouse , Paul Durrant Add a helper to check that the incoming length for a gfn_to_pfn_cache is valid with respect to the cache's GPA and/or HVA. To avoid activating a cache with a bogus GPA, a future fix will fork the page split check in the inner refresh path into activate() and the public rerfresh() APIs, at which point KVM will check the length in three separate places. Deliberately keep the "page offset" logic open coded, as the only other path that consumes the offset, __kvm_gpc_refresh(), already needs to differentiate between GPA-based and HVA-based caches, and it's not obvious that using a helper is a net positive in overall code readability. Note, for GPA-based caches, this has a subtle side effect of using the GPA instead of the resolved HVA in the check() path, but that should be a nop as the HVA offset is derived from the GPA, i.e. the two offsets are identical, barring a KVM bug. Signed-off-by: Sean Christopherson Reviewed-by: David Woodhouse Reviewed-by: Paul Durrant --- virt/kvm/pfncache.c | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-) diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c index 4e07112a24c2..8f2121b5f2a0 100644 --- a/virt/kvm/pfncache.c +++ b/virt/kvm/pfncache.c @@ -57,6 +57,19 @@ void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, unsigned long start, spin_unlock(&kvm->gpc_lock); } +static bool kvm_gpc_is_valid_len(gpa_t gpa, unsigned long uhva, + unsigned long len) +{ + unsigned long offset = kvm_is_error_gpa(gpa) ? offset_in_page(uhva) : + offset_in_page(gpa); + + /* + * The cached access must fit within a single page. The 'len' argument + * to activate() and refresh() exists only to enforce that. + */ + return offset + len <= PAGE_SIZE; +} + bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len) { struct kvm_memslots *slots = kvm_memslots(gpc->kvm); @@ -74,7 +87,7 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len) if (kvm_is_error_hva(gpc->uhva)) return false; - if (offset_in_page(gpc->uhva) + len > PAGE_SIZE) + if (!kvm_gpc_is_valid_len(gpc->gpa, gpc->uhva, len)) return false; if (!gpc->valid) @@ -247,13 +260,7 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned l if (WARN_ON_ONCE(kvm_is_error_gpa(gpa) == kvm_is_error_hva(uhva))) return -EINVAL; - /* - * The cached acces must fit within a single page. The 'len' argument - * exists only to enforce that. - */ - page_offset = kvm_is_error_gpa(gpa) ? offset_in_page(uhva) : - offset_in_page(gpa); - if (page_offset + len > PAGE_SIZE) + if (!kvm_gpc_is_valid_len(gpa, uhva, len)) return -EINVAL; lockdep_assert_held(&gpc->refresh_lock); @@ -270,6 +277,8 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned l old_uhva = PAGE_ALIGN_DOWN(gpc->uhva); if (kvm_is_error_gpa(gpa)) { + page_offset = offset_in_page(uhva); + gpc->gpa = INVALID_GPA; gpc->memslot = NULL; gpc->uhva = PAGE_ALIGN_DOWN(uhva); @@ -279,6 +288,8 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned l } else { struct kvm_memslots *slots = kvm_memslots(gpc->kvm); + page_offset = offset_in_page(gpa); + if (gpc->gpa != gpa || gpc->generation != slots->generation || kvm_is_error_hva(gpc->uhva)) { gfn_t gfn = gpa_to_gfn(gpa); From patchwork Wed Mar 20 00:15:41 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 13597131 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6D1851C05 for ; 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Tue, 19 Mar 2024 17:15:48 -0700 (PDT) Reply-To: Sean Christopherson Date: Tue, 19 Mar 2024 17:15:41 -0700 In-Reply-To: <20240320001542.3203871-1-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240320001542.3203871-1-seanjc@google.com> X-Mailer: git-send-email 2.44.0.291.gc1ea87d7ee-goog Message-ID: <20240320001542.3203871-3-seanjc@google.com> Subject: [PATCH 2/3] KVM: Check validity of offset+length of gfn_to_pfn_cache prior to activation From: Sean Christopherson To: Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Sean Christopherson , syzbot+106a4f72b0474e1d1b33@syzkaller.appspotmail.com, David Woodhouse , Paul Durrant When activating a gfn_to_pfn_cache, verify that the offset+length is sane and usable before marking the cache active. Letting __kvm_gpc_refresh() detect the problem results in a cache being marked active without setting the GPA (or any other fields), which in turn results in KVM trying to refresh a cache with INVALID_GPA. Attempting to refresh a cache with INVALID_GPA isn't functionally problematic, but it runs afoul of the sanity check that exactly one of GPA or userspace HVA is valid, i.e. that a cache is either GPA-based or HVA-based. Reported-by: syzbot+106a4f72b0474e1d1b33@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/0000000000005fa5cc0613f1cebd@google.com Fixes: 721f5b0dda78 ("KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA") Cc: David Woodhouse Cc: Paul Durrant Signed-off-by: Sean Christopherson Reviewed-by: David Woodhouse Reviewed-by: Paul Durrant --- virt/kvm/pfncache.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c index 8f2121b5f2a0..91b0e329006b 100644 --- a/virt/kvm/pfncache.c +++ b/virt/kvm/pfncache.c @@ -245,8 +245,7 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc) return -EFAULT; } -static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long uhva, - unsigned long len) +static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long uhva) { unsigned long page_offset; bool unmap_old = false; @@ -260,9 +259,6 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned l if (WARN_ON_ONCE(kvm_is_error_gpa(gpa) == kvm_is_error_hva(uhva))) return -EINVAL; - if (!kvm_gpc_is_valid_len(gpa, uhva, len)) - return -EINVAL; - lockdep_assert_held(&gpc->refresh_lock); write_lock_irq(&gpc->lock); @@ -365,6 +361,9 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len) guard(mutex)(&gpc->refresh_lock); + if (!kvm_gpc_is_valid_len(gpc->gpa, gpc->uhva, len)) + return -EINVAL; + /* * If the GPA is valid then ignore the HVA, as a cache can be GPA-based * or HVA-based, not both. For GPA-based caches, the HVA will be @@ -372,7 +371,7 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len) */ uhva = kvm_is_error_gpa(gpc->gpa) ? gpc->uhva : KVM_HVA_ERR_BAD; - return __kvm_gpc_refresh(gpc, gpc->gpa, uhva, len); + return __kvm_gpc_refresh(gpc, gpc->gpa, uhva); } void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm) @@ -392,6 +391,9 @@ static int __kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned { struct kvm *kvm = gpc->kvm; + if (!kvm_gpc_is_valid_len(gpa, uhva, len)) + return -EINVAL; + guard(mutex)(&gpc->refresh_lock); if (!gpc->active) { @@ -411,7 +413,7 @@ static int __kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned gpc->active = true; write_unlock_irq(&gpc->lock); } - return __kvm_gpc_refresh(gpc, gpa, uhva, len); + return __kvm_gpc_refresh(gpc, gpa, uhva); } int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len) From patchwork Wed Mar 20 00:15:42 2024 Content-Type: text/plain; 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Tue, 19 Mar 2024 17:15:50 -0700 (PDT) Reply-To: Sean Christopherson Date: Tue, 19 Mar 2024 17:15:42 -0700 In-Reply-To: <20240320001542.3203871-1-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240320001542.3203871-1-seanjc@google.com> X-Mailer: git-send-email 2.44.0.291.gc1ea87d7ee-goog Message-ID: <20240320001542.3203871-4-seanjc@google.com> Subject: [PATCH 3/3] KVM: Explicitly disallow activatating a gfn_to_pfn_cache with INVALID_GPA From: Sean Christopherson To: Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Sean Christopherson , syzbot+106a4f72b0474e1d1b33@syzkaller.appspotmail.com, David Woodhouse , Paul Durrant Explicit disallow activating a gfn_to_pfn_cache with an error gpa, i.e. INVALID_GPA, to ensure that KVM doesn't mistake a GPA-based cache for an HVA-based cache (KVM uses INVALID_GPA as a magic value to differentiate between GPA-based and HVA-based caches). WARN if KVM attempts to activate a cache with INVALID_GPA, purely so that new caches need to at least consider what to do with a "bad" GPA, as all existing usage of kvm_gpc_activate() guarantees gpa != INVALID_GPA. I.e. removing the WARN in the future is completely reasonable if doing so would yield cleaner/better code overall. Signed-off-by: Sean Christopherson Reviewed-by: David Woodhouse Reviewed-by: Paul Durrant --- virt/kvm/pfncache.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c index 91b0e329006b..f618719644e0 100644 --- a/virt/kvm/pfncache.c +++ b/virt/kvm/pfncache.c @@ -418,6 +418,13 @@ static int __kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len) { + /* + * Explicitly disallow INVALID_GPA so that the magic value can be used + * by KVM to differentiate between GPA-based and HVA-based caches. + */ + if (WARN_ON_ONCE(kvm_is_error_gpa(gpa))) + return -EINVAL; + return __kvm_gpc_activate(gpc, gpa, KVM_HVA_ERR_BAD, len); }