linux-kernel - [PATCH] KVM: SVM: Use kzalloc for sev ioctl interfaces to prevent kernel memory leak.

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Date:   Thu, 12 May 2022 20:23:28 +0000
From:   Ashish Kalra <Ashish.Kalra@....com>
To:     <pbonzini@...hat.com>
CC:     <seanjc@...gle.com>, <tglx@...utronix.de>, <mingo@...hat.com>,
        <hpa@...or.com>, <joro@...tes.org>, <Thomas.Lendacky@....com>,
        <bp@...en8.de>, <x86@...nel.org>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <theflow@...gle.com>,
        <rientjes@...gle.com>, <pgonda@...gle.com>, <john.allen@....com>
Subject: [PATCH] KVM: SVM: Use kzalloc for sev ioctl interfaces to prevent kernel memory leak.

From: Ashish Kalra <ashish.kalra@....com>

For some sev ioctl interfaces, the length parameter that is passed maybe
less than or equal to SEV_FW_BLOB_MAX_SIZE, but larger than the data
that PSP firmware returns. In this case, kmalloc will allocate memory
that is the size of the input rather than the size of the data.
Since PSP firmware doesn't fully overwrite the allocated buffer, these
sev ioctl interface may return uninitialized kernel slab memory.

Reported-by: Andy Nguyen <theflow@...gle.com>
Suggested-by: David Rientjes <rientjes@...gle.com>
Suggested-by: Peter Gonda <pgonda@...gle.com>
Cc: kvm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Ashish Kalra <ashish.kalra@....com>
---
 arch/x86/kvm/svm/sev.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 7c392873626f..d93dab5c9ce1 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -688,7 +688,7 @@ static int sev_launch_measure(struct kvm *kvm, struct kvm_sev_cmd *argp)
 		if (params.len > SEV_FW_BLOB_MAX_SIZE)
 			return -EINVAL;
 
-		blob = kmalloc(params.len, GFP_KERNEL_ACCOUNT);
+		blob = kzalloc(params.len, GFP_KERNEL_ACCOUNT);
 		if (!blob)
 			return -ENOMEM;
 
@@ -808,7 +808,7 @@ static int __sev_dbg_decrypt_user(struct kvm *kvm, unsigned long paddr,
 	if (!IS_ALIGNED(dst_paddr, 16) ||
 	    !IS_ALIGNED(paddr,     16) ||
 	    !IS_ALIGNED(size,      16)) {
-		tpage = (void *)alloc_page(GFP_KERNEL);
+		tpage = (void *)alloc_page(GFP_KERNEL | __GFP_ZERO);
 		if (!tpage)
 			return -ENOMEM;
 
@@ -1094,7 +1094,7 @@ static int sev_get_attestation_report(struct kvm *kvm, struct kvm_sev_cmd *argp)
 		if (params.len > SEV_FW_BLOB_MAX_SIZE)
 			return -EINVAL;
 
-		blob = kmalloc(params.len, GFP_KERNEL_ACCOUNT);
+		blob = kzalloc(params.len, GFP_KERNEL_ACCOUNT);
 		if (!blob)
 			return -ENOMEM;
 
-- 
2.25.1