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From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
	Brijesh Singh <brijesh.singh@amd.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	John Allen <john.allen@amd.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, linux-crypto@vger.kernel.org,
	linux-kernel@vger.kernel.org, Borislav Petkov <bp@suse.de>
Subject: [PATCH 2/5] crypto: ccp: Reject SEV commands with mismatching command buffer
Date: Fri,  2 Apr 2021 16:36:59 -0700
Message-ID: <20210402233702.3291792-3-seanjc@google.com> (raw)
In-Reply-To: <20210402233702.3291792-1-seanjc@google.com>

WARN on and reject SEV commands that provide a valid data pointer, but do
not have a known, non-zero length.  And conversely, reject commands that
take a command buffer but none is provided.

Aside from sanity checking intput, disallowing a non-null pointer without
a non-zero size will allow a future patch to cleanly handle vmalloc'd
data by copying the data to an internal __pa() friendly buffer.

Note, this also effectively prevents callers from using commands that
have a non-zero length and are not known to the kernel.  This is not an
explicit goal, but arguably the side effect is a good thing from the
kernel's perspective.

Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 drivers/crypto/ccp/sev-dev.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 6556d220713b..4c513318f16a 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -141,6 +141,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
 	struct sev_device *sev;
 	unsigned int phys_lsb, phys_msb;
 	unsigned int reg, ret = 0;
+	int buf_len;
 
 	if (!psp || !psp->sev_data)
 		return -ENODEV;
@@ -150,7 +151,11 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
 
 	sev = psp->sev_data;
 
-	if (data && WARN_ON_ONCE(is_vmalloc_addr(data)))
+	buf_len = sev_cmd_buffer_len(cmd);
+	if (WARN_ON_ONCE(!!data != !!buf_len))
+		return -EINVAL;
+
+	if (WARN_ON_ONCE(data && is_vmalloc_addr(data)))
 		return -EINVAL;
 
 	/* Get the physical address of the command buffer */
@@ -161,7 +166,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
 		cmd, phys_msb, phys_lsb, psp_timeout);
 
 	print_hex_dump_debug("(in):  ", DUMP_PREFIX_OFFSET, 16, 2, data,
-			     sev_cmd_buffer_len(cmd), false);
+			     buf_len, false);
 
 	iowrite32(phys_lsb, sev->io_regs + sev->vdata->cmdbuff_addr_lo_reg);
 	iowrite32(phys_msb, sev->io_regs + sev->vdata->cmdbuff_addr_hi_reg);
@@ -197,7 +202,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
 	}
 
 	print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data,
-			     sev_cmd_buffer_len(cmd), false);
+			     buf_len, false);
 
 	return ret;
 }
-- 
2.31.0.208.g409f899ff0-goog


  parent reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-02 23:36 [PATCH 0/5] ccp: KVM: SVM: Use stack for SEV command buffers Sean Christopherson
2021-04-02 23:36 ` [PATCH 1/5] crypto: ccp: Detect and reject vmalloc addresses destined for PSP Sean Christopherson
2021-04-04  6:31   ` Christophe Leroy
2021-04-02 23:36 ` Sean Christopherson [this message]
2021-04-03 17:02   ` [PATCH 2/5] crypto: ccp: Reject SEV commands with mismatching command buffer Christophe Leroy
2021-04-05 16:26   ` Tom Lendacky
2021-04-05 16:33     ` Sean Christopherson
2021-04-05 16:37       ` Tom Lendacky
2021-04-02 23:37 ` [PATCH 3/5] crypto: ccp: Play nice with vmalloc'd memory for SEV command structs Sean Christopherson
2021-04-03 17:05   ` Christophe Leroy
2021-04-03 17:13   ` Christophe Leroy
2021-04-04  6:48   ` Christophe Leroy
2021-04-05 15:06     ` Sean Christopherson
2021-04-05 16:01       ` Brijesh Singh
2021-04-02 23:37 ` [PATCH 4/5] crypto: ccp: Use the stack for small SEV command buffers Sean Christopherson
2021-04-02 23:37 ` [PATCH 5/5] KVM: SVM: Allocate SEV command structures on local stack Sean Christopherson
2021-04-04 19:54 ` [PATCH 0/5] ccp: KVM: SVM: Use stack for SEV command buffers Brijesh Singh

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