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Date:   Wed, 12 Oct 2022 00:23:22 +0000
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Message-ID: <20221012002323.2015637-1-dionnaglaze@google.com>
Subject: [PATCH] virt/coco/sev-guest: Initialize err in handle_guest_request
From:   Dionna Glaze <dionnaglaze@google.com>
To:     x86@kernel.org, linux-kernel@vger.kernel.org
Cc:     Dionna Glaze <dionnaglaze@google.com>,
        Tom Lendacky <Thomas.Lendacky@amd.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Joerg Roedel <jroedel@suse.de>,
        Peter Gonda <pgonda@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Dave Hansen <dave.hansen@linux.intel.com>
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Precedence: bulk

The err variable may not be set in the call to snp_issue_guest_request,
yet it is unconditionally written back to fw_err if fw_err is non-null.
This is undefined behavior, and currently returns uninitialized kernel
stack memory to user space.

Cc: Tom Lendacky <Thomas.Lendacky@amd.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Peter Gonda <pgonda@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>

Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
---
 drivers/virt/coco/sevguest/sevguest.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/virt/coco/sevguest/sevguest.c b/drivers/virt/coco/sevguest/sevguest.c
index 112c0458cbda..7a62bfc063fc 100644
--- a/drivers/virt/coco/sevguest/sevguest.c
+++ b/drivers/virt/coco/sevguest/sevguest.c
@@ -307,7 +307,7 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 				u8 type, void *req_buf, size_t req_sz, void *resp_buf,
 				u32 resp_sz, __u64 *fw_err)
 {
-	unsigned long err;
+	unsigned long err = 0;
 	u64 seqno;
 	int rc;
 
-- 
2.38.0.rc1.362.ged0d419d3c-goog