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SubjectRe: [PATCH v4 3/4] virt/coco/sev-guest: Remove err in handle_guest_request
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On 10/24/22 17:46, Dionna Glaze wrote:
> 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.
>
> The fw_err argument is better to just pass through to
> snp_issue_guest_request, so we do that. Since the issue_request's
> signature has changed fw_err to exitinfo2, we change the argument name
> here.
>
> 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>
>
> Fixes: fce96cf04430 ("virt: Add SEV-SNP guest driver")
> Signed-off-by: Dionna Glaze <dionnaglaze@google.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> ---
> drivers/virt/coco/sev-guest/sev-guest.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
> index f422f9c58ba7..0508c2f46f6b 100644
> --- a/drivers/virt/coco/sev-guest/sev-guest.c
> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
> @@ -303,9 +303,8 @@ static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8
>
> static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
> u8 type, void *req_buf, size_t req_sz, void *resp_buf,
> - u32 resp_sz, __u64 *fw_err)
> + u32 resp_sz, __u64 *exitinfo2)
> {
> - unsigned long err;
> u64 seqno;
> int rc;
>
> @@ -322,9 +321,7 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
> return rc;
>
> /* Call firmware to process the request */
> - rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
> - if (fw_err)
> - *fw_err = err;
> + rc = snp_issue_guest_request(exit_code, &snp_dev->input, exitinfo2);
>
> if (rc)
> return rc;

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