[PATCH v3 1/2] virt: tdx-guest: Fix timeout detection in wait_for_quote_completion()

[Moe Mahhouk via B4 Relay]

From: Moe Mahhouk <moe@xxxxxxxxxxxxx>

wait_for_quote_completion() counts the seconds it has waited in i and
reports a timeout when i == timeout. That gets both outcomes of the
last second wrong:

- If the request is still in flight after the last sleep, the loop
  condition increments i once more before it fails, so the loop ends
  with i == timeout + 1 and the function returns 0. The caller then
  returns -EIO instead of -ETIMEDOUT, without the "GetQuote request
  timedout" message. Before commit 0f409eaea53e ("virt: tdx-guest:
  Return error for GetQuote failures") a timed-out request even
  returned success with an empty Quote.

- If the VMM completes the request during the last sleep, the loop ends
  on the status check with i == timeout, and the function returns
  -ETIMEDOUT for a completed request, discarding the Quote.

Decide on the Quote buffer instead: the request timed out if it is
still in flight when the wait ends.

Fixes: f4738f56d1dc ("virt: tdx-guest: Add Quote generation support using TSM_REPORTS")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Kiryl Shutsemau <kas@xxxxxxxxxx>
Closes: https://lore.kernel.org/all/atoHWgQF-0vlTRK4@thinkstation/
Reviewed-by: Kiryl Shutsemau (Meta) <kas@xxxxxxxxxx>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
Signed-off-by: Moe Mahhouk <moe@xxxxxxxxxxxxx>
---
 drivers/virt/coco/tdx-guest/tdx-guest.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/virt/coco/tdx-guest/tdx-guest.c b/drivers/virt/coco/tdx-guest/tdx-guest.c
index 11d741da3b35..a5a53174f9d9 100644
--- a/drivers/virt/coco/tdx-guest/tdx-guest.c
+++ b/drivers/virt/coco/tdx-guest/tdx-guest.c
@@ -282,7 +282,7 @@ static int wait_for_quote_completion(struct tdx_quote_buf *buf, u32 timeout)
 			return -EINTR;
 	}
 
-	return (i == timeout) ? -ETIMEDOUT : 0;
+	return (buf->status == GET_QUOTE_IN_FLIGHT) ? -ETIMEDOUT : 0;
 }
 
 static int tdx_report_new_locked(struct tsm_report *report)

-- 
2.34.1