s390/sclp: Prevent release of buffer in I/O

When a task waiting for completion of a Store Data operation is
interrupted, an attempt is made to halt this operation. If this attempt
fails due to a hardware or firmware problem, there is a chance that the
SCLP facility might store data into buffers referenced by the original
operation at a later time.

Handle this situation by not releasing the referenced data buffers if
the halt attempt fails. For current use cases, this might result in a
leak of few pages of memory in case of a rare hardware/firmware
malfunction.

Reviewed-by: Heiko Carstens <[email protected]>
Signed-off-by: Peter Oberparleiter <[email protected]>
Signed-off-by: Alexander Gordeev <[email protected]>

Author: oberpar

drivers/s390/char/sclp_sd.c

@@ -324,8 +324,14 @@ static int sclp_sd_store_data(struct sclp_sd_data *result, u8 di)
 			  &esize);
 	if (rc) {
 		/* Cancel running request if interrupted */
-		if (rc == -ERESTARTSYS)
-			sclp_sd_sync(page, SD_EQ_HALT, di, 0, 0, NULL, NULL);
+		if (rc == -ERESTARTSYS) {
+			if (sclp_sd_sync(page, SD_EQ_HALT, di, 0, 0, NULL, NULL)) {
+				pr_warn("Could not stop Store Data request - leaking at least %zu bytes\n",
+					(size_t)dsize * PAGE_SIZE);
+				data = NULL;
+				asce = 0;
+			}
+		}
 		vfree(data);
 		goto out;
 	}