ide-cd: Do not access completed requests in the irq handler

ide_cd_error_cmd() can complete an erroneous request with leftover
buffers. Signal this with its return value so that the request is not
accessed after its completion in the irq handler and we oops.

Cc: <stable@kernel.org> # 32.x 33.x 34.x
Signed-off-by: NBorislav Petkov <bp@alien8.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/ide/ide-cd.c

@@ -506,15 +506,22 @@ int ide_cd_queue_pc(ide_drive_t *drive, const unsigned char *cmd,
 	return (flags & REQ_FAILED) ? -EIO : 0;
 }
 
-static void ide_cd_error_cmd(ide_drive_t *drive, struct ide_cmd *cmd)
+/*
+ * returns true if rq has been completed
+ */
+static bool ide_cd_error_cmd(ide_drive_t *drive, struct ide_cmd *cmd)
 {
 	unsigned int nr_bytes = cmd->nbytes - cmd->nleft;
 
 	if (cmd->tf_flags & IDE_TFLAG_WRITE)
 		nr_bytes -= cmd->last_xfer_len;
 
-	if (nr_bytes > 0)
+	if (nr_bytes > 0) {
 		ide_complete_rq(drive, 0, nr_bytes);
+		return true;
+	}
+
+	return false;
 }
 
 static ide_startstop_t cdrom_newpc_intr(ide_drive_t *drive)
@@ -679,7 +686,8 @@ static ide_startstop_t cdrom_newpc_intr(ide_drive_t *drive)
 		}
 
 		if (uptodate == 0 && rq->bio)
-			ide_cd_error_cmd(drive, cmd);
+			if (ide_cd_error_cmd(drive, cmd))
+				return ide_stopped;
 
 		/* make sure it's fully ended */
 		if (blk_fs_request(rq) == 0) {