scsi: bsg: fix buffer overflow in scsi_bsg_uring_cmd()

The bounds checking in scsi_bsg_uring_cmd() does not work because
cmd->request_len is a u32 and scmd->cmd_len is a u16.  We check that
scmd->cmd_len is valid but if the cmd->request_len is more than
USHRT_MAX it would still lead to a buffer overflow when we do the
copy_from_user().

Fixes: 7b6d3255e7f8 ("scsi: bsg: add io_uring passthrough handler")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Link: https://patch.msgid.link/adjNnMYK7A7KMNkA@stanley.mountain
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/scsi/scsi_bsg.c b/drivers/scsi/scsi_bsg.c
index c3ce497a3b94fed111c9a7eb7b4043611001dcd6..e80dec53174eac5b09441db092a8348dff32fb2e 100644 (file)
--- a/drivers/scsi/scsi_bsg.c
+++ b/drivers/scsi/scsi_bsg.c
@@ -137,11 +137,11 @@ static int scsi_bsg_uring_cmd(struct request_queue *q, struct io_uring_cmd *iouc
                return PTR_ERR(req);
 
        scmd = blk_mq_rq_to_pdu(req);
-       scmd->cmd_len = cmd->request_len;
-       if (scmd->cmd_len > sizeof(scmd->cmnd)) {
+       if (cmd->request_len > sizeof(scmd->cmnd)) {
                ret = -EINVAL;
                goto out_free_req;
        }
+       scmd->cmd_len = cmd->request_len;
        scmd->allowed = SG_DEFAULT_RETRIES;
 
        if (copy_from_user(scmd->cmnd, uptr64(cmd->request), cmd->request_len)) {