On 23. 05. 19, 4:38, Gen Zhang wrote: > In sg_write(), the opcode of the command is fetched the first time from > the userspace by __get_user(). Then the whole command, the opcode > included, is fetched again from userspace by __copy_from_user(). > However, a malicious user can change the opcode between the two fetches. > This can cause inconsistent data and potential errors as cmnd is used in > the following codes. > > Thus we should check opcode between the two fetches to prevent this. > > Signed-off-by: Gen Zhang <blackgod016574@xxxxxxxxx> > --- > diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c > index d3f1531..a2971b8 100644 > --- a/drivers/scsi/sg.c > +++ b/drivers/scsi/sg.c > @@ -694,6 +694,8 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos) > hp->flags = input_size; /* structure abuse ... */ > hp->pack_id = old_hdr.pack_id; > hp->usr_ptr = NULL; > + if (opcode != cmnd[0]) > + return -EINVAL; Isn't it too early to check cmnd which is copied only here: > if (__copy_from_user(cmnd, buf, cmd_size)) > return -EFAULT; > /* > --- > thanks, -- js suse labs
