On Fri, Sep 10, 2021 at 10:19:03PM +0530, Saurav Girepunje wrote:
>
>
> On 10/09/21 2:30 pm, Dan Carpenter wrote:
> >
> > On Fri, Sep 10, 2021 at 01:59:19PM +0530, Saurav Girepunje wrote:
> > > In rtl8712_cmd.c function read_macreg_hdl,write_macreg_hdl,write_bbreg_hdl
> > > and write_rfreg_hdl all are having same execution.
> >
> > I get what you're trying to do, because this code is bad and duplicative
> > but this is not the right fix.
> >
> > Let's take read_macreg_hdl() as an example.
> >
> > Look at how it's called:
> >
> > 215 switch (pcmd->cmdcode) {
> > 216 case GEN_CMD_CODE(_Read_MACREG):
> > 217 read_macreg_hdl(padapter, (u8 *)pcmd);
> > 218 pcmd_r = pcmd;
> > 219 break;
> >
> > Then look at how it's implemented:
> >
> > 120 static u8 read_macreg_hdl(struct _adapter *padapter, u8 *pbuf)
> > 121 {
> > 122 void (*pcmd_callback)(struct _adapter *dev, struct cmd_obj *pcmd);
> > 123 struct cmd_obj *pcmd = (struct cmd_obj *)pbuf;
> > 124
> > 125 /* invoke cmd->callback function */
> > 126 pcmd_callback = cmd_callback[pcmd->cmdcode].callback;
> >
> > So pcmd->cmdcode is GEN_CMD_CODE(_Read_MACREG). We look that up in the
> > cmd_callback[] array and it is:
> >
> > {GEN_CMD_CODE(_Read_MACREG), NULL}, /*0*/
> >
> > 127 if (!pcmd_callback)
> > 128 r8712_free_cmd_obj(pcmd);
> >
> > So now we no that "pcmd_callback" is NULL meaning it will free "pcmd".
> > And if you remember in the caller it does "pcmd_r = pcmd;" but "pcmd"
> > is freed so that's going to lead to a use after free in r8712_cmd_thread().
> > It's garbage and the patch doesn't really help.
>
> One more thought here after the
>
> 127 if (!pcmd_callback)
> 128 r8712_free_cmd_obj(pcmd);
>
> r8712_free_cmd_obj(pcmd); we could do pcmd = NULL; so in the caller when it
> will do "pcmd_r = pcmd;" it is actually making NULL to pcmd_r. On
> r8712_cmd_thread there is check for pcmd is NULL or not before execution on
> pcmd.
>
> pcmd = cmd_hdl_filter(padapter, pcmd);
> if (pcmd) { /* if pcmd != NULL, cmd will be handled by f/w */
>
> Please let me know you thought on this dan.
You have to look at how it's allocated and is this even called? I
haven't looked so I don't know the answers.
regards,
dan carpenter
