Hello Zhang,
On Tue, 8 Dec 2020 20:45:23 +0800, Xiaohui Zhang <[email protected]> wrote:
> From: Zhang Xiaohui <[email protected]>
>
> mwifiex_config_scan() calls memcpy() without checking
> the destination size may trigger a buffer overflower,
> which a local user could use to cause denial of service
> or the execution of arbitrary code.
> Fix it by putting the length check before calling memcpy().
>
> Signed-off-by: Zhang Xiaohui <[email protected]>
> ---
> drivers/net/wireless/marvell/mwifiex/scan.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/net/wireless/marvell/mwifiex/scan.c b/drivers/net/wireless/marvell/mwifiex/scan.c
> index c2a685f63..b1d90678f 100644
> --- a/drivers/net/wireless/marvell/mwifiex/scan.c
> +++ b/drivers/net/wireless/marvell/mwifiex/scan.c
> @@ -930,6 +930,8 @@ mwifiex_config_scan(struct mwifiex_private *priv,
> "DIRECT-", 7))
> wildcard_ssid_tlv->max_ssid_length = 0xfe;
>
> + if (ssid_len > 1)
> + ssid_len = 1;
Why do your believe the available size is only '1'? A SSID is expected
to be of size IEEE80211_MAX_SSID_LE/32 and the wildcard_ssid_tlv pointer
is casted from tlv_pos (some lines above) which is a pointer/index into
scan_cfg_out->tlv_buf...
And the define (line 44) indicates there should be enough space for a SSID:
42 /* Memory needed to store a max number/size WildCard SSID TLV for a firmware
43 scan */
44 #define WILDCARD_SSID_TLV_MAX_SIZE \
45 (MWIFIEX_MAX_SSID_LIST_LENGTH * \
46 (sizeof(struct mwifiex_ie_types_wildcard_ssid_params) \
47 + IEEE80211_MAX_SSID_LEN))
For sure something to improve here instead of using a confusing 'u8 ssid[1]'
in struct mwifiex_ie_types_wildcard_ssid_params...
Regards,
Peter
> memcpy(wildcard_ssid_tlv->ssid,
> user_scan_in->ssid_list[i].ssid, ssid_len);
>
(Note: this is version 1; there's a later version posted, which does
not have a v2 tag...)
https://lore.kernel.org/linux-wireless/[email protected]/
On Sat, Jan 9, 2021 at 7:11 AM Peter Seiderer <[email protected]> wrote:
> On Tue, 8 Dec 2020 20:45:23 +0800, Xiaohui Zhang <[email protected]> wrote:
> > From: Zhang Xiaohui <[email protected]>
> > mwifiex_config_scan() calls memcpy() without checking
> > the destination size may trigger a buffer overflower,
> > which a local user could use to cause denial of service
> > or the execution of arbitrary code.
> > Fix it by putting the length check before calling memcpy().
> >
> > Signed-off-by: Zhang Xiaohui <[email protected]>
> > ---
> > drivers/net/wireless/marvell/mwifiex/scan.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/net/wireless/marvell/mwifiex/scan.c b/drivers/net/wireless/marvell/mwifiex/scan.c
> > index c2a685f63..b1d90678f 100644
> > --- a/drivers/net/wireless/marvell/mwifiex/scan.c
> > +++ b/drivers/net/wireless/marvell/mwifiex/scan.c
> > @@ -930,6 +930,8 @@ mwifiex_config_scan(struct mwifiex_private *priv,
> > "DIRECT-", 7))
> > wildcard_ssid_tlv->max_ssid_length = 0xfe;
> >
> > + if (ssid_len > 1)
> > + ssid_len = 1;
>
> Why do your believe the available size is only '1'? A SSID is expected
> to be of size IEEE80211_MAX_SSID_LE/32 and the wildcard_ssid_tlv pointer
> is casted from tlv_pos (some lines above) which is a pointer/index into
> scan_cfg_out->tlv_buf...
I pointed out this discrepancy already, taking a slightly different approach:
https://lore.kernel.org/linux-wireless/CA+ASDXPVu5S0Vm0aOcyqLN090u3BwA_nV358YwkpXuU223Ug9g@mail.gmail.com/
> And the define (line 44) indicates there should be enough space for a SSID:
>
> 42 /* Memory needed to store a max number/size WildCard SSID TLV for a firmware
> 43 scan */
> 44 #define WILDCARD_SSID_TLV_MAX_SIZE \
> 45 (MWIFIEX_MAX_SSID_LIST_LENGTH * \
> 46 (sizeof(struct mwifiex_ie_types_wildcard_ssid_params) \
> 47 + IEEE80211_MAX_SSID_LEN))
Ah, good catch. So this may not be a true overflow issue at all, even
if it's confusing and bad code. The "problem" is that this piece of
the struct is variable-length, and unless we're going to dynamically
resize/reallocate the whole buffer, we have to assume the initial
allocation was large enough (and per your note, it is).
> For sure something to improve here instead of using a confusing 'u8 ssid[1]'
> in struct mwifiex_ie_types_wildcard_ssid_params...
Yep.
Brian