[PATCH 12/32] cfg80211: Use mem_to_flex_dup() with struct cfg80211_bss_ies

Kees Cook
2022-05-04T01:49:27Z

As part of the work to perform bounds checking on all memcpy() uses,
replace the open-coded a deserialization of bytes out of memory into a
trailing flexible array by using a flex_array.h helper to perform the
allocation, bounds checking, and copying.

Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
include/net/cfg80211.h | 4 ++--
net/wireless/scan.c | 21 ++++++---------------
2 files changed, 8 insertions(+), 17 deletions(-)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 68713388b617..fa236015f6ef 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -2600,9 +2600,9 @@ struct cfg80211_inform_bss {
struct cfg80211_bss_ies {
u64 tsf;
struct rcu_head rcu_head;
- int len;
+ DECLARE_FLEX_ARRAY_ELEMENTS_COUNT(int, len);
bool from_beacon;
- u8 data[];
+ DECLARE_FLEX_ARRAY_ELEMENTS(u8, data);
};

/**
diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index 4a6d86432910..9f53d05c6aaa 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -1932,7 +1932,7 @@ cfg80211_inform_single_bss_data(struct wiphy *wiphy,
gfp_t gfp)
{
struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
- struct cfg80211_bss_ies *ies;
+ struct cfg80211_bss_ies *ies = NULL;
struct ieee80211_channel *channel;
struct cfg80211_internal_bss tmp = {}, *res;
int bss_type;
@@ -1978,13 +1978,10 @@ cfg80211_inform_single_bss_data(struct wiphy *wiphy,
* override the IEs pointer should we have received an earlier
* indication of Probe Response data.
*/
- ies = kzalloc(sizeof(*ies) + ielen, gfp);
- if (!ies)
+ if (mem_to_flex_dup(&ies, ie, ielen, gfp))
return NULL;
- ies->len = ielen;
ies->tsf = tsf;
ies->from_beacon = false;
- memcpy(ies->data, ie, ielen);

switch (ftype) {
case CFG80211_BSS_FTYPE_BEACON:
@@ -2277,7 +2274,7 @@ cfg80211_update_notlisted_nontrans(struct wiphy *wiphy,
size_t ielen = len - offsetof(struct ieee80211_mgmt,
u.probe_resp.variable);
size_t new_ie_len;
- struct cfg80211_bss_ies *new_ies;
+ struct cfg80211_bss_ies *new_ies = NULL;
const struct cfg80211_bss_ies *old;
u8 cpy_len;

@@ -2314,8 +2311,7 @@ cfg80211_update_notlisted_nontrans(struct wiphy *wiphy,
if (!new_ie)
return;

- new_ies = kzalloc(sizeof(*new_ies) + new_ie_len, GFP_ATOMIC);
- if (!new_ies)
+ if (mem_to_flex_dup(&new_ies, new_ie, new_ie_len, GFP_ATOMIC))
goto out_free;

pos = new_ie;
@@ -2333,10 +2329,8 @@ cfg80211_update_notlisted_nontrans(struct wiphy *wiphy,
memcpy(pos, mbssid + cpy_len, ((ie + ielen) - (mbssid + cpy_len)));

/* update ie */
- new_ies->len = new_ie_len;
new_ies->tsf = le64_to_cpu(mgmt->u.probe_resp.timestamp);
new_ies->from_beacon = ieee80211_is_beacon(mgmt->frame_control);
- memcpy(new_ies->data, new_ie, new_ie_len);
if (ieee80211_is_probe_resp(mgmt->frame_control)) {
old = rcu_access_pointer(nontrans_bss->proberesp_ies);
rcu_assign_pointer(nontrans_bss->proberesp_ies, new_ies);
@@ -2363,7 +2357,7 @@ cfg80211_inform_single_bss_frame_data(struct wiphy *wiphy,
gfp_t gfp)
{
struct cfg80211_internal_bss tmp = {}, *res;
- struct cfg80211_bss_ies *ies;
+ struct cfg80211_bss_ies *ies = NULL;
struct ieee80211_channel *channel;
bool signal_valid;
struct ieee80211_ext *ext = NULL;
@@ -2442,14 +2436,11 @@ cfg80211_inform_single_bss_frame_data(struct wiphy *wiphy,
capability = le16_to_cpu(mgmt->u.probe_resp.capab_info);
}

- ies = kzalloc(sizeof(*ies) + ielen, gfp);
- if (!ies)
+ if (mem_to_flex_dup(&ies, variable, ielen, gfp))
return NULL;
- ies->len = ielen;
ies->tsf = le64_to_cpu(mgmt->u.probe_resp.timestamp);
ies->from_beacon = ieee80211_is_beacon(mgmt->frame_control) ||
ieee80211_is_s1g_beacon(mgmt->frame_control);
- memcpy(ies->data, variable, ielen);

if (ieee80211_is_probe_resp(mgmt->frame_control))
rcu_assign_pointer(tmp.pub.proberesp_ies, ies);
--
2.32.0