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mac80211: make ieee80211_build_preq_ies safer
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Instead of assuming 200 bytes are always enough for
all the IEs we add, give the length of the buffer
to the function and warn instead of overrunning.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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Johannes Berg committed Nov 30, 2012
1 parent f94f8b1 commit c604b9f
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Showing 3 changed files with 41 additions and 17 deletions.
3 changes: 2 additions & 1 deletion net/mac80211/ieee80211_i.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1034,6 +1034,7 @@ struct ieee80211_local {
enum ieee80211_band hw_scan_band;
int scan_channel_idx;
int scan_ies_len;
int hw_scan_ies_bufsize;

struct work_struct sched_scan_stopped_work;
struct ieee80211_sub_if_data __rcu *sched_scan_sdata;
Expand Down Expand Up @@ -1573,7 +1574,7 @@ void ieee80211_send_deauth_disassoc(struct ieee80211_sub_if_data *sdata,
const u8 *bssid, u16 stype, u16 reason,
bool send_frame, u8 *frame_buf);
int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,
const u8 *ie, size_t ie_len,
size_t buffer_len, const u8 *ie, size_t ie_len,
enum ieee80211_band band, u32 rate_mask,
u8 channel);
struct sk_buff *ieee80211_build_probe_req(struct ieee80211_sub_if_data *sdata,
Expand Down
21 changes: 12 additions & 9 deletions net/mac80211/scan.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -247,6 +247,7 @@ static bool ieee80211_prep_hw_scan(struct ieee80211_local *local)
local->hw_scan_req->n_channels = n_chans;

ielen = ieee80211_build_preq_ies(local, (u8 *)local->hw_scan_req->ie,
local->hw_scan_ies_bufsize,
req->ie, req->ie_len, band,
req->rates[band], 0);
local->hw_scan_req->ie_len = ielen;
Expand Down Expand Up @@ -445,11 +446,13 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
if (local->ops->hw_scan) {
u8 *ies;

local->hw_scan_ies_bufsize = 2 + IEEE80211_MAX_SSID_LEN +
local->scan_ies_len +
req->ie_len;
local->hw_scan_req = kmalloc(
sizeof(*local->hw_scan_req) +
req->n_channels * sizeof(req->channels[0]) +
2 + IEEE80211_MAX_SSID_LEN + local->scan_ies_len +
req->ie_len, GFP_KERNEL);
local->hw_scan_ies_bufsize, GFP_KERNEL);
if (!local->hw_scan_req)
return -ENOMEM;

Expand Down Expand Up @@ -928,7 +931,10 @@ int ieee80211_request_sched_scan_start(struct ieee80211_sub_if_data *sdata,
{
struct ieee80211_local *local = sdata->local;
struct ieee80211_sched_scan_ies sched_scan_ies;
int ret, i;
int ret, i, iebufsz;

iebufsz = 2 + IEEE80211_MAX_SSID_LEN +
local->scan_ies_len + req->ie_len;

mutex_lock(&local->mtx);

Expand All @@ -946,19 +952,16 @@ int ieee80211_request_sched_scan_start(struct ieee80211_sub_if_data *sdata,
if (!local->hw.wiphy->bands[i])
continue;

sched_scan_ies.ie[i] = kzalloc(2 + IEEE80211_MAX_SSID_LEN +
local->scan_ies_len +
req->ie_len,
GFP_KERNEL);
sched_scan_ies.ie[i] = kzalloc(iebufsz, GFP_KERNEL);
if (!sched_scan_ies.ie[i]) {
ret = -ENOMEM;
goto out_free;
}

sched_scan_ies.len[i] =
ieee80211_build_preq_ies(local, sched_scan_ies.ie[i],
req->ie, req->ie_len, i,
(u32) -1, 0);
iebufsz, req->ie, req->ie_len,
i, (u32) -1, 0);
}

ret = drv_sched_scan_start(local, sdata, req, &sched_scan_ies);
Expand Down
34 changes: 27 additions & 7 deletions net/mac80211/util.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1107,12 +1107,12 @@ void ieee80211_send_deauth_disassoc(struct ieee80211_sub_if_data *sdata,
}

int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,
const u8 *ie, size_t ie_len,
size_t buffer_len, const u8 *ie, size_t ie_len,
enum ieee80211_band band, u32 rate_mask,
u8 channel)
{
struct ieee80211_supported_band *sband;
u8 *pos;
u8 *pos = buffer, *end = buffer + buffer_len;
size_t offset = 0, noffset;
int supp_rates_len, i;
u8 rates[32];
Expand All @@ -1123,8 +1123,6 @@ int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,
if (WARN_ON_ONCE(!sband))
return 0;

pos = buffer;

num_rates = 0;
for (i = 0; i < sband->n_bitrates; i++) {
if ((BIT(i) & rate_mask) == 0)
Expand All @@ -1134,6 +1132,8 @@ int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,

supp_rates_len = min_t(int, num_rates, 8);

if (end - pos < 2 + supp_rates_len)
goto out_err;
*pos++ = WLAN_EID_SUPP_RATES;
*pos++ = supp_rates_len;
memcpy(pos, rates, supp_rates_len);
Expand All @@ -1150,20 +1150,26 @@ int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,
before_extrates,
ARRAY_SIZE(before_extrates),
offset);
if (end - pos < noffset - offset)
goto out_err;
memcpy(pos, ie + offset, noffset - offset);
pos += noffset - offset;
offset = noffset;
}

ext_rates_len = num_rates - supp_rates_len;
if (ext_rates_len > 0) {
if (end - pos < 2 + ext_rates_len)
goto out_err;
*pos++ = WLAN_EID_EXT_SUPP_RATES;
*pos++ = ext_rates_len;
memcpy(pos, rates + supp_rates_len, ext_rates_len);
pos += ext_rates_len;
}

if (channel && sband->band == IEEE80211_BAND_2GHZ) {
if (end - pos < 3)
goto out_err;
*pos++ = WLAN_EID_DS_PARAMS;
*pos++ = 1;
*pos++ = channel;
Expand All @@ -1182,14 +1188,19 @@ int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,
noffset = ieee80211_ie_split(ie, ie_len,
before_ht, ARRAY_SIZE(before_ht),
offset);
if (end - pos < noffset - offset)
goto out_err;
memcpy(pos, ie + offset, noffset - offset);
pos += noffset - offset;
offset = noffset;
}

if (sband->ht_cap.ht_supported)
if (sband->ht_cap.ht_supported) {
if (end - pos < 2 + sizeof(struct ieee80211_ht_cap))
goto out_err;
pos = ieee80211_ie_build_ht_cap(pos, &sband->ht_cap,
sband->ht_cap.cap);
}

/*
* If adding more here, adjust code in main.c
Expand All @@ -1199,14 +1210,22 @@ int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,
/* add any remaining custom IEs */
if (ie && ie_len) {
noffset = ie_len;
if (end - pos < noffset - offset)
goto out_err;
memcpy(pos, ie + offset, noffset - offset);
pos += noffset - offset;
}

if (sband->vht_cap.vht_supported)
if (sband->vht_cap.vht_supported) {
if (end - pos < 2 + sizeof(struct ieee80211_vht_cap))
goto out_err;
pos = ieee80211_ie_build_vht_cap(pos, &sband->vht_cap,
sband->vht_cap.cap);
}

return pos - buffer;
out_err:
WARN_ONCE(1, "not enough space for preq IEs\n");
return pos - buffer;
}

Expand Down Expand Up @@ -1239,7 +1258,8 @@ struct sk_buff *ieee80211_build_probe_req(struct ieee80211_sub_if_data *sdata,
else
chan_no = ieee80211_frequency_to_channel(chan->center_freq);

buf_len = ieee80211_build_preq_ies(local, buf, ie, ie_len, chan->band,
buf_len = ieee80211_build_preq_ies(local, buf, 200 + ie_len,
ie, ie_len, chan->band,
ratemask, chan_no);

skb = ieee80211_probereq_get(&local->hw, &sdata->vif,
Expand Down

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