On Fri, Oct 26, 2012 at 4:00 AM, Johannes Berg
<johannes@xxxxxxxxxxxxxxxx> wrote:
> From: Johannes Berg <johannes.berg@xxxxxxxxx>
>
> A number of places in the mesh code don't check that
> the frame data is present and in the skb header when
> trying to access. Add those checks and the necessary
> pskb_may_pull() calls. This prevents accessing data
> that doesn't actually exist.
>
> To do this, export ieee80211_get_mesh_hdrlen() to be
> able to use it in mac80211.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
> ---
> include/net/cfg80211.h | 9 +++++++++
> net/mac80211/rx.c | 32 +++++++++++++++++++++++++++++++-
> net/wireless/util.c | 3 ++-
> 3 files changed, 42 insertions(+), 2 deletions(-)
>
> diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
> index f8cd4cf..7d5b600 100644
> --- a/include/net/cfg80211.h
> +++ b/include/net/cfg80211.h
> @@ -2652,6 +2652,15 @@ unsigned int ieee80211_get_hdrlen_from_skb(const struct sk_buff *skb);
> unsigned int __attribute_const__ ieee80211_hdrlen(__le16 fc);
>
> /**
> + * ieee80211_get_mesh_hdrlen - get mesh extension header length
> + * @meshhdr: the mesh extension header, only the flags field
> + * (first byte) will be accessed
> + * Returns the length of the extension header, which is always at
> + * least 6 bytes and at most 18 if address 5 and 6 are present.
> + */
> +unsigned int ieee80211_get_mesh_hdrlen(struct ieee80211s_hdr *meshhdr);
> +
> +/**
> * DOC: Data path helpers
> *
> * In addition to generic utilities, cfg80211 also offers
> diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
> index 99cdee1..265a032d 100644
> --- a/net/mac80211/rx.c
> +++ b/net/mac80211/rx.c
> @@ -531,6 +531,11 @@ ieee80211_rx_mesh_check(struct ieee80211_rx_data *rx)
>
> if (ieee80211_is_action(hdr->frame_control)) {
> u8 category;
> +
> + /* make sure category field is present */
> + if (rx->skb->len < IEEE80211_MIN_ACTION_SIZE)
> + return RX_DROP_MONITOR;
> +
> mgmt = (struct ieee80211_mgmt *)hdr;
> category = mgmt->u.action.category;
> if (category != WLAN_CATEGORY_MESH_ACTION &&
> @@ -1892,6 +1897,20 @@ ieee80211_rx_h_mesh_fwding(struct ieee80211_rx_data *rx)
>
> hdr = (struct ieee80211_hdr *) skb->data;
> hdrlen = ieee80211_hdrlen(hdr->frame_control);
> +
> + /* make sure fixed part of mesh header is there, also checks skb len */
> + if (!pskb_may_pull(rx->skb, hdrlen + 6))
> + return RX_DROP_MONITOR;
> +
> + mesh_hdr = (struct ieee80211s_hdr *) (skb->data + hdrlen);
> +
> + /* make sure full mesh header is there, also checks skb len */
> + if (!pskb_may_pull(rx->skb,
> + hdrlen + ieee80211_get_mesh_hdrlen(mesh_hdr)))
> + return RX_DROP_MONITOR;
> +
> + /* reload pointers */
> + hdr = (struct ieee80211_hdr *) skb->data;
> mesh_hdr = (struct ieee80211s_hdr *) (skb->data + hdrlen);
>
> /* frame is in RMC, don't forward */
> @@ -1915,9 +1934,12 @@ ieee80211_rx_h_mesh_fwding(struct ieee80211_rx_data *rx)
> if (is_multicast_ether_addr(hdr->addr1)) {
> mpp_addr = hdr->addr3;
> proxied_addr = mesh_hdr->eaddr1;
> - } else {
> + } else if (mesh_hdr->flags & MESH_FLAGS_AE_A5_A6) {
OK, but now the first check (is_multicast_ether_addr()) implies AE_A4
flag. It seems cleaner to just be explicit about what you're asking
for both cases.
> + /* has_a4 already checked in ieee80211_rx_mesh_check */
> mpp_addr = hdr->addr4;
> proxied_addr = mesh_hdr->eaddr2;
> + } else {
> + return RX_DROP_MONITOR;
> }
>
> rcu_read_lock();
> @@ -2354,6 +2376,10 @@ ieee80211_rx_h_action(struct ieee80211_rx_data *rx)
> }
> break;
> case WLAN_CATEGORY_SELF_PROTECTED:
> + if (len < (IEEE80211_MIN_ACTION_SIZE +
> + sizeof(mgmt->u.action.u.self_prot.action_code)))
> + break;
> +
> switch (mgmt->u.action.u.self_prot.action_code) {
> case WLAN_SP_MESH_PEERING_OPEN:
> case WLAN_SP_MESH_PEERING_CLOSE:
> @@ -2372,6 +2398,10 @@ ieee80211_rx_h_action(struct ieee80211_rx_data *rx)
> }
> break;
> case WLAN_CATEGORY_MESH_ACTION:
> + if (len < (IEEE80211_MIN_ACTION_SIZE +
> + sizeof(mgmt->u.action.u.mesh_action.action_code)))
> + break;
> +
> if (!ieee80211_vif_is_mesh(&sdata->vif))
> break;
> if (mesh_action_is_path_sel(mgmt) &&
> diff --git a/net/wireless/util.c b/net/wireless/util.c
> index 45a09de..2762e83 100644
> --- a/net/wireless/util.c
> +++ b/net/wireless/util.c
> @@ -309,7 +309,7 @@ unsigned int ieee80211_get_hdrlen_from_skb(const struct sk_buff *skb)
> }
> EXPORT_SYMBOL(ieee80211_get_hdrlen_from_skb);
>
> -static int ieee80211_get_mesh_hdrlen(struct ieee80211s_hdr *meshhdr)
> +unsigned int ieee80211_get_mesh_hdrlen(struct ieee80211s_hdr *meshhdr)
> {
> int ae = meshhdr->flags & MESH_FLAGS_AE;
> /* 802.11-2012, 8.2.4.7.3 */
> @@ -323,6 +323,7 @@ static int ieee80211_get_mesh_hdrlen(struct ieee80211s_hdr *meshhdr)
> return 18;
> }
> }
> +EXPORT_SYMBOL(ieee80211_get_mesh_hdrlen);
>
> int ieee80211_data_to_8023(struct sk_buff *skb, const u8 *addr,
> enum nl80211_iftype iftype)
> --
> 1.7.10.4
>
>
>
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