From 6f63e919fe1e335b8abcb3a28bfd4804a98d875a Mon Sep 17 00:00:00 2001 From: "Cen Zhang (Microsoft)" Date: Thu, 24 Sep 2026 22:44:08 -0400 Subject: [PATCH] wifi: mac80211: fix slab-out-of-bounds read in ieee80211_monitor_select_queue() ieee80211_monitor_select_queue() validates the skb length using skb->len before dereferencing pointers into skb->data to access the 802.11 header. However, skb->len includes data in both the linear head buffer and non-linear fragments/pages. When AF_PACKET sends a packet large enough to become non-linear, the 802.11 header at skb->data + len_rthdr may extend past the linear head buffer even though skb->len appears sufficient. This leads to a slab-out-of-bounds read when accessing hdr->frame_control, as the kernel reads beyond the allocated skb head buffer: BUG: KASAN: slab-out-of-bounds in ieee80211_monitor_select_queue+0x1ed/0x220 syzbot has hit the same issues. Fix this by checking skb_headlen(skb) (which gives the length of the linear data region) instead of skb->len before dereferencing skb->data pointers. This ensures the required bytes are actually present in the linear portion of the skb. Apply the same fix to ieee80211_validate_radiotap_len() which has the same class of bug: it uses skb->len to validate accesses to skb->data, and to the corresponding checks in ieee80211_monitor_start_xmit(): for drivers advertising NETIF_F_SG the skb is not linearized before ndo_start_xmit, so the 802.11 header can be read past the linear buffer there as well. Fixes: cf0277e714a0 ("mac80211: fix skb buffering issue") Fixes: 9b8a74e3482f ("[MAC80211]: Improve sanity checks on injected packets") Reported-by: AutonomousCodeSecurity@microsoft.com Reported-by: syzbot+610e40369bc02181bad0@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=610e40369bc02181bad0 Reported-by: syzbot+878643e0580bc580f883@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=878643e0580bc580f883 Assisted-by: GitHub-Copilot:claude-opus-4.6 Signed-off-by: Cen Zhang (Microsoft) Reviewed-by: Francis Perron Link: https://patch.msgid.link/20260925024408.32143-1-cenzhang@linux.microsoft.com Signed-off-by: Johannes Berg --- net/mac80211/iface.c | 4 ++-- net/mac80211/tx.c | 10 +++++----- 2 files changed, 7 insertions(+), 7 deletions(-) diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c index 889c32fd8de1..88942317fec8 100644 --- a/net/mac80211/iface.c +++ b/net/mac80211/iface.c @@ -998,8 +998,8 @@ static u16 ieee80211_monitor_select_queue(struct net_device *dev, len_rthdr = ieee80211_get_radiotap_len(skb->data); hdr = (struct ieee80211_hdr *)(skb->data + len_rthdr); - if (skb->len < len_rthdr + 2 || - skb->len < len_rthdr + ieee80211_hdrlen(hdr->frame_control)) + if (skb_headlen(skb) < len_rthdr + 2 || + skb_headlen(skb) < len_rthdr + ieee80211_hdrlen(hdr->frame_control)) return 0; /* doesn't matter, frame will be dropped */ return ieee80211_select_queue_80211(sdata, skb, hdr); diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c index b88acb18e04d..d51f810dd2c5 100644 --- a/net/mac80211/tx.c +++ b/net/mac80211/tx.c @@ -2091,7 +2091,7 @@ static bool ieee80211_validate_radiotap_len(struct sk_buff *skb) (struct ieee80211_radiotap_header *)skb->data; /* check for not even having the fixed radiotap header part */ - if (unlikely(skb->len < sizeof(struct ieee80211_radiotap_header))) + if (unlikely(skb_headlen(skb) < sizeof(struct ieee80211_radiotap_header))) return false; /* too short to be possibly valid */ /* is it a header version we can trust to find length from? */ @@ -2099,7 +2099,7 @@ static bool ieee80211_validate_radiotap_len(struct sk_buff *skb) return false; /* only version 0 is supported */ /* does the skb contain enough to deliver on the alleged length? */ - if (unlikely(skb->len < ieee80211_get_radiotap_len(skb->data))) + if (unlikely(skb_headlen(skb) < ieee80211_get_radiotap_len(skb->data))) return false; /* skb too short for claimed rt header extent */ return true; @@ -2388,13 +2388,13 @@ netdev_tx_t ieee80211_monitor_start_xmit(struct sk_buff *skb, skb_set_network_header(skb, len_rthdr); skb_set_transport_header(skb, len_rthdr); - if (skb->len < len_rthdr + 2) + if (skb_headlen(skb) < len_rthdr + 2) goto fail; hdr = (struct ieee80211_hdr *)(skb->data + len_rthdr); hdrlen = ieee80211_hdrlen(hdr->frame_control); - if (skb->len < len_rthdr + hdrlen) + if (skb_headlen(skb) < len_rthdr + hdrlen) goto fail; /* @@ -2402,7 +2402,7 @@ netdev_tx_t ieee80211_monitor_start_xmit(struct sk_buff *skb, * carrying a rfc1042 header */ if (ieee80211_is_data(hdr->frame_control) && - skb->len >= len_rthdr + hdrlen + sizeof(rfc1042_header) + 2) { + skb_headlen(skb) >= len_rthdr + hdrlen + sizeof(rfc1042_header) + 2) { u8 *payload = (u8 *)hdr + hdrlen; if (ether_addr_equal(payload, rfc1042_header))