From: Eric Dumazet Date: Fri, 21 Nov 2025 15:41:00 +0000 (+0000) Subject: net: sched: fix TCF_LAYER_TRANSPORT handling in tcf_get_base_ptr() X-Git-Tag: v6.18~19^2~23 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4fe5a00ec70717a7f1002d8913ec6143582b3c8e;p=thirdparty%2Flinux.git net: sched: fix TCF_LAYER_TRANSPORT handling in tcf_get_base_ptr() syzbot reported that tcf_get_base_ptr() can be called while transport header is not set [1]. Instead of returning a dangling pointer, return NULL. Fix tcf_get_base_ptr() callers to handle this NULL value. [1] WARNING: CPU: 1 PID: 6019 at ./include/linux/skbuff.h:3071 skb_transport_header include/linux/skbuff.h:3071 [inline] WARNING: CPU: 1 PID: 6019 at ./include/linux/skbuff.h:3071 tcf_get_base_ptr include/net/pkt_cls.h:539 [inline] WARNING: CPU: 1 PID: 6019 at ./include/linux/skbuff.h:3071 em_nbyte_match+0x2d8/0x3f0 net/sched/em_nbyte.c:43 Modules linked in: CPU: 1 UID: 0 PID: 6019 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Call Trace: tcf_em_match net/sched/ematch.c:494 [inline] __tcf_em_tree_match+0x1ac/0x770 net/sched/ematch.c:520 tcf_em_tree_match include/net/pkt_cls.h:512 [inline] basic_classify+0x115/0x2d0 net/sched/cls_basic.c:50 tc_classify include/net/tc_wrapper.h:197 [inline] __tcf_classify net/sched/cls_api.c:1764 [inline] tcf_classify+0x4cf/0x1140 net/sched/cls_api.c:1860 multiq_classify net/sched/sch_multiq.c:39 [inline] multiq_enqueue+0xfd/0x4c0 net/sched/sch_multiq.c:66 dev_qdisc_enqueue+0x4e/0x260 net/core/dev.c:4118 __dev_xmit_skb net/core/dev.c:4214 [inline] __dev_queue_xmit+0xe83/0x3b50 net/core/dev.c:4729 packet_snd net/packet/af_packet.c:3076 [inline] packet_sendmsg+0x3e33/0x5080 net/packet/af_packet.c:3108 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg+0x21c/0x270 net/socket.c:742 ____sys_sendmsg+0x505/0x830 net/socket.c:2630 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+f3a497f02c389d86ef16@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/6920855a.a70a0220.2ea503.0058.GAE@google.com/T/#u Signed-off-by: Eric Dumazet Reviewed-by: Jamal Hadi Salim Link: https://patch.msgid.link/20251121154100.1616228-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h index c64fd896b1f9..99ac747b7906 100644 --- a/include/net/pkt_cls.h +++ b/include/net/pkt_cls.h @@ -536,6 +536,8 @@ static inline unsigned char * tcf_get_base_ptr(struct sk_buff *skb, int layer) case TCF_LAYER_NETWORK: return skb_network_header(skb); case TCF_LAYER_TRANSPORT: + if (!skb_transport_header_was_set(skb)) + break; return skb_transport_header(skb); } diff --git a/net/sched/em_cmp.c b/net/sched/em_cmp.c index 64b637f18bc7..48c1bce74f49 100644 --- a/net/sched/em_cmp.c +++ b/net/sched/em_cmp.c @@ -22,9 +22,12 @@ static int em_cmp_match(struct sk_buff *skb, struct tcf_ematch *em, struct tcf_pkt_info *info) { struct tcf_em_cmp *cmp = (struct tcf_em_cmp *) em->data; - unsigned char *ptr = tcf_get_base_ptr(skb, cmp->layer) + cmp->off; + unsigned char *ptr = tcf_get_base_ptr(skb, cmp->layer); u32 val = 0; + if (!ptr) + return 0; + ptr += cmp->off; if (!tcf_valid_offset(skb, ptr, cmp->align)) return 0; diff --git a/net/sched/em_nbyte.c b/net/sched/em_nbyte.c index 4f9f21a05d5e..c65ffa5fff94 100644 --- a/net/sched/em_nbyte.c +++ b/net/sched/em_nbyte.c @@ -42,6 +42,8 @@ static int em_nbyte_match(struct sk_buff *skb, struct tcf_ematch *em, struct nbyte_data *nbyte = (struct nbyte_data *) em->data; unsigned char *ptr = tcf_get_base_ptr(skb, nbyte->hdr.layer); + if (!ptr) + return 0; ptr += nbyte->hdr.off; if (!tcf_valid_offset(skb, ptr, nbyte->hdr.len)) diff --git a/net/sched/em_text.c b/net/sched/em_text.c index 6b3d0af72c39..692e2be1793e 100644 --- a/net/sched/em_text.c +++ b/net/sched/em_text.c @@ -29,12 +29,19 @@ static int em_text_match(struct sk_buff *skb, struct tcf_ematch *m, struct tcf_pkt_info *info) { struct text_match *tm = EM_TEXT_PRIV(m); + unsigned char *ptr; int from, to; - from = tcf_get_base_ptr(skb, tm->from_layer) - skb->data; + ptr = tcf_get_base_ptr(skb, tm->from_layer); + if (!ptr) + return 0; + from = ptr - skb->data; from += tm->from_offset; - to = tcf_get_base_ptr(skb, tm->to_layer) - skb->data; + ptr = tcf_get_base_ptr(skb, tm->to_layer); + if (!ptr) + return 0; + to = ptr - skb->data; to += tm->to_offset; return skb_find_text(skb, from, to, tm->config) != UINT_MAX;