From: Kyle Zeng Date: Sun, 7 Jun 2026 02:18:19 +0000 (-0700) Subject: net: guard timestamp cmsgs to real error queue skbs X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=1ee90b77b727df903033db873c75caac5c27ec98;p=thirdparty%2Flinux.git net: guard timestamp cmsgs to real error queue skbs skb_is_err_queue() treats PACKET_OUTGOING as the sole marker for an skb from sk_error_queue. That assumption is not true for AF_PACKET sockets: outgoing packet taps are also delivered to packet sockets with skb->pkt_type == PACKET_OUTGOING, but their skb->cb is owned by AF_PACKET instead of struct sock_exterr_skb. If such an skb is received with timestamping enabled, the generic timestamp cmsg path can read AF_PACKET control-buffer state as sock_exterr_skb::opt_stats. With SO_RXQ_OVFL enabled, the packet drop counter overlaps opt_stats. An odd drop count makes the path emit SCM_TIMESTAMPING_OPT_STATS with skb->len and skb->data. For non-linear skbs this copies past the linear head and can trigger hardened usercopy or disclose adjacent heap contents. Keep skb_is_err_queue() local to net/socket.c, but make it verify that the PACKET_OUTGOING marker is paired with the sock_rmem_free destructor installed by sock_queue_err_skb(). AF_PACKET receive skbs use normal receive ownership and no longer pass as error-queue skbs, while legitimate sk_error_queue entries keep the PACKET_OUTGOING marker and sock_rmem_free ownership. Fixes: 8605330aac5a ("tcp: fix SCM_TIMESTAMPING_OPT_STATS for normal skbs") Signed-off-by: Kyle Zeng Reviewed-by: Kuniyuki Iwashima Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260607021819.49698-1-kylebot@openai.com Signed-off-by: Jakub Kicinski --- diff --git a/include/net/sock.h b/include/net/sock.h index dccd3738c368..95e157eee8d9 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1856,6 +1856,7 @@ struct sk_buff *sock_omalloc(struct sock *sk, unsigned long size, gfp_t priority); void skb_orphan_partial(struct sk_buff *skb); void sock_rfree(struct sk_buff *skb); +void sock_rmem_free(struct sk_buff *skb); void sock_efree(struct sk_buff *skb); #ifdef CONFIG_INET void sock_edemux(struct sk_buff *skb); diff --git a/net/core/skbuff.c b/net/core/skbuff.c index c02f0a507ba8..8eab8eb5006a 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -5450,7 +5450,7 @@ int skb_cow_data(struct sk_buff *skb, int tailbits, struct sk_buff **trailer) } EXPORT_SYMBOL_GPL(skb_cow_data); -static void sock_rmem_free(struct sk_buff *skb) +void sock_rmem_free(struct sk_buff *skb) { struct sock *sk = skb->sk; @@ -5459,8 +5459,8 @@ static void sock_rmem_free(struct sk_buff *skb) static void skb_set_err_queue(struct sk_buff *skb) { - /* pkt_type of skbs received on local sockets is never PACKET_OUTGOING. - * So, it is safe to (mis)use it to mark skbs on the error queue. + /* The error-queue test in skb_is_err_queue() matches this marker + * with the sock_rmem_free destructor installed by sock_queue_err_skb(). */ skb->pkt_type = PACKET_OUTGOING; BUILD_BUG_ON(PACKET_OUTGOING == 0); diff --git a/net/socket.c b/net/socket.c index 22a412fdec07..c2698a1441a7 100644 --- a/net/socket.c +++ b/net/socket.c @@ -852,12 +852,13 @@ EXPORT_SYMBOL(kernel_sendmsg); static bool skb_is_err_queue(const struct sk_buff *skb) { - /* pkt_type of skbs enqueued on the error queue are set to - * PACKET_OUTGOING in skb_set_err_queue(). This is only safe to do - * in recvmsg, since skbs received on a local socket will never - * have a pkt_type of PACKET_OUTGOING. + /* Error-queue skbs are marked as PACKET_OUTGOING in + * skb_set_err_queue() and use the destructor installed by + * sock_queue_err_skb(). PACKET_OUTGOING alone is not unique: + * AF_PACKET outgoing taps use the same pkt_type. */ - return skb->pkt_type == PACKET_OUTGOING; + return skb->pkt_type == PACKET_OUTGOING && + skb->destructor == sock_rmem_free; } /* On transmit, software and hardware timestamps are returned independently.