FAILED: patch "[PATCH] gso: fix udp gso fraglist segmentation after pull from" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x a1e40ac5b5e9077fe1f7ae0eb88034db0f9ae1ab
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024100726-unlocking-handled-41bb@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

a1e40ac5b5e9 ("gso: fix udp gso fraglist segmentation after pull from frag_list") 9840036786d9 ("gso: fix dodgy bit handling for GSO_UDP_L4") c3df39ac9b0e ("udp: ipv4: manipulate network header of NATed UDP GRO fraglist")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a1e40ac5b5e9077fe1f7ae0eb88034db0f9ae1ab Mon Sep 17 00:00:00 2001
From: Willem de Bruijn <[email protected]>
Date: Tue, 1 Oct 2024 13:17:46 -0400
Subject: [PATCH] gso: fix udp gso fraglist segmentation after pull from
frag_list

Detect gso fraglist skbs with corrupted geometry (see below) and pass these to skb_segment instead of skb_segment_list, as the first can segment them correctly.

Valid SKB_GSO_FRAGLIST skbs
- consist of two or more segments
- the head_skb holds the protocol headers plus first gso_size
- one or more frag_list skbs hold exactly one segment
- all but the last must be gso_size

Optional datapath hooks such as NAT and BPF (bpf_skb_pull_data) can modify these skbs, breaking these invariants.

In extreme cases they pull all data into skb linear. For UDP, this causes a NULL ptr deref in __udpv4_gso_segment_list_csum at udp_hdr(seg->next)->dest.

Detect invalid geometry due to pull, by checking head_skb size. Don't just drop, as this may blackhole a destination. Convert to be able to pass to regular skb_segment.

index d842303587af..a5be6e4ed326 100644
@@ -296,8 +296,26 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
 		return NULL;
 	}
 
-	if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST)
-		return __udp_gso_segment_list(gso_skb, features, is_ipv6);
+	if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST) {
+		 /* Detect modified geometry and pass those to skb_segment. */
+		if (skb_pagelen(gso_skb) - sizeof(*uh) == skb_shinfo(gso_skb)->gso_size)
+			return __udp_gso_segment_list(gso_skb, features, is_ipv6);
+
+		 /* Setup csum, as fraglist skips this in udp4_gro_receive. */
+		gso_skb->csum_start = skb_transport_header(gso_skb) - gso_skb->head;
+		gso_skb->csum_offset = offsetof(struct udphdr, check);
+		gso_skb->ip_summed = CHECKSUM_PARTIAL;
+
+		uh = udp_hdr(gso_skb);
+		if (is_ipv6)
+			uh->check = ~udp_v6_check(gso_skb->len,
+						  &ipv6_hdr(gso_skb)->saddr,
+						  &ipv6_hdr(gso_skb)->daddr, 0);
+		else
+			uh->check = ~udp_v4_check(gso_skb->len,
+						  ip_hdr(gso_skb)->saddr,
+						  ip_hdr(gso_skb)->daddr, 0);
+	}
 
 	skb_pull(gso_skb, sizeof(*uh));