Patch "bpf: sockmap, updating the sg structure should also update curr" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    bpf: sockmap, updating the sg structure should also update curr

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bpf-sockmap-updating-the-sg-structure-should-also-up.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit f25918361336972575caf2fbee637ec22cb475a8
Author: John Fastabend <john.fastabend@xxxxxxxxx>
Date:   Wed Dec 6 15:27:06 2023 -0800

    bpf: sockmap, updating the sg structure should also update curr
    
    [ Upstream commit bb9aefde5bbaf6c168c77ba635c155b4980c2287 ]
    
    Curr pointer should be updated when the sg structure is shifted.
    
    Fixes: 7246d8ed4dcce ("bpf: helper to pop data from messages")
    Signed-off-by: John Fastabend <john.fastabend@xxxxxxxxx>
    Link: https://lore.kernel.org/r/20231206232706.374377-3-john.fastabend@xxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/core/filter.c b/net/core/filter.c
index d866e1c5970cc..3c4dcdc7217e0 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2219,6 +2219,22 @@ BPF_CALL_2(bpf_msg_cork_bytes, struct sk_msg *, msg, u32, bytes)
 	return 0;
 }
 
+static void sk_msg_reset_curr(struct sk_msg *msg)
+{
+	u32 i = msg->sg.start;
+	u32 len = 0;
+
+	do {
+		len += sk_msg_elem(msg, i)->length;
+		sk_msg_iter_var_next(i);
+		if (len >= msg->sg.size)
+			break;
+	} while (i != msg->sg.end);
+
+	msg->sg.curr = i;
+	msg->sg.copybreak = 0;
+}
+
 static const struct bpf_func_proto bpf_msg_cork_bytes_proto = {
 	.func           = bpf_msg_cork_bytes,
 	.gpl_only       = false,
@@ -2338,6 +2354,7 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
 		      msg->sg.end - shift + NR_MSG_FRAG_IDS :
 		      msg->sg.end - shift;
 out:
+	sk_msg_reset_curr(msg);
 	msg->data = sg_virt(&msg->sg.data[first_sge]) + start - offset;
 	msg->data_end = msg->data + bytes;
 	return 0;
@@ -2471,6 +2488,7 @@ BPF_CALL_4(bpf_msg_push_data, struct sk_msg *, msg, u32, start,
 		msg->sg.data[new] = rsge;
 	}
 
+	sk_msg_reset_curr(msg);
 	sk_msg_compute_data_pointers(msg);
 	return 0;
 }
@@ -2642,6 +2660,7 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
 
 	sk_mem_uncharge(msg->sk, len - pop);
 	msg->sg.size -= (len - pop);
+	sk_msg_reset_curr(msg);
 	sk_msg_compute_data_pointers(msg);
 	return 0;
 }