Patch "net: allow skb_datagram_iter to be called from any context" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    net: allow skb_datagram_iter to be called from any context

to the 5.15-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:
     net-allow-skb_datagram_iter-to-be-called-from-any-co.patch
and it can be found in the queue-5.15 subdirectory.

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



commit bd0257f05b04b15a8cd634b509e555233e19c01e
Author: Sagi Grimberg <sagi@xxxxxxxxxxx>
Date:   Wed Jun 26 13:00:08 2024 +0300

    net: allow skb_datagram_iter to be called from any context
    
    [ Upstream commit d2d30a376d9cc94c6fb730c58b3e5b7426ecb6de ]
    
    We only use the mapping in a single context, so kmap_local is sufficient
    and cheaper. Make sure to use skb_frag_foreach_page as skb frags may
    contain compound pages and we need to map page by page.
    
    Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
    Closes: https://lore.kernel.org/oe-lkp/202406161539.b5ff7b20-oliver.sang@xxxxxxxxx
    Fixes: 950fcaecd5cc ("datagram: consolidate datagram copy to iter helpers")
    Signed-off-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
    Link: https://patch.msgid.link/20240626100008.831849-1-sagi@xxxxxxxxxxx
    Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/core/datagram.c b/net/core/datagram.c
index 1ff8241217a9c..6b7db06eafe68 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -440,15 +440,22 @@ static int __skb_datagram_iter(const struct sk_buff *skb, int offset,
 
 		end = start + skb_frag_size(frag);
 		if ((copy = end - offset) > 0) {
-			struct page *page = skb_frag_page(frag);
-			u8 *vaddr = kmap(page);
+			u32 p_off, p_len, copied;
+			struct page *p;
+			u8 *vaddr;
 
 			if (copy > len)
 				copy = len;
-			n = INDIRECT_CALL_1(cb, simple_copy_to_iter,
-					vaddr + skb_frag_off(frag) + offset - start,
-					copy, data, to);
-			kunmap(page);
+
+			skb_frag_foreach_page(frag,
+					      skb_frag_off(frag) + offset - start,
+					      copy, p, p_off, p_len, copied) {
+				vaddr = kmap_local_page(p);
+				n = INDIRECT_CALL_1(cb, simple_copy_to_iter,
+					vaddr + p_off, p_len, data, to);
+				kunmap_local(vaddr);
+			}
+
 			offset += n;
 			if (n != copy)
 				goto short_copy;