Commit ca9f9cdc authored by Jason Baron's avatar Jason Baron Committed by Jakub Kicinski
Browse files

net: allow alloc_skb_with_frags() to use MAX_SKB_FRAGS 



Currently, alloc_skb_with_frags() will only fill (MAX_SKB_FRAGS - 1)
slots. I think it should use all MAX_SKB_FRAGS slots, as callers of
alloc_skb_with_frags() will size their allocation of frags based
on MAX_SKB_FRAGS.

This issue was discovered via a test patch that sets 'order' to 0
in alloc_skb_with_frags(), which effectively tests/simulates high
fragmentation. In this case sendmsg() on unix sockets will fail every
time for large allocations. If the PAGE_SIZE is 4K, then data_len will
request 68K or 17 pages, but alloc_skb_with_frags() can only allocate
64K in this case or 16 pages.

Fixes: 09c2c907 ("net: allow alloc_skb_with_frags() to allocate bigger packets")
Signed-off-by: default avatarJason Baron <jbaron@akamai.com>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250922191957.2855612-1-jbaron@akamai.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 16d93558

net/core/skbuff.c

+1 −1
Original line number Diff line number Diff line
@@ -6667,7 +6667,7 @@ struct sk_buff *alloc_skb_with_frags(unsigned long header_len, 
		return NULL;



	while (data_len) {

		if (nr_frags == MAX_SKB_FRAGS - 1)

		if (nr_frags == MAX_SKB_FRAGS)

			goto failure;

		while (order && PAGE_ALIGN(data_len) < (PAGE_SIZE << order))

			order--;