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tcp: fix skb_copy_ubufs() vs BIG TCP

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David Ahern reported crashes in skb_copy_ubufs() caused by TCP tx zerocopy
using hugepages, and skb length bigger than ~68 KB.

skb_copy_ubufs() assumed it could copy all payload using up to
MAX_SKB_FRAGS order-0 pages.

This assumption broke when BIG TCP was able to put up to 512 KB per skb.

We did not hit this bug at Google because we use CONFIG_MAX_SKB_FRAGS=45
and limit gso_max_size to 180000.

A solution is to use higher order pages if needed.

v2: add missing __GFP_COMP, or we leak memory.

Fixes: 7c4e983c4f ("net: allow gso_max_size to exceed 65536")
Reported-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/netdev/c70000f6-baa4-4a05-46d0-4b3e0dc1ccc8@gmail.com/T/
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Xin Long <lucien.xin@gmail.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Coco Li <lixiaoyan@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2023-04-28 04:32:31 +00:00 committed by David S. Miller
parent 6f75cd166a
commit 7e692df393
1 changed files with 14 additions and 6 deletions
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20
net/core/skbuff.c
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@ -1758,7 +1758,7 @@ int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask)
{
int num_frags = skb_shinfo(skb)->nr_frags;
struct page *page, *head = NULL;
int i, new_frags;
int i, order, psize, new_frags;
u32 d_off;
if (skb_shared(skb) || skb_unclone(skb, gfp_mask))
@ -1767,9 +1767,17 @@ int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask)
if (!num_frags)
goto release;
new_frags = (__skb_pagelen(skb) + PAGE_SIZE - 1) >> PAGE_SHIFT;
/* We might have to allocate high order pages, so compute what minimum
* page order is needed.
*/
order = 0;
while ((PAGE_SIZE << order) * MAX_SKB_FRAGS < __skb_pagelen(skb))
order++;
psize = (PAGE_SIZE << order);
new_frags = (__skb_pagelen(skb) + psize - 1) >> (PAGE_SHIFT + order);
for (i = 0; i < new_frags; i++) {
page = alloc_page(gfp_mask);
page = alloc_pages(gfp_mask | __GFP_COMP, order);
if (!page) {
while (head) {
struct page *next = (struct page *)page_private(head);
@ -1796,11 +1804,11 @@ int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask)
vaddr = kmap_atomic(p);
while (done < p_len) {
if (d_off == PAGE_SIZE) {
if (d_off == psize) {
d_off = 0;
page = (struct page *)page_private(page);
}
copy = min_t(u32, PAGE_SIZE - d_off, p_len - done);
copy = min_t(u32, psize - d_off, p_len - done);
memcpy(page_address(page) + d_off,
vaddr + p_off + done, copy);
done += copy;
@ -1816,7 +1824,7 @@ int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask)
/* skb frags point to kernel buffers */
for (i = 0; i < new_frags - 1; i++) {
__skb_fill_page_desc(skb, i, head, 0, PAGE_SIZE);
__skb_fill_page_desc(skb, i, head, 0, psize);
head = (struct page *)page_private(head);
}
__skb_fill_page_desc(skb, new_frags - 1, head, 0, d_off);