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skb_expand_head() adjust skb->truesize incorrectly

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Christoph Paasch reports [1] about incorrect skb->truesize
after skb_expand_head() call in ip6_xmit.
This may happen because of two reasons:
- skb_set_owner_w() for newly cloned skb is called too early,
before pskb_expand_head() where truesize is adjusted for (!skb-sk) case.
- pskb_expand_head() does not adjust truesize in (skb->sk) case.
In this case sk->sk_wmem_alloc should be adjusted too.

[1] https://lkml.org/lkml/2021/8/20/1082

Fixes: f1260ff15a ("skbuff: introduce skb_expand_head()")
Fixes: 2d85a1b31d ("ipv6: ip6_finish_output2: set sk into newly allocated nskb")
Reported-by: Christoph Paasch <christoph.paasch@gmail.com>
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/644330dd-477e-0462-83bf-9f514c41edd1@virtuozzo.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Vasily Averin 2021-10-22 13:28:37 +03:00 committed by Jakub Kicinski
parent 7fcb1c950e
commit 7f678def99
2 changed files with 35 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
net/core/skbuff.c
View File

@ -80,6 +80,7 @@
#include <linux/indirect_call_wrapper.h>
#include "datagram.h"
#include "sock_destructor.h"
struct kmem_cache *skbuff_head_cache __ro_after_init;
static struct kmem_cache *skbuff_fclone_cache __ro_after_init;
@ -1804,30 +1805,39 @@ EXPORT_SYMBOL(skb_realloc_headroom);
struct sk_buff *skb_expand_head(struct sk_buff *skb, unsigned int headroom)
{
int delta = headroom - skb_headroom(skb);
int osize = skb_end_offset(skb);
struct sock *sk = skb->sk;
if (WARN_ONCE(delta <= 0,
"%s is expecting an increase in the headroom", __func__))
return skb;
/* pskb_expand_head() might crash, if skb is shared */
if (skb_shared(skb)) {
delta = SKB_DATA_ALIGN(delta);
/* pskb_expand_head() might crash, if skb is shared. */
if (skb_shared(skb) || !is_skb_wmem(skb)) {
struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
if (likely(nskb)) {
if (skb->sk)
skb_set_owner_w(nskb, skb->sk);
consume_skb(skb);
} else {
kfree_skb(skb);
}
if (unlikely(!nskb))
goto fail;
if (sk)
skb_set_owner_w(nskb, sk);
consume_skb(skb);
skb = nskb;
}
if (skb &&
pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) {
kfree_skb(skb);
skb = NULL;
if (pskb_expand_head(skb, delta, 0, GFP_ATOMIC))
goto fail;
if (sk && is_skb_wmem(skb)) {
delta = skb_end_offset(skb) - osize;
refcount_add(delta, &sk->sk_wmem_alloc);
skb->truesize += delta;
}
return skb;
fail:
kfree_skb(skb);
return NULL;
}
EXPORT_SYMBOL(skb_expand_head);

12
net/core/sock_destructor.h Normal file
View File

@ -0,0 +1,12 @@
/* SPDX-License-Identifier: GPL-2.0-or-later */
#ifndef _NET_CORE_SOCK_DESTRUCTOR_H
#define _NET_CORE_SOCK_DESTRUCTOR_H
#include <net/tcp.h>
static inline bool is_skb_wmem(const struct sk_buff *skb)
{
return skb->destructor == sock_wfree ||
skb->destructor == __sock_wfree ||
(IS_ENABLED(CONFIG_INET) && skb->destructor == tcp_wfree);
}
#endif