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skb_expand_head() adjust skb->truesize incorrectly

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commit 7f678def99d29c520418607509bb19c7fc96a6db upstream.

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: f1260ff15a71 ("skbuff: introduce skb_expand_head()")
Fixes: 2d85a1b31dde ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Vasily Averin 2021-10-22 13:28:37 +03:00 • committed by Greg Kroah-Hartman
parent 3d770d44dd
commit 43e7958cf7
1 changed files with 23 additions and 13 deletions
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36
net/core/skbuff.c
View file

@ -77,6 +77,7 @@
#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;
@ -1741,30 +1742,39 @@ 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);