skb_expand_head() adjust skb->truesize incorrectly
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>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 2170bea..fe93584 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -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);