This is a note to let you know that I've just added the patch titled
skbuff: introduce skb_expand_head()
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
skbuff-introduce-skb_expand_head.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit ffffe7a329f6a9b5e60bc7da945a9ba19d4b0376
Author: Vasily Averin <vasily.averin@xxxxxxxxx>
Date: Tue Dec 24 21:16:21 2024 -0800
skbuff: introduce skb_expand_head()
[ Upstream commit f1260ff15a71b8fc122b2c9abd8a7abffb6e0168 ]
Like skb_realloc_headroom(), new helper increases headroom of specified skb.
Unlike skb_realloc_headroom(), it does not allocate a new skb if possible;
copies skb->sk on new skb when as needed and frees original skb in case
of failures.
This helps to simplify ip[6]_finish_output2() and a few other similar cases.
Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
(cherry picked from commit f1260ff15a71b8fc122b2c9abd8a7abffb6e0168)
Signed-off-by: Harshvardhan Jha <harshvardhan.j.jha@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 3191d0ffc6e9..4edce28fb454 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1118,6 +1118,7 @@ static inline struct sk_buff *__pskb_copy(struct sk_buff *skb, int headroom,
int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, gfp_t gfp_mask);
struct sk_buff *skb_realloc_headroom(struct sk_buff *skb,
unsigned int headroom);
+struct sk_buff *skb_expand_head(struct sk_buff *skb, unsigned int headroom);
struct sk_buff *skb_copy_expand(const struct sk_buff *skb, int newheadroom,
int newtailroom, gfp_t priority);
int __must_check skb_to_sgvec_nomark(struct sk_buff *skb, struct scatterlist *sg,
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 82be36c87eb6..115c7265c7d6 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1726,6 +1726,48 @@ struct sk_buff *skb_realloc_headroom(struct sk_buff *skb, unsigned int headroom)
}
EXPORT_SYMBOL(skb_realloc_headroom);
+/**
+ * skb_expand_head - reallocate header of &sk_buff
+ * @skb: buffer to reallocate
+ * @headroom: needed headroom
+ *
+ * Unlike skb_realloc_headroom, this one does not allocate a new skb
+ * if possible; copies skb->sk to new skb as needed
+ * and frees original skb in case of failures.
+ *
+ * It expect increased headroom and generates warning otherwise.
+ */
+
+struct sk_buff *skb_expand_head(struct sk_buff *skb, unsigned int headroom)
+{
+ int delta = headroom - skb_headroom(skb);
+
+ 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)) {
+ 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);
+ }
+ skb = nskb;
+ }
+ if (skb &&
+ pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) {
+ kfree_skb(skb);
+ skb = NULL;
+ }
+ return skb;
+}
+EXPORT_SYMBOL(skb_expand_head);
+
/**
* skb_copy_expand - copy and expand sk_buff
* @skb: buffer to copy
