From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Date: Wed, 1 Dec 2021 10:54:52 -0800
Subject: skbuff: introduce skb_pull_data
Patch-mainline: v5.17-rc1
Git-commit: 13244cccc2b61ec715f0ac583d3037497004d4a5
References: jsc#PED-376
Like skb_pull but returns the original data pointer before pulling the
data after performing a check against sbk->len.
This allows to change code that does "struct foo *p = (void *)skb->data;"
which is hard to audit and error prone, to:
p = skb_pull_data(skb, sizeof(*p));
if (!p)
return;
Which is both safer and cleaner.
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
include/linux/skbuff.h | 2 ++
net/core/skbuff.c | 24 ++++++++++++++++++++++++
2 files changed, 26 insertions(+)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2339,6 +2339,8 @@ static inline void *skb_pull_inline(stru
return unlikely(len > skb->len) ? NULL : __skb_pull(skb, len);
}
+void *skb_pull_data(struct sk_buff *skb, size_t len);
+
void *__pskb_pull_tail(struct sk_buff *skb, int delta);
static inline void *__pskb_pull(struct sk_buff *skb, unsigned int len)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2028,6 +2028,30 @@ void *skb_pull(struct sk_buff *skb, unsi
EXPORT_SYMBOL(skb_pull);
/**
+ * skb_pull_data - remove data from the start of a buffer returning its
+ * original position.
+ * @skb: buffer to use
+ * @len: amount of data to remove
+ *
+ * This function removes data from the start of a buffer, returning
+ * the memory to the headroom. A pointer to the original data in the buffer
+ * is returned after checking if there is enough data to pull. Once the
+ * data has been pulled future pushes will overwrite the old data.
+ */
+void *skb_pull_data(struct sk_buff *skb, size_t len)
+{
+ void *data = skb->data;
+
+ if (skb->len < len)
+ return NULL;
+
+ skb_pull(skb, len);
+
+ return data;
+}
+EXPORT_SYMBOL(skb_pull_data);
+
+/**
* skb_trim - remove end from a buffer
* @skb: buffer to alter
* @len: new length