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skbuff: introduce skb_pull_data

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[ Upstream commit 13244cccc2b61ec715f0ac583d3037497004d4a5 ]

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>
Stable-dep-of: cda0d6a198e2 ("Bluetooth: qca: fix info leak when fetching fw build id")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Luiz Augusto von Dentz 2021-12-01 10:54:52 -08:00 committed by Greg Kroah-Hartman
parent 28478f4ef9
commit a9935c14a7
2 changed files with 26 additions and 0 deletions
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2
include/linux/skbuff.h
View File

@ -2447,6 +2447,8 @@ static inline void *skb_pull_inline(struct sk_buff *skb, unsigned int len)
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)

24
net/core/skbuff.c
View File

@ -2071,6 +2071,30 @@ void *skb_pull(struct sk_buff *skb, unsigned int len)
}
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