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[71.56.157.77]) by smtp.gmail.com with ESMTPSA id j13sm21001739pfc.151.2021.11.30.16.02.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Nov 2021 16:02:59 -0800 (PST) From: Luiz Augusto von Dentz To: davem@davemloft.net, kuba@kernel.org Cc: linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org, dan.carpenter@oracle.com, Luiz Augusto von Dentz Subject: [PATCH 01/15] skbuff: introduce skb_pull_data Date: Tue, 30 Nov 2021 16:02:01 -0800 Message-Id: <20211201000215.1134831-2-luiz.dentz@gmail.com> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211201000215.1134831-1-luiz.dentz@gmail.com> References: <20211201000215.1134831-1-luiz.dentz@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-bluetooth@vger.kernel.org From: Luiz Augusto von Dentz 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. Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Dan Carpenter --- include/linux/skbuff.h | 2 ++ net/core/skbuff.c | 23 +++++++++++++++++++++++ 2 files changed, 25 insertions(+) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index eba256af64a5..877dda38684a 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -2373,6 +2373,8 @@ 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) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index a33247fdb8f5..0b19833ffbce 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -2023,6 +2023,29 @@ 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; +} + /** * skb_trim - remove end from a buffer * @skb: buffer to alter