[PATCH] net: Remove state argument from skb_find_text()

[PATCH] net: Remove state argument from skb_find_text()

[Bojan Prtvar]

No need to pass textsearch state as argument to skb_find_text().
Instead, it can be local variable.

Signed-off-by: Bojan Prtvar <prtvar.b@gmail.com>
---
This patch changes internal kernel API. I am sending it here first in hope to get some friendly review.

 include/linux/skbuff.h              |    3 +--
 net/core/skbuff.c                   |    9 ++++-----
 net/netfilter/nf_conntrack_amanda.c |   10 +++-------
 net/netfilter/xt_string.c           |    4 +---
 net/sched/em_text.c                 |    3 +--
 5 files changed, 10 insertions(+), 19 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 08074a8..6cc1b7d 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -776,8 +776,7 @@ unsigned int skb_seq_read(unsigned int consumed, const u8 **data,
 void skb_abort_seq_read(struct skb_seq_state *st);
 
 unsigned int skb_find_text(struct sk_buff *skb, unsigned int from,
-			   unsigned int to, struct ts_config *config,
-			   struct ts_state *state);
+			   unsigned int to, struct ts_config *config);
 
 /*
  * Packet hash types specify the type of hash in skb_set_hash.
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 1b62343..c0e64f7 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2747,7 +2747,6 @@ static void skb_ts_finish(struct ts_config *conf, struct ts_state *state)
  * @from: search offset
  * @to: search limit
  * @config: textsearch configuration
- * @state: uninitialized textsearch state variable
  *
  * Finds a pattern in the skb data according to the specified
  * textsearch configuration. Use textsearch_next() to retrieve
@@ -2755,17 +2754,17 @@ static void skb_ts_finish(struct ts_config *conf, struct ts_state *state)
  * to the first occurrence or UINT_MAX if no match was found.
  */
 unsigned int skb_find_text(struct sk_buff *skb, unsigned int from,
-			   unsigned int to, struct ts_config *config,
-			   struct ts_state *state)
+			   unsigned int to, struct ts_config *config)
 {
+	struct ts_state state;
 	unsigned int ret;
 
 	config->get_next_block = skb_ts_get_next_block;
 	config->finish = skb_ts_finish;
 
-	skb_prepare_seq_read(skb, from, to, TS_SKB_CB(state));
+	skb_prepare_seq_read(skb, from, to, TS_SKB_CB(&state));
 
-	ret = textsearch_find(config, state);
+	ret = textsearch_find(config, &state);
 	return (ret <= to - from ? ret : UINT_MAX);
 }
 EXPORT_SYMBOL(skb_find_text);
diff --git a/net/netfilter/nf_conntrack_amanda.c b/net/netfilter/nf_conntrack_amanda.c
index b8b95f4..57a26cc 100644
--- a/net/netfilter/nf_conntrack_amanda.c
+++ b/net/netfilter/nf_conntrack_amanda.c
@@ -88,7 +88,6 @@ static int amanda_help(struct sk_buff *skb,
 		       struct nf_conn *ct,
 		       enum ip_conntrack_info ctinfo)
 {
-	struct ts_state ts;
 	struct nf_conntrack_expect *exp;
 	struct nf_conntrack_tuple *tuple;
 	unsigned int dataoff, start, stop, off, i;
@@ -113,23 +112,20 @@ static int amanda_help(struct sk_buff *skb,
 		return NF_ACCEPT;
 	}
 
-	memset(&ts, 0, sizeof(ts));
 	start = skb_find_text(skb, dataoff, skb->len,
-			      search[SEARCH_CONNECT].ts, &ts);
+			      search[SEARCH_CONNECT].ts);
 	if (start = UINT_MAX)
 		goto out;
 	start += dataoff + search[SEARCH_CONNECT].len;
 
-	memset(&ts, 0, sizeof(ts));
 	stop = skb_find_text(skb, start, skb->len,
-			     search[SEARCH_NEWLINE].ts, &ts);
+			     search[SEARCH_NEWLINE].ts);
 	if (stop = UINT_MAX)
 		goto out;
 	stop += start;
 
 	for (i = SEARCH_DATA; i <= SEARCH_INDEX; i++) {
-		memset(&ts, 0, sizeof(ts));
-		off = skb_find_text(skb, start, stop, search[i].ts, &ts);
+		off = skb_find_text(skb, start, stop, search[i].ts);
 		if (off = UINT_MAX)
 			continue;
 		off += start + search[i].len;
diff --git a/net/netfilter/xt_string.c b/net/netfilter/xt_string.c
index d3c48b1..0bc3460 100644
--- a/net/netfilter/xt_string.c
+++ b/net/netfilter/xt_string.c
@@ -26,14 +26,12 @@ static bool
 string_mt(const struct sk_buff *skb, struct xt_action_param *par)
 {
 	const struct xt_string_info *conf = par->matchinfo;
-	struct ts_state state;
 	bool invert;
 
-	memset(&state, 0, sizeof(struct ts_state));
 	invert = conf->u.v1.flags & XT_STRING_FLAG_INVERT;
 
 	return (skb_find_text((struct sk_buff *)skb, conf->from_offset,
-			     conf->to_offset, conf->config, &state)
+			     conf->to_offset, conf->config)
 			     != UINT_MAX) ^ invert;
 }
 
diff --git a/net/sched/em_text.c b/net/sched/em_text.c
index 15d353d..21bc53f 100644
--- a/net/sched/em_text.c
+++ b/net/sched/em_text.c
@@ -34,7 +34,6 @@ static int em_text_match(struct sk_buff *skb, struct tcf_ematch *m,
 {
 	struct text_match *tm = EM_TEXT_PRIV(m);
 	int from, to;
-	struct ts_state state;
 
 	from = tcf_get_base_ptr(skb, tm->from_layer) - skb->data;
 	from += tm->from_offset;
@@ -42,7 +41,7 @@ static int em_text_match(struct sk_buff *skb, struct tcf_ematch *m,
 	to = tcf_get_base_ptr(skb, tm->to_layer) - skb->data;
 	to += tm->to_offset;
 
-	return skb_find_text(skb, from, to, tm->config, &state) != UINT_MAX;
+	return skb_find_text(skb, from, to, tm->config) != UINT_MAX;
 }
 
 static int em_text_change(struct tcf_proto *tp, void *data, int len,
-- 
1.7.9.5

Re: [PATCH] net: Remove state argument from skb_find_text()

[Dan Carpenter]

On Tue, Feb 17, 2015 at 03:49:52PM +0100, Bojan Prtvar wrote:
> No need to pass textsearch state as argument to skb_find_text().
> Instead, it can be local variable.
> 
> Signed-off-by: Bojan Prtvar <prtvar.b@gmail.com>
> ---
> This patch changes internal kernel API. I am sending it here first in hope to get some friendly review.

Hm...  That's odd.

This was added in commit 3fc7e8a6d842f ('[NET]: skb_find_text() -
Find a text pattern in skb data') and it's pretty clear that we're
deliberately passing an uninitialized struct.  Make sure that you CC
Thomas Graf <tgraf@suug.ch> on your email.

The only thing I can think of is that originally, we didn't do it your
way because we thought this would be called recursively and didn't want
to run out of stack space.  But it never has been called recursively so
your patch seems ok.

I hope you have tested this patch.  :)

Anyway, it seems like it should work to me.  I say forward it to netdev.
The worst that can happen is that you learn something.  :)

Maybe flesh out the commit message a bit.

regards,
dan carpenter