[PATCH -next 0/3] seq_printf/puts/putc: Start to convert to return void

[PATCH -next 0/3] seq_printf/puts/putc: Start to convert to return void

[Joe Perches]

Many uses of the return value of seq_printf/seq_puts/seq_putc are
incorrect.  Many assume that the return value is the number of
chars emitted into a buffer like printf/puts/putc.

It would be better to make the return value of these functions void
to avoid these misuses.

Start to do so.
Convert seq_overflow to a public function from a static function.

Remove the return uses of seq_printf/seq_puts/seq_putc from net.
Add a seq_overflow function call instead.

Joe Perches (3):
  seq: Add a seq_overflow test.
  batman-adv: Use seq_overflow
  netfilter: Use seq_overflow

 fs/seq_file.c                                      | 15 ++++----
 include/linux/seq_file.h                           |  2 +
 include/net/netfilter/nf_conntrack_acct.h          |  3 +-
 net/batman-adv/gateway_client.c                    | 25 ++++++------
 net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c     |  6 ++-
 .../netfilter/nf_conntrack_l3proto_ipv4_compat.c   | 42 +++++++++++++--------
 net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c     |  6 ++-
 net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c     | 10 +++--
 net/netfilter/nf_conntrack_acct.c                  | 11 +++---
 net/netfilter/nf_conntrack_expect.c                |  4 +-
 net/netfilter/nf_conntrack_proto_dccp.c            | 12 ++++--
 net/netfilter/nf_conntrack_proto_gre.c             | 15 +++++---
 net/netfilter/nf_conntrack_proto_sctp.c            | 12 ++++--
 net/netfilter/nf_conntrack_proto_tcp.c             | 11 ++++--
 net/netfilter/nf_conntrack_proto_udp.c             |  7 ++--
 net/netfilter/nf_conntrack_proto_udplite.c         |  7 ++--
 net/netfilter/nf_conntrack_standalone.c            | 44 +++++++++++++---------
 net/netfilter/nf_log.c                             | 26 ++++++-------
 net/netfilter/nfnetlink_log.c                      | 12 +++---
 net/netfilter/nfnetlink_queue_core.c               | 14 ++++---
 net/netfilter/x_tables.c                           |  8 ++--
 net/netfilter/xt_hashlimit.c                       | 34 +++++++++--------
 22 files changed, 191 insertions(+), 135 deletions(-)

-- 
1.8.1.2.459.gbcd45b4.dirty

[PATCH -next 2/3] batman-adv: Use seq_overflow

[Joe Perches]

Convert the uses of the return of seq_printf to
instead check seq_overflow to determine if a buffer
overflow has occurred.

This will eventually allow seq_printf & seq_puts to
be converted to a void return instead of the often
misused return that is often assumed to be an int for
the number of bytes emitted ala printk.

Signed-off-by: Joe Perches <joe-6d6DIl74uiNBDgjK7y7TUQ@public.gmane.org>
---
 net/batman-adv/gateway_client.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
index 2449afa..dfa5d2d 100644
--- a/net/batman-adv/gateway_client.c
+++ b/net/batman-adv/gateway_client.c
@@ -517,29 +517,28 @@ static int batadv_write_buffer_text(struct batadv_priv *bat_priv,
 {
 	struct batadv_gw_node *curr_gw;
 	struct batadv_neigh_node *router;
-	int ret = -1;
 
 	router = batadv_orig_node_get_router(gw_node->orig_node);
 	if (!router)
-		goto out;
+		return -1;
 
 	curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
 
-	ret = seq_printf(seq, "%s %pM (%3i) %pM [%10s]: %u.%u/%u.%u MBit\n",
-			 (curr_gw == gw_node ? "=>" : "  "),
-			 gw_node->orig_node->orig,
-			 router->bat_iv.tq_avg, router->addr,
-			 router->if_incoming->net_dev->name,
-			 gw_node->bandwidth_down / 10,
-			 gw_node->bandwidth_down % 10,
-			 gw_node->bandwidth_up / 10,
-			 gw_node->bandwidth_up % 10);
+	seq_printf(seq, "%s %pM (%3i) %pM [%10s]: %u.%u/%u.%u MBit\n",
+		   (curr_gw == gw_node ? "=>" : "  "),
+		   gw_node->orig_node->orig,
+		   router->bat_iv.tq_avg, router->addr,
+		   router->if_incoming->net_dev->name,
+		   gw_node->bandwidth_down / 10,
+		   gw_node->bandwidth_down % 10,
+		   gw_node->bandwidth_up / 10,
+		   gw_node->bandwidth_up % 10);
 
 	batadv_neigh_node_free_ref(router);
 	if (curr_gw)
 		batadv_gw_node_free_ref(curr_gw);
-out:
-	return ret;
+
+	return seq_overflow(seq);
 }
 
 int batadv_gw_client_seq_print_text(struct seq_file *seq, void *offset)
-- 
1.8.1.2.459.gbcd45b4.dirty

Re: [PATCH -next 2/3] batman-adv: Use seq_overflow

[Antonio Quartulli]

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On 11/12/13 06:12, Joe Perches wrote:
> Convert the uses of the return of seq_printf to
> instead check seq_overflow to determine if a buffer
> overflow has occurred.
> 
> This will eventually allow seq_printf & seq_puts to
> be converted to a void return instead of the often
> misused return that is often assumed to be an int for
> the number of bytes emitted ala printk.
> 
> Signed-off-by: Joe Perches <joe-6d6DIl74uiNBDgjK7y7TUQ@public.gmane.org>

I assume this patch is going to be merged with the others in some tree.
In that case:

Acked-by: Antonio Quartulli <antonio-x4xJYDvStAgysxA8WJXlww@public.gmane.org>

Thanks,

-- 
Antonio Quartulli


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Re: [PATCH -next 2/3] batman-adv: Use seq_overflow

[Antonio Quartulli]

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Joe,

we have other places in the batman-adv code where we use seq_printf, but
at the moment we don't check the return value and we always return 0 at
the end of the function.

I think we could use seq_overflow here as well?


Thanks,


-- 
Antonio Quartulli


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Re: [PATCH -next 2/3] batman-adv: Use seq_overflow

[Al Viro]

On Wed, Dec 11, 2013 at 08:31:35AM +0100, Antonio Quartulli wrote:
> Joe,
> 
> we have other places in the batman-adv code where we use seq_printf, but
> at the moment we don't check the return value and we always return 0 at
> the end of the function.
> 
> I think we could use seq_overflow here as well?

Not if you want correctly behaving code...

Re: [PATCH -next 2/3] batman-adv: Use seq_overflow

[Al Viro]

On Tue, Dec 10, 2013 at 09:12:43PM -0800, Joe Perches wrote:

> diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
> index 2449afa..dfa5d2d 100644
> --- a/net/batman-adv/gateway_client.c
> +++ b/net/batman-adv/gateway_client.c
> @@ -517,29 +517,28 @@ static int batadv_write_buffer_text(struct batadv_priv *bat_priv,
>  {
>  	struct batadv_gw_node *curr_gw;
>  	struct batadv_neigh_node *router;
> -	int ret = -1;
>  
>  	router = batadv_orig_node_get_router(gw_node->orig_node);
>  	if (!router)
> -		goto out;
> +		return -1;

This (as well as the original) means "fail read(2) with -EINVAL", which
might or might not be correct behaviour.

>  	curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
>  
> -	ret = seq_printf(seq, "%s %pM (%3i) %pM [%10s]: %u.%u/%u.%u MBit\n",
> -			 (curr_gw == gw_node ? "=>" : "  "),
> -			 gw_node->orig_node->orig,
> -			 router->bat_iv.tq_avg, router->addr,
> -			 router->if_incoming->net_dev->name,
> -			 gw_node->bandwidth_down / 10,
> -			 gw_node->bandwidth_down % 10,
> -			 gw_node->bandwidth_up / 10,
> -			 gw_node->bandwidth_up % 10);
> +	seq_printf(seq, "%s %pM (%3i) %pM [%10s]: %u.%u/%u.%u MBit\n",
> +		   (curr_gw == gw_node ? "=>" : "  "),
> +		   gw_node->orig_node->orig,
> +		   router->bat_iv.tq_avg, router->addr,
> +		   router->if_incoming->net_dev->name,
> +		   gw_node->bandwidth_down / 10,
> +		   gw_node->bandwidth_down % 10,
> +		   gw_node->bandwidth_up / 10,
> +		   gw_node->bandwidth_up % 10);
>  
>  	batadv_neigh_node_free_ref(router);
>  	if (curr_gw)
>  		batadv_gw_node_free_ref(curr_gw);
> -out:
> -	return ret;
> +
> +	return seq_overflow(seq);

... and this is utter junk.

This sucker should return 0.  Insufficiently large buffer will be handled
by caller, TYVM, if you give that caller a chance to do so.  Returning 1
from ->show() is a bug in almost all cases, and definitely so in this one.

Just in case somebody decides that above is worth copying: It Is Not.
Original code is buggy, plain and simple.  This one trades the older
bug ("fail with -EINVAL whenever the buffer is too small") with just as buggy
"silently skip an entry entirely whenever the buffer is too small".

Don't Do That.

Re: [PATCH -next 2/3] batman-adv: Use seq_overflow

[Al Viro]

On Wed, Dec 11, 2013 at 07:55:26AM +0000, Al Viro wrote:

> This sucker should return 0.  Insufficiently large buffer will be handled
> by caller, TYVM, if you give that caller a chance to do so.  Returning 1
> from ->show() is a bug in almost all cases, and definitely so in this one.
> 
> Just in case somebody decides that above is worth copying: It Is Not.
> Original code is buggy, plain and simple.  This one trades the older
> bug ("fail with -EINVAL whenever the buffer is too small") with just as buggy
> "silently skip an entry entirely whenever the buffer is too small".
> 
> Don't Do That.

Pardon - Joe has made seq_overflow return -1 instead of true.  Correction
to the above, then - s/This trades.*\./This is just as buggy./

Conclusion is still the same - Don't Do That.  Returning -1 on insufficiently
large buffer is a bug, plain and simple.

And this patch series is completely misguided - it doesn't fix any bugs
*and* it provides a misleading example for everyone.  See the reaction
right in this thread, proposing to spread the same bug to currently
working iterators.

Re: [PATCH -next 2/3] batman-adv: Use seq_overflow

[Joe Perches]

On Wed, 2013-12-11 at 08:05 +0000, Al Viro wrote:
> On Wed, Dec 11, 2013 at 07:55:26AM +0000, Al Viro wrote:
> 
> > This sucker should return 0.  Insufficiently large buffer will be handled
> > by caller, TYVM, if you give that caller a chance to do so.  Returning 1
> > from ->show() is a bug in almost all cases, and definitely so in this one.
> > 
> > Just in case somebody decides that above is worth copying: It Is Not.
> > Original code is buggy, plain and simple.  This one trades the older
> > bug ("fail with -EINVAL whenever the buffer is too small") with just as buggy
> > "silently skip an entry entirely whenever the buffer is too small".
> > 
> > Don't Do That.
> 
> Pardon - Joe has made seq_overflow return -1 instead of true.  Correction
> to the above, then - s/This trades.*\./This is just as buggy./

Yeah, I started to use true/false, 0/1, but thought
I needed to match what seq_printf/seq_vprintf does.

> Conclusion is still the same - Don't Do That.  Returning -1 on insufficiently
> large buffer is a bug, plain and simple.

int seq_vprintf(struct seq_file *m, const char *f, va_list args)
{
	int len;

	if (m->count < m->size) {
		len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
		if (m->count + len < m->size) {
			m->count += len;
			return 0;
		}
	}
	seq_set_overflow(m);
	return -1;
}
EXPORT_SYMBOL(seq_vprintf);

int seq_printf(struct seq_file *m, const char *f, ...)
{
	int ret;
	va_list args;

	va_start(args, f);
	ret = seq_vprintf(m, f, args);
	va_end(args);

	return ret;
}
EXPORT_SYMBOL(seq_printf);

> And this patch series is completely misguided - it doesn't fix any bugs
> *and* it provides a misleading example for everyone.  See the reaction
> right in this thread, proposing to spread the same bug to currently
> working iterators.

Anyway, changing seq_overflow is easy enough

You prefer this?

bool seq_overflow(struct seq_file *seq)
{
	return m->count == m->size;
}

Re: [PATCH -next 2/3] batman-adv: Use seq_overflow

[Al Viro]

On Wed, Dec 11, 2013 at 12:26:17AM -0800, Joe Perches wrote:
> On Wed, 2013-12-11 at 08:05 +0000, Al Viro wrote:
> > On Wed, Dec 11, 2013 at 07:55:26AM +0000, Al Viro wrote:
> > 
> > > This sucker should return 0.  Insufficiently large buffer will be handled
> > > by caller, TYVM, if you give that caller a chance to do so.  Returning 1
> > > from ->show() is a bug in almost all cases, and definitely so in this one.
> > > 
> > > Just in case somebody decides that above is worth copying: It Is Not.
> > > Original code is buggy, plain and simple.  This one trades the older
> > > bug ("fail with -EINVAL whenever the buffer is too small") with just as buggy
> > > "silently skip an entry entirely whenever the buffer is too small".
> > > 
> > > Don't Do That.
> > 
> > Pardon - Joe has made seq_overflow return -1 instead of true.  Correction
> > to the above, then - s/This trades.*\./This is just as buggy./
> 
> Yeah, I started to use true/false, 0/1, but thought
> I needed to match what seq_printf/seq_vprintf does.
> 
> > Conclusion is still the same - Don't Do That.  Returning -1 on insufficiently
> > large buffer is a bug, plain and simple.
> 
> int seq_vprintf(struct seq_file *m, const char *f, va_list args)
> {
> 	int len;
> 
> 	if (m->count < m->size) {
> 		len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
> 		if (m->count + len < m->size) {
> 			m->count += len;
> 			return 0;
> 		}
> 	}
> 	seq_set_overflow(m);
> 	return -1;
> }
> EXPORT_SYMBOL(seq_vprintf);
> 
> int seq_printf(struct seq_file *m, const char *f, ...)
> {
> 	int ret;
> 	va_list args;
> 
> 	va_start(args, f);
> 	ret = seq_vprintf(m, f, args);
> 	va_end(args);
> 
> 	return ret;
> }
> EXPORT_SYMBOL(seq_printf);
> 
> > And this patch series is completely misguided - it doesn't fix any bugs
> > *and* it provides a misleading example for everyone.  See the reaction
> > right in this thread, proposing to spread the same bug to currently
> > working iterators.
> 
> Anyway, changing seq_overflow is easy enough
> 
> You prefer this?
> 
> bool seq_overflow(struct seq_file *seq)
> {
> 	return m->count == m->size;
> }

I prefer a series that starts with fixing the obvious bugs (i.e. places
where we return seq_printf/seq_puts/seq_putc return value from ->show()).
All such places should return 0.  Then we need to look at the remaining
places that check return value of seq_printf() et.al.  And decide whether
the callers really care about it.

Theoretically, there is a legitimate case when we want to look at that
return value.  Namely,
	seq_print(...)
	if (!overflowed)
		do tons of expensive calculations
		generate more output
	return 0
That is the reason why those guys hadn't been returning void to start with.
And yes, it was inviting bugs with ->show() returning -1 on overflows.
Bad API design, plain and simple.

I'm not sure we actually have any instances of that legitimate case, TBH.
_IF_ we do, we ought to expose seq_overflow() (with saner name - this one
invites the same "it's an error, need to report it" kind of bugs) and use
it in such places.  But that needs to be decided on per-caller basis.  And
I'd expect that there would be few enough such places after we kill the
obvious bugs.

[PATCH -next 3/3] netfilter: Use seq_overflow

[Joe Perches]

Convert the uses of the return of seq_printf/seq_puts/seq_putc to
use check seq_overflow to determine if a buffer overflow has occurred.

This will eventually allow seq_printf & seq_puts to be converted to a
void return instead of the often misused return that is often assumed
to be an int for the number of bytes emitted ala printk.

Convert seq_print_acct to return int.

Signed-off-by: Joe Perches <joe@perches.com>
---
 include/net/netfilter/nf_conntrack_acct.h          |  3 +-
 net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c     |  6 ++-
 .../netfilter/nf_conntrack_l3proto_ipv4_compat.c   | 42 +++++++++++++--------
 net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c     |  6 ++-
 net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c     | 10 +++--
 net/netfilter/nf_conntrack_acct.c                  | 11 +++---
 net/netfilter/nf_conntrack_expect.c                |  4 +-
 net/netfilter/nf_conntrack_proto_dccp.c            | 12 ++++--
 net/netfilter/nf_conntrack_proto_gre.c             | 15 +++++---
 net/netfilter/nf_conntrack_proto_sctp.c            | 12 ++++--
 net/netfilter/nf_conntrack_proto_tcp.c             | 11 ++++--
 net/netfilter/nf_conntrack_proto_udp.c             |  7 ++--
 net/netfilter/nf_conntrack_proto_udplite.c         |  7 ++--
 net/netfilter/nf_conntrack_standalone.c            | 44 +++++++++++++---------
 net/netfilter/nf_log.c                             | 26 ++++++-------
 net/netfilter/nfnetlink_log.c                      | 12 +++---
 net/netfilter/nfnetlink_queue_core.c               | 14 ++++---
 net/netfilter/x_tables.c                           |  8 ++--
 net/netfilter/xt_hashlimit.c                       | 34 +++++++++--------
 19 files changed, 169 insertions(+), 115 deletions(-)

diff --git a/include/net/netfilter/nf_conntrack_acct.h b/include/net/netfilter/nf_conntrack_acct.h
index 79d8d16..939bffe 100644
--- a/include/net/netfilter/nf_conntrack_acct.h
+++ b/include/net/netfilter/nf_conntrack_acct.h
@@ -46,8 +46,7 @@ struct nf_conn_acct *nf_ct_acct_ext_add(struct nf_conn *ct, gfp_t gfp)
 	return acct;
 };
 
-unsigned int seq_print_acct(struct seq_file *s, const struct nf_conn *ct,
-			    int dir);
+int seq_print_acct(struct seq_file *s, const struct nf_conn *ct, int dir);
 
 /* Check if connection tracking accounting is enabled */
 static inline bool nf_ct_acct_enabled(struct net *net)
diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
index ecd8bec..aa07f0b 100644
--- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
+++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
@@ -59,8 +59,10 @@ static bool ipv4_invert_tuple(struct nf_conntrack_tuple *tuple,
 static int ipv4_print_tuple(struct seq_file *s,
 			    const struct nf_conntrack_tuple *tuple)
 {
-	return seq_printf(s, "src=%pI4 dst=%pI4 ",
-			  &tuple->src.u3.ip, &tuple->dst.u3.ip);
+	seq_printf(s, "src=%pI4 dst=%pI4 ",
+		   &tuple->src.u3.ip, &tuple->dst.u3.ip);
+
+	return seq_overflow(s);
 }
 
 static int ipv4_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c
index 4c48e43..67ba510 100644
--- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c
+++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c
@@ -104,10 +104,10 @@ static int ct_show_secctx(struct seq_file *s, const struct nf_conn *ct)
 	if (ret)
 		return 0;
 
-	ret = seq_printf(s, "secctx=%s ", secctx);
+	seq_printf(s, "secctx=%s ", secctx);
 
 	security_release_secctx(secctx, len);
-	return ret;
+	return seq_overflow(s);
 }
 #else
 static inline int ct_show_secctx(struct seq_file *s, const struct nf_conn *ct)
@@ -141,10 +141,11 @@ static int ct_seq_show(struct seq_file *s, void *v)
 	NF_CT_ASSERT(l4proto);
 
 	ret = -ENOSPC;
-	if (seq_printf(s, "%-8s %u %ld ",
-		      l4proto->name, nf_ct_protonum(ct),
-		      timer_pending(&ct->timeout)
-		      ? (long)(ct->timeout.expires - jiffies)/HZ : 0) != 0)
+	seq_printf(s, "%-8s %u %ld ",
+		   l4proto->name, nf_ct_protonum(ct),
+		   timer_pending(&ct->timeout)
+		   ? (long)(ct->timeout.expires - jiffies)/HZ : 0);
+	if (seq_overflow(s))
 		goto release;
 
 	if (l4proto->print_conntrack && l4proto->print_conntrack(s, ct))
@@ -154,35 +155,44 @@ static int ct_seq_show(struct seq_file *s, void *v)
 			l3proto, l4proto))
 		goto release;
 
-	if (seq_print_acct(s, ct, IP_CT_DIR_ORIGINAL))
+	seq_print_acct(s, ct, IP_CT_DIR_ORIGINAL);
+	if (seq_overflow(s))
 		goto release;
 
-	if (!(test_bit(IPS_SEEN_REPLY_BIT, &ct->status)))
-		if (seq_printf(s, "[UNREPLIED] "))
+	if (!(test_bit(IPS_SEEN_REPLY_BIT, &ct->status))) {
+		seq_printf(s, "[UNREPLIED] ");
+		if (seq_overflow(s))
 			goto release;
+	}
 
 	if (print_tuple(s, &ct->tuplehash[IP_CT_DIR_REPLY].tuple,
 			l3proto, l4proto))
 		goto release;
 
-	if (seq_print_acct(s, ct, IP_CT_DIR_REPLY))
+	seq_print_acct(s, ct, IP_CT_DIR_REPLY);
+	if (seq_overflow(s))
 		goto release;
 
-	if (test_bit(IPS_ASSURED_BIT, &ct->status))
-		if (seq_printf(s, "[ASSURED] "))
+	if (test_bit(IPS_ASSURED_BIT, &ct->status)) {
+		seq_printf(s, "[ASSURED] ");
+		if (seq_overflow(s))
 			goto release;
+	}
 
 #ifdef CONFIG_NF_CONNTRACK_MARK
-	if (seq_printf(s, "mark=%u ", ct->mark))
+	seq_printf(s, "mark=%u ", ct->mark);
+	if (seq_overflow(s))
 		goto release;
 #endif
 
 	if (ct_show_secctx(s, ct))
 		goto release;
 
-	if (seq_printf(s, "use=%u\n", atomic_read(&ct->ct_general.use)))
+	seq_printf(s, "use=%u\n", atomic_read(&ct->ct_general.use));
+	if (seq_overflow(s))
 		goto release;
 	ret = 0;
+
 release:
 	nf_ct_put(ct);
 	return ret;
@@ -297,7 +307,9 @@ static int exp_seq_show(struct seq_file *s, void *v)
 		    __nf_ct_l3proto_find(exp->tuple.src.l3num),
 		    __nf_ct_l4proto_find(exp->tuple.src.l3num,
 					 exp->tuple.dst.protonum));
-	return seq_putc(s, '\n');
+	seq_putc(s, '\n');
+
+	return seq_overflow(s);
 }
 
 static const struct seq_operations exp_seq_ops = {
diff --git a/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c b/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
index 4cbc6b2..d5b0cd4 100644
--- a/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
+++ b/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
@@ -63,8 +63,10 @@ static bool ipv6_invert_tuple(struct nf_conntrack_tuple *tuple,
 static int ipv6_print_tuple(struct seq_file *s,
 			    const struct nf_conntrack_tuple *tuple)
 {
-	return seq_printf(s, "src=%pI6 dst=%pI6 ",
-			  tuple->src.u3.ip6, tuple->dst.u3.ip6);
+	seq_printf(s, "src=%pI6 dst=%pI6 ",
+		   tuple->src.u3.ip6, tuple->dst.u3.ip6);
+
+	return seq_overflow(s);
 }
 
 static int ipv6_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
diff --git a/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c b/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c
index b3807c5..4d6d138 100644
--- a/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c
+++ b/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c
@@ -87,10 +87,12 @@ static bool icmpv6_invert_tuple(struct nf_conntrack_tuple *tuple,
 static int icmpv6_print_tuple(struct seq_file *s,
 			      const struct nf_conntrack_tuple *tuple)
 {
-	return seq_printf(s, "type=%u code=%u id=%u ",
-			  tuple->dst.u.icmp.type,
-			  tuple->dst.u.icmp.code,
-			  ntohs(tuple->src.u.icmp.id));
+	seq_printf(s, "type=%u code=%u id=%u ",
+		   tuple->dst.u.icmp.type,
+		   tuple->dst.u.icmp.code,
+		   ntohs(tuple->src.u.icmp.id));
+
+	return seq_overflow(s);
 }
 
 static unsigned int *icmpv6_get_timeouts(struct net *net)
diff --git a/net/netfilter/nf_conntrack_acct.c b/net/netfilter/nf_conntrack_acct.c
index a4b5e2a..897d9cc 100644
--- a/net/netfilter/nf_conntrack_acct.c
+++ b/net/netfilter/nf_conntrack_acct.c
@@ -36,8 +36,7 @@ static struct ctl_table acct_sysctl_table[] = {
 };
 #endif /* CONFIG_SYSCTL */
 
-unsigned int
-seq_print_acct(struct seq_file *s, const struct nf_conn *ct, int dir)
+int seq_print_acct(struct seq_file *s, const struct nf_conn *ct, int dir)
 {
 	struct nf_conn_acct *acct;
 	struct nf_conn_counter *counter;
@@ -47,9 +46,11 @@ seq_print_acct(struct seq_file *s, const struct nf_conn *ct, int dir)
 		return 0;
 
 	counter = acct->counter;
-	return seq_printf(s, "packets=%llu bytes=%llu ",
-			  (unsigned long long)atomic64_read(&counter[dir].packets),
-			  (unsigned long long)atomic64_read(&counter[dir].bytes));
+	seq_printf(s, "packets=%llu bytes=%llu ",
+		   (unsigned long long)atomic64_read(&counter[dir].packets),
+		   (unsigned long long)atomic64_read(&counter[dir].bytes));
+
+	return seq_overflow(s);
 };
 EXPORT_SYMBOL_GPL(seq_print_acct);
 
diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
index 4fd1ca9..15bbf36 100644
--- a/net/netfilter/nf_conntrack_expect.c
+++ b/net/netfilter/nf_conntrack_expect.c
@@ -544,7 +544,9 @@ static int exp_seq_show(struct seq_file *s, void *v)
 				   helper->expect_policy[expect->class].name);
 	}
 
-	return seq_putc(s, '\n');
+	seq_putc(s, '\n');
+
+	return seq_overflow(s);
 }
 
 static const struct seq_operations exp_seq_ops = {
diff --git a/net/netfilter/nf_conntrack_proto_dccp.c b/net/netfilter/nf_conntrack_proto_dccp.c
index a99b6c3..a0f95a6 100644
--- a/net/netfilter/nf_conntrack_proto_dccp.c
+++ b/net/netfilter/nf_conntrack_proto_dccp.c
@@ -621,14 +621,18 @@ out_invalid:
 static int dccp_print_tuple(struct seq_file *s,
 			    const struct nf_conntrack_tuple *tuple)
 {
-	return seq_printf(s, "sport=%hu dport=%hu ",
-			  ntohs(tuple->src.u.dccp.port),
-			  ntohs(tuple->dst.u.dccp.port));
+	seq_printf(s, "sport=%hu dport=%hu ",
+		   ntohs(tuple->src.u.dccp.port),
+		   ntohs(tuple->dst.u.dccp.port));
+
+	return seq_overflow(s);
 }
 
 static int dccp_print_conntrack(struct seq_file *s, struct nf_conn *ct)
 {
-	return seq_printf(s, "%s ", dccp_state_names[ct->proto.dccp.state]);
+	seq_printf(s, "%s ", dccp_state_names[ct->proto.dccp.state]);
+
+	return seq_overflow(s);
 }
 
 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
diff --git a/net/netfilter/nf_conntrack_proto_gre.c b/net/netfilter/nf_conntrack_proto_gre.c
index 9d9c0da..234f7f6 100644
--- a/net/netfilter/nf_conntrack_proto_gre.c
+++ b/net/netfilter/nf_conntrack_proto_gre.c
@@ -230,17 +230,20 @@ static bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
 static int gre_print_tuple(struct seq_file *s,
 			   const struct nf_conntrack_tuple *tuple)
 {
-	return seq_printf(s, "srckey=0x%x dstkey=0x%x ",
-			  ntohs(tuple->src.u.gre.key),
-			  ntohs(tuple->dst.u.gre.key));
+	seq_printf(s, "srckey=0x%x dstkey=0x%x ",
+		   ntohs(tuple->src.u.gre.key), ntohs(tuple->dst.u.gre.key));
+
+	return seq_overflow(s);
 }
 
 /* print private data for conntrack */
 static int gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
 {
-	return seq_printf(s, "timeout=%u, stream_timeout=%u ",
-			  (ct->proto.gre.timeout / HZ),
-			  (ct->proto.gre.stream_timeout / HZ));
+	seq_printf(s, "timeout=%u, stream_timeout=%u ",
+		   ct->proto.gre.timeout / HZ,
+		   ct->proto.gre.stream_timeout / HZ);
+
+	return seq_overflow(s);
 }
 
 static unsigned int *gre_get_timeouts(struct net *net)
diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c
index 1314d33..b8b5708 100644
--- a/net/netfilter/nf_conntrack_proto_sctp.c
+++ b/net/netfilter/nf_conntrack_proto_sctp.c
@@ -169,9 +169,11 @@ static bool sctp_invert_tuple(struct nf_conntrack_tuple *tuple,
 static int sctp_print_tuple(struct seq_file *s,
 			    const struct nf_conntrack_tuple *tuple)
 {
-	return seq_printf(s, "sport=%hu dport=%hu ",
-			  ntohs(tuple->src.u.sctp.port),
-			  ntohs(tuple->dst.u.sctp.port));
+	seq_printf(s, "sport=%hu dport=%hu ",
+		   ntohs(tuple->src.u.sctp.port),
+		   ntohs(tuple->dst.u.sctp.port));
+
+	return seq_overflow(s);
 }
 
 /* Print out the private part of the conntrack. */
@@ -183,7 +185,9 @@ static int sctp_print_conntrack(struct seq_file *s, struct nf_conn *ct)
 	state = ct->proto.sctp.state;
 	spin_unlock_bh(&ct->lock);
 
-	return seq_printf(s, "%s ", sctp_conntrack_names[state]);
+	seq_printf(s, "%s ", sctp_conntrack_names[state]);
+
+	return seq_overflow(s);
 }
 
 #define for_each_sctp_chunk(skb, sch, _sch, offset, dataoff, count)	\
diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index 44d1ea3..d21de09e 100644
--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -305,9 +305,10 @@ static bool tcp_invert_tuple(struct nf_conntrack_tuple *tuple,
 static int tcp_print_tuple(struct seq_file *s,
 			   const struct nf_conntrack_tuple *tuple)
 {
-	return seq_printf(s, "sport=%hu dport=%hu ",
-			  ntohs(tuple->src.u.tcp.port),
-			  ntohs(tuple->dst.u.tcp.port));
+	seq_printf(s, "sport=%hu dport=%hu ",
+		   ntohs(tuple->src.u.tcp.port), ntohs(tuple->dst.u.tcp.port));
+
+	return seq_overflow(s);
 }
 
 /* Print out the private part of the conntrack. */
@@ -319,7 +320,9 @@ static int tcp_print_conntrack(struct seq_file *s, struct nf_conn *ct)
 	state = ct->proto.tcp.state;
 	spin_unlock_bh(&ct->lock);
 
-	return seq_printf(s, "%s ", tcp_conntrack_names[state]);
+	seq_printf(s, "%s ", tcp_conntrack_names[state]);
+
+	return seq_overflow(s);
 }
 
 static unsigned int get_conntrack_index(const struct tcphdr *tcph)
diff --git a/net/netfilter/nf_conntrack_proto_udp.c b/net/netfilter/nf_conntrack_proto_udp.c
index 9d7721c..c2b52da 100644
--- a/net/netfilter/nf_conntrack_proto_udp.c
+++ b/net/netfilter/nf_conntrack_proto_udp.c
@@ -66,9 +66,10 @@ static bool udp_invert_tuple(struct nf_conntrack_tuple *tuple,
 static int udp_print_tuple(struct seq_file *s,
 			   const struct nf_conntrack_tuple *tuple)
 {
-	return seq_printf(s, "sport=%hu dport=%hu ",
-			  ntohs(tuple->src.u.udp.port),
-			  ntohs(tuple->dst.u.udp.port));
+	seq_printf(s, "sport=%hu dport=%hu ",
+		   ntohs(tuple->src.u.udp.port), ntohs(tuple->dst.u.udp.port));
+
+	return seq_overflow(s);
 }
 
 static unsigned int *udp_get_timeouts(struct net *net)
diff --git a/net/netfilter/nf_conntrack_proto_udplite.c b/net/netfilter/nf_conntrack_proto_udplite.c
index 2750e6c..7c4fb9b 100644
--- a/net/netfilter/nf_conntrack_proto_udplite.c
+++ b/net/netfilter/nf_conntrack_proto_udplite.c
@@ -74,9 +74,10 @@ static bool udplite_invert_tuple(struct nf_conntrack_tuple *tuple,
 static int udplite_print_tuple(struct seq_file *s,
 			       const struct nf_conntrack_tuple *tuple)
 {
-	return seq_printf(s, "sport=%hu dport=%hu ",
-			  ntohs(tuple->src.u.udp.port),
-			  ntohs(tuple->dst.u.udp.port));
+	seq_printf(s, "sport=%hu dport=%hu ",
+		   ntohs(tuple->src.u.udp.port), ntohs(tuple->dst.u.udp.port));
+
+	return seq_overflow(s);
 }
 
 static unsigned int *udplite_get_timeouts(struct net *net)
diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index f641751..6666119 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -129,10 +129,10 @@ static int ct_show_secctx(struct seq_file *s, const struct nf_conn *ct)
 	if (ret)
 		return 0;
 
-	ret = seq_printf(s, "secctx=%s ", secctx);
+	seq_printf(s, "secctx=%s ", secctx);
 
 	security_release_secctx(secctx, len);
-	return ret;
+	return seq_overflow(s);
 }
 #else
 static inline int ct_show_secctx(struct seq_file *s, const struct nf_conn *ct)
@@ -156,8 +156,9 @@ static int ct_show_delta_time(struct seq_file *s, const struct nf_conn *ct)
 		else
 			delta_time = 0;
 
-		return seq_printf(s, "delta-time=%llu ",
-				  (unsigned long long)delta_time);
+		seq_printf(s, "delta-time=%llu ",
+			   (unsigned long long)delta_time);
+		return seq_overflow(s);
 	}
 	return 0;
 }
@@ -192,11 +193,12 @@ static int ct_seq_show(struct seq_file *s, void *v)
 	NF_CT_ASSERT(l4proto);
 
 	ret = -ENOSPC;
-	if (seq_printf(s, "%-8s %u %-8s %u %ld ",
-		       l3proto->name, nf_ct_l3num(ct),
-		       l4proto->name, nf_ct_protonum(ct),
-		       timer_pending(&ct->timeout)
-		       ? (long)(ct->timeout.expires - jiffies)/HZ : 0) != 0)
+	seq_printf(s, "%-8s %u %-8s %u %ld ",
+		   l3proto->name, nf_ct_l3num(ct),
+		   l4proto->name, nf_ct_protonum(ct),
+		   timer_pending(&ct->timeout)
+		   ? (long)(ct->timeout.expires - jiffies) / HZ : 0);
+	if (seq_overflow(s))
 		goto release;
 
 	if (l4proto->print_conntrack && l4proto->print_conntrack(s, ct))
@@ -209,9 +211,11 @@ static int ct_seq_show(struct seq_file *s, void *v)
 	if (seq_print_acct(s, ct, IP_CT_DIR_ORIGINAL))
 		goto release;
 
-	if (!(test_bit(IPS_SEEN_REPLY_BIT, &ct->status)))
-		if (seq_printf(s, "[UNREPLIED] "))
+	if (!(test_bit(IPS_SEEN_REPLY_BIT, &ct->status))) {
+		seq_printf(s, "[UNREPLIED] ");
+		if (seq_overflow(s))
 			goto release;
+	}
 
 	if (print_tuple(s, &ct->tuplehash[IP_CT_DIR_REPLY].tuple,
 			l3proto, l4proto))
@@ -220,12 +224,15 @@ static int ct_seq_show(struct seq_file *s, void *v)
 	if (seq_print_acct(s, ct, IP_CT_DIR_REPLY))
 		goto release;
 
-	if (test_bit(IPS_ASSURED_BIT, &ct->status))
-		if (seq_printf(s, "[ASSURED] "))
+	if (test_bit(IPS_ASSURED_BIT, &ct->status)) {
+		seq_printf(s, "[ASSURED] ");
+		if (seq_overflow(s))
 			goto release;
+	}
 
 #if defined(CONFIG_NF_CONNTRACK_MARK)
-	if (seq_printf(s, "mark=%u ", ct->mark))
+	seq_printf(s, "mark=%u ", ct->mark);
+	if (seq_overflow(s))
 		goto release;
 #endif
 
@@ -233,17 +240,20 @@ static int ct_seq_show(struct seq_file *s, void *v)
 		goto release;
 
 #ifdef CONFIG_NF_CONNTRACK_ZONES
-	if (seq_printf(s, "zone=%u ", nf_ct_zone(ct)))
+	seq_printf(s, "zone=%u ", nf_ct_zone(ct));
+	if (seq_overflow(s))
 		goto release;
 #endif
 
 	if (ct_show_delta_time(s, ct))
 		goto release;
 
-	if (seq_printf(s, "use=%u\n", atomic_read(&ct->ct_general.use)))
+	seq_printf(s, "use=%u\n", atomic_read(&ct->ct_general.use));
+	if (seq_overflow(s))
 		goto release;
 
-	ret = 0;
+	return 0;
+
 release:
 	nf_ct_put(ct);
 	return ret;
diff --git a/net/netfilter/nf_log.c b/net/netfilter/nf_log.c
index 85296d4..386327e 100644
--- a/net/netfilter/nf_log.c
+++ b/net/netfilter/nf_log.c
@@ -189,32 +189,32 @@ static int seq_show(struct seq_file *s, void *v)
 	loff_t *pos = v;
 	const struct nf_logger *logger;
 	struct nf_logger *t;
-	int ret;
 	struct net *net = seq_file_net(s);
 
 	logger = rcu_dereference_protected(net->nf.nf_loggers[*pos],
 					   lockdep_is_held(&nf_log_mutex));
 
 	if (!logger)
-		ret = seq_printf(s, "%2lld NONE (", *pos);
+		seq_printf(s, "%2lld NONE (", *pos);
 	else
-		ret = seq_printf(s, "%2lld %s (", *pos, logger->name);
-
-	if (ret < 0)
-		return ret;
+		seq_printf(s, "%2lld %s (", *pos, logger->name);
+	if (seq_overflow(s))
+		return seq_overflow(s);
 
 	list_for_each_entry(t, &nf_loggers_l[*pos], list[*pos]) {
-		ret = seq_printf(s, "%s", t->name);
-		if (ret < 0)
-			return ret;
+		seq_printf(s, "%s", t->name);
+		if (seq_overflow(s))
+			return seq_overflow(s);
 		if (&t->list[*pos] != nf_loggers_l[*pos].prev) {
-			ret = seq_printf(s, ",");
-			if (ret < 0)
-				return ret;
+			seq_printf(s, ",");
+			if (seq_overflow(s))
+				return seq_overflow(s);
 		}
 	}
 
-	return seq_printf(s, ")\n");
+	seq_printf(s, ")\n");
+
+	return seq_overflow(s);
 }
 
 static const struct seq_operations nflog_seq_ops = {
diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index 3c4b69e..99d4a6c 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -1001,11 +1001,13 @@ static int seq_show(struct seq_file *s, void *v)
 {
 	const struct nfulnl_instance *inst = v;
 
-	return seq_printf(s, "%5d %6d %5d %1d %5d %6d %2d\n",
-			  inst->group_num,
-			  inst->peer_portid, inst->qlen,
-			  inst->copy_mode, inst->copy_range,
-			  inst->flushtimeout, atomic_read(&inst->use));
+	seq_printf(s, "%5d %6d %5d %1d %5d %6d %2d\n",
+		   inst->group_num,
+		   inst->peer_portid, inst->qlen,
+		   inst->copy_mode, inst->copy_range,
+		   inst->flushtimeout, atomic_read(&inst->use));
+
+	return seq_overflow(s);
 }
 
 static const struct seq_operations nful_seq_ops = {
diff --git a/net/netfilter/nfnetlink_queue_core.c b/net/netfilter/nfnetlink_queue_core.c
index 21258cf..c3f4762 100644
--- a/net/netfilter/nfnetlink_queue_core.c
+++ b/net/netfilter/nfnetlink_queue_core.c
@@ -1253,12 +1253,14 @@ static int seq_show(struct seq_file *s, void *v)
 {
 	const struct nfqnl_instance *inst = v;
 
-	return seq_printf(s, "%5d %6d %5d %1d %5d %5d %5d %8d %2d\n",
-			  inst->queue_num,
-			  inst->peer_portid, inst->queue_total,
-			  inst->copy_mode, inst->copy_range,
-			  inst->queue_dropped, inst->queue_user_dropped,
-			  inst->id_sequence, 1);
+	seq_printf(s, "%5d %6d %5d %1d %5d %5d %5d %8d %2d\n",
+		   inst->queue_num,
+		   inst->peer_portid, inst->queue_total,
+		   inst->copy_mode, inst->copy_range,
+		   inst->queue_dropped, inst->queue_user_dropped,
+		   inst->id_sequence, 1);
+
+	return seq_overflow(s);
 }
 
 static const struct seq_operations nfqnl_seq_ops = {
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 227aa11..a74f49f 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -983,10 +983,12 @@ static int xt_table_seq_show(struct seq_file *seq, void *v)
 {
 	struct xt_table *table = list_entry(v, struct xt_table, list);
 
-	if (strlen(table->name))
-		return seq_printf(seq, "%s\n", table->name);
-	else
+	if (!strlen(table->name))
 		return 0;
+
+	seq_printf(seq, "%s\n", table->name);
+
+	return seq_overflow(seq);
 }
 
 static const struct seq_operations xt_table_seq_ops = {
diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
index a3910fc..c229655 100644
--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c
@@ -797,25 +797,27 @@ static int dl_seq_real_show(struct dsthash_ent *ent, u_int8_t family,
 
 	switch (family) {
 	case NFPROTO_IPV4:
-		res = seq_printf(s, "%ld %pI4:%u->%pI4:%u %u %u %u\n",
-				 (long)(ent->expires - jiffies)/HZ,
-				 &ent->dst.ip.src,
-				 ntohs(ent->dst.src_port),
-				 &ent->dst.ip.dst,
-				 ntohs(ent->dst.dst_port),
-				 ent->rateinfo.credit, ent->rateinfo.credit_cap,
-				 ent->rateinfo.cost);
+		seq_printf(s, "%ld %pI4:%u->%pI4:%u %u %u %u\n",
+			   (long)(ent->expires - jiffies)/HZ,
+			   &ent->dst.ip.src,
+			   ntohs(ent->dst.src_port),
+			   &ent->dst.ip.dst,
+			   ntohs(ent->dst.dst_port),
+			   ent->rateinfo.credit, ent->rateinfo.credit_cap,
+			   ent->rateinfo.cost);
+		res = seq_overflow(s);
 		break;
 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 	case NFPROTO_IPV6:
-		res = seq_printf(s, "%ld %pI6:%u->%pI6:%u %u %u %u\n",
-				 (long)(ent->expires - jiffies)/HZ,
-				 &ent->dst.ip6.src,
-				 ntohs(ent->dst.src_port),
-				 &ent->dst.ip6.dst,
-				 ntohs(ent->dst.dst_port),
-				 ent->rateinfo.credit, ent->rateinfo.credit_cap,
-				 ent->rateinfo.cost);
+		seq_printf(s, "%ld %pI6:%u->%pI6:%u %u %u %u\n",
+			   (long)(ent->expires - jiffies)/HZ,
+			   &ent->dst.ip6.src,
+			   ntohs(ent->dst.src_port),
+			   &ent->dst.ip6.dst,
+			   ntohs(ent->dst.dst_port),
+			   ent->rateinfo.credit, ent->rateinfo.credit_cap,
+			   ent->rateinfo.cost);
+		res = seq_overflow(s);
 		break;
 #endif
 	default:
-- 
1.8.1.2.459.gbcd45b4.dirty

Re: [PATCH -next 3/3] netfilter: Use seq_overflow

[Al Viro]

On Tue, Dec 10, 2013 at 09:12:44PM -0800, Joe Perches wrote:
> --- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
> +++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
> @@ -59,8 +59,10 @@ static bool ipv4_invert_tuple(struct nf_conntrack_tuple *tuple,
>  static int ipv4_print_tuple(struct seq_file *s,
>  			    const struct nf_conntrack_tuple *tuple)
>  {
> -	return seq_printf(s, "src=%pI4 dst=%pI4 ",
> -			  &tuple->src.u3.ip, &tuple->dst.u3.ip);
> +	seq_printf(s, "src=%pI4 dst=%pI4 ",
> +		   &tuple->src.u3.ip, &tuple->dst.u3.ip);
> +
> +	return seq_overflow(s);
>  }

I'm not at all sure we want ->print_tuple() to return anything;
if we *really* want to check overflow and skip some expensive
output, we can bloody well do that in callers of print_tuple().

> @@ -104,10 +104,10 @@ static int ct_show_secctx(struct seq_file *s, const struct nf_conn *ct)
>  	if (ret)
>  		return 0;
>  
> -	ret = seq_printf(s, "secctx=%s ", secctx);
> +	seq_printf(s, "secctx=%s ", secctx);
>  
>  	security_release_secctx(secctx, len);
> -	return ret;
> +	return seq_overflow(s);
>  }

Definitely broken.

>  static inline int ct_show_secctx(struct seq_file *s, const struct nf_conn *ct)
> @@ -141,10 +141,11 @@ static int ct_seq_show(struct seq_file *s, void *v)
>  	NF_CT_ASSERT(l4proto);
>  
>  	ret = -ENOSPC;
> -	if (seq_printf(s, "%-8s %u %ld ",
> -		      l4proto->name, nf_ct_protonum(ct),
> -		      timer_pending(&ct->timeout)
> -		      ? (long)(ct->timeout.expires - jiffies)/HZ : 0) != 0)
> +	seq_printf(s, "%-8s %u %ld ",
> +		   l4proto->name, nf_ct_protonum(ct),
> +		   timer_pending(&ct->timeout)
> +		   ? (long)(ct->timeout.expires - jiffies)/HZ : 0);
> +	if (seq_overflow(s))
>  		goto release;
>  
>  	if (l4proto->print_conntrack && l4proto->print_conntrack(s, ct))
> @@ -154,35 +155,44 @@ static int ct_seq_show(struct seq_file *s, void *v)
>  			l3proto, l4proto))
>  		goto release;
>  
> -	if (seq_print_acct(s, ct, IP_CT_DIR_ORIGINAL))
> +	seq_print_acct(s, ct, IP_CT_DIR_ORIGINAL);
> +	if (seq_overflow(s))
>  		goto release;
>  
> -	if (!(test_bit(IPS_SEEN_REPLY_BIT, &ct->status)))
> -		if (seq_printf(s, "[UNREPLIED] "))
> +	if (!(test_bit(IPS_SEEN_REPLY_BIT, &ct->status))) {
> +		seq_printf(s, "[UNREPLIED] ");
> +		if (seq_overflow(s))
>  			goto release;
> +	}
>  
>  	if (print_tuple(s, &ct->tuplehash[IP_CT_DIR_REPLY].tuple,
>  			l3proto, l4proto))
>  		goto release;
>  
> -	if (seq_print_acct(s, ct, IP_CT_DIR_REPLY))
> +	seq_print_acct(s, ct, IP_CT_DIR_REPLY);
> +	if (seq_overflow(s))
>  		goto release;
>  
> -	if (test_bit(IPS_ASSURED_BIT, &ct->status))
> -		if (seq_printf(s, "[ASSURED] "))
> +	if (test_bit(IPS_ASSURED_BIT, &ct->status)) {
> +		seq_printf(s, "[ASSURED] ");
> +		if (seq_overflow(s))
>  			goto release;
> +	}
>  
>  #ifdef CONFIG_NF_CONNTRACK_MARK
> -	if (seq_printf(s, "mark=%u ", ct->mark))
> +	seq_printf(s, "mark=%u ", ct->mark);
> +	if (seq_overflow(s))
>  		goto release;
>  #endif
>  
>  	if (ct_show_secctx(s, ct))
>  		goto release;
>  
> -	if (seq_printf(s, "use=%u\n", atomic_read(&ct->ct_general.use)))
> +	seq_printf(s, "use=%u\n", atomic_read(&ct->ct_general.use));
> +	if (seq_overflow(s))
>  		goto release;
>  	ret = 0;
> +
>  release:
>  	nf_ct_put(ct);
>  	return ret;

All this "goto release on overflow" business here is pointless, AFAICS.
In any case, returning non-zero in those cases is a bug.

> @@ -297,7 +307,9 @@ static int exp_seq_show(struct seq_file *s, void *v)
>  		    __nf_ct_l3proto_find(exp->tuple.src.l3num),
>  		    __nf_ct_l4proto_find(exp->tuple.src.l3num,
>  					 exp->tuple.dst.protonum));
> -	return seq_putc(s, '\n');
> +	seq_putc(s, '\n');
> +
> +	return seq_overflow(s);
>  }

Broken.

The rest is no better, AFAICS.  Joe, you are doing it from the wrong end;
the right approach would be something like "make ->print_tuple() return
void", etc.  As it is, you are just providing a lousy pattern to anybody
reading that.  The last thing we want is people blindly copying these
bugs just because they'd seen a "proper" way of producing that kind of
broken behaviour.  Monkey see, monkey do and all such...

Re: [PATCH -next 0/3] seq_printf/puts/putc: Start to convert to return void

[David Miller]

From: Joe Perches <joe@perches.com>
Date: Tue, 10 Dec 2013 21:12:41 -0800

> Many uses of the return value of seq_printf/seq_puts/seq_putc are
> incorrect.  Many assume that the return value is the number of
> chars emitted into a buffer like printf/puts/putc.
> 
> It would be better to make the return value of these functions void
> to avoid these misuses.
> 
> Start to do so.
> Convert seq_overflow to a public function from a static function.
> 
> Remove the return uses of seq_printf/seq_puts/seq_putc from net.
> Add a seq_overflow function call instead.

I'm fine with this going in whatever tree is appropriate for
the seq_overflow un-static change:

Acked-by: David S. Miller <davem@davemloft.net>