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net: dsa: Remove VLA usage

PATCH In review Kees Cook 5 participants 7 messages Jul 17, 2018 – Jul 30, 2018

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Kees Cook

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#0 lore raw

PATCH v2 1/1 net: dsa: Remove VLA usage

From: Salvatore Mesoraca <[email protected]>

We avoid 2 VLAs by using a pre-allocated field in dsa_switch. We also try to avoid dynamic allocation whenever possible (when using fewer than bits-per-long ports, which is the common case).

Link http://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com open here
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Salvatore Mesoraca <[email protected]>
[kees: tweak commit subject and message slightly]
Signed-off-by Kees Cook <[email protected]>
---
 include/net/dsa.h |  3 +++
 net/dsa/dsa2.c    | 14 ++++++++++++++
 net/dsa/switch.c  | 22 ++++++++++------------
 3 files changed, 27 insertions(+), 12 deletions(-)
include/net/dsa.h +3 -0
index fdbd6082945d..461e8a7661b7 100644
@@ -259,6 +259,9 @@ struct dsa_switch {
 	/* Number of switch port queues */
 	unsigned int		num_tx_queues;
 
+	unsigned long		*bitmap;
+	unsigned long		_bitmap;
+
 	/* Dynamically allocated ports, keep last */
 	size_t num_ports;
 	struct dsa_port ports[];
net/dsa/dsa2.c +14 -0
index dc5d9af3dc80..a1917025e155 100644
@@ -775,6 +775,20 @@ struct dsa_switch *dsa_switch_alloc(struct device *dev, size_t n)
 	if (!ds)
 		return NULL;
 
+	/* We avoid allocating memory outside dsa_switch
+	 * if it is not needed.
+	 */
+	if (n <= sizeof(ds->_bitmap) * 8) {
+		ds->bitmap = &ds->_bitmap;
+	} else {
+		ds->bitmap = devm_kcalloc(dev,
+					  BITS_TO_LONGS(n),
+					  sizeof(unsigned long),
+					  GFP_KERNEL);
+		if (unlikely(!ds->bitmap))
+			return NULL;
+	}
+
 	ds->dev = dev;
 	ds->num_ports = n;
net/dsa/switch.c +10 -12
index b93511726069..142b294d3446 100644
@@ -136,21 +136,20 @@ static int dsa_switch_mdb_add(struct dsa_switch *ds,
 {
 	const struct switchdev_obj_port_mdb *mdb = info->mdb;
 	struct switchdev_trans *trans = info->trans;
-	DECLARE_BITMAP(group, ds->num_ports);
 	int port;
 
 	/* Build a mask of Multicast group members */
-	bitmap_zero(group, ds->num_ports);
+	bitmap_zero(ds->bitmap, ds->num_ports);
 	if (ds->index == info->sw_index)
-		set_bit(info->port, group);
+		set_bit(info->port, ds->bitmap);
 	for (port = 0; port < ds->num_ports; port++)
 		if (dsa_is_dsa_port(ds, port))
-			set_bit(port, group);
+			set_bit(port, ds->bitmap);
 
 	if (switchdev_trans_ph_prepare(trans))
-		return dsa_switch_mdb_prepare_bitmap(ds, mdb, group);
+		return dsa_switch_mdb_prepare_bitmap(ds, mdb, ds->bitmap);
 
-	dsa_switch_mdb_add_bitmap(ds, mdb, group);
+	dsa_switch_mdb_add_bitmap(ds, mdb, ds->bitmap);
 
 	return 0;
 }

@@ -204,21 +203,20 @@ static int dsa_switch_vlan_add(struct dsa_switch *ds,
 {
 	const struct switchdev_obj_port_vlan *vlan = info->vlan;
 	struct switchdev_trans *trans = info->trans;
-	DECLARE_BITMAP(members, ds->num_ports);
 	int port;
 
 	/* Build a mask of VLAN members */
-	bitmap_zero(members, ds->num_ports);
+	bitmap_zero(ds->bitmap, ds->num_ports);
 	if (ds->index == info->sw_index)
-		set_bit(info->port, members);
+		set_bit(info->port, ds->bitmap);
 	for (port = 0; port < ds->num_ports; port++)
 		if (dsa_is_cpu_port(ds, port) || dsa_is_dsa_port(ds, port))
-			set_bit(port, members);
+			set_bit(port, ds->bitmap);
 
 	if (switchdev_trans_ph_prepare(trans))
-		return dsa_switch_vlan_prepare_bitmap(ds, vlan, members);
+		return dsa_switch_vlan_prepare_bitmap(ds, vlan, ds->bitmap);
 
-	dsa_switch_vlan_add_bitmap(ds, vlan, members);
+	dsa_switch_vlan_add_bitmap(ds, vlan, ds->bitmap);
 
 	return 0;
 }
Signature · 6 lines
2.17.1


-- 
Kees Cook
Pixel Security
maintainer
#1 lore raw

From: Kees Cook <[email protected]>
Date: Mon, 16 Jul 2018 21:10:34 -0700

Quoted 11 lines

From: Salvatore Mesoraca <[email protected]>

We avoid 2 VLAs by using a pre-allocated field in dsa_switch. We also try to avoid dynamic allocation whenever possible (when using fewer than bits-per-long ports, which is the common case).

Link http://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com open here
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Salvatore Mesoraca <[email protected]>
[kees: tweak commit subject and message slightly]
Signed-off-by Kees Cook <[email protected]>

Florian and Andrew, please review.

maintainer Reviewed-by
#2 lore raw
Quoted 9 lines · David Miller

From: Kees Cook <[email protected]>
Date: Mon, 16 Jul 2018 21:10:34 -0700

Quoted 6 lines

From: Salvatore Mesoraca <[email protected]>

We avoid 2 VLAs by using a pre-allocated field in dsa_switch. We also try to avoid dynamic allocation whenever possible (when using fewer than bits-per-long ports, which is the common case).

Quoted 7 lines
Quoted 5 lines
Link http://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com open here
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Salvatore Mesoraca <[email protected]>
[kees: tweak commit subject and message slightly]
Signed-off-by Kees Cook <[email protected]>

Florian and Andrew, please review.

Last time there was some discussion of just always allocating it to make the code simpler. But the extra complexity is O.K.

Reviewed-by Andrew Lunn <[email protected]>

Andrew

maintainer
#3 lore raw

From: Andrew Lunn <[email protected]>
Date: Wed, 18 Jul 2018 22:37:25 +0200

Quoted 16 lines · David Miller
Quoted 15 lines

From: Kees Cook <[email protected]>
Date: Mon, 16 Jul 2018 21:10:34 -0700

Quoted 11 lines

From: Salvatore Mesoraca <[email protected]>

We avoid 2 VLAs by using a pre-allocated field in dsa_switch. We also try to avoid dynamic allocation whenever possible (when using fewer than bits-per-long ports, which is the common case).

Link http://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com open here
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Salvatore Mesoraca <[email protected]>
[kees: tweak commit subject and message slightly]
Signed-off-by Kees Cook <[email protected]>
Quoted 6 lines
Quoted 1 line

Florian and Andrew, please review.

Last time there was some discussion of just always allocating it to make the code simpler. But the extra complexity is O.K.

Reviewed-by Andrew Lunn <[email protected]>

Great, applied, thanks!

#4 lore raw
In reply to Kees Cook

Hi!

Quoted 20 lines

We avoid 2 VLAs by using a pre-allocated field in dsa_switch. We also try to avoid dynamic allocation whenever possible (when using fewer than bits-per-long ports, which is the common case).

Link http://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com open here
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Salvatore Mesoraca <[email protected]>
[kees: tweak commit subject and message slightly]
Signed-off-by Kees Cook <[email protected]>
---
 include/net/dsa.h |  3 +++
 net/dsa/dsa2.c    | 14 ++++++++++++++
 net/dsa/switch.c  | 22 ++++++++++------------
 3 files changed, 27 insertions(+), 12 deletions(-)
include/net/dsa.h +0 -0
index fdbd6082945d..461e8a7661b7 100644

include/net/dsa.h struct dsa_switch { · line 263

Quoted 5 lines
include/net/dsa.h +2 -0
@@ -259,6 +259,9 @@ struct dsa_switch {
 	/* Number of switch port queues */
 	unsigned int		num_tx_queues;
 
+	unsigned long		*bitmap;
+	unsigned long		_bitmap;

This looks rather confusing. _bitmap -> bitmap_data? bitmap_bits?

Thanks,
Pavel

Signature · 2 lines
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
#5 lore raw

Hi!

Quoted 23 lines
Quoted 23 lines

We avoid 2 VLAs by using a pre-allocated field in dsa_switch. We also try to avoid dynamic allocation whenever possible (when using fewer than bits-per-long ports, which is the common case).

Link http://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com open here
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Salvatore Mesoraca <[email protected]>
[kees: tweak commit subject and message slightly]
Signed-off-by Kees Cook <[email protected]>
---
 include/net/dsa.h |  3 +++
 net/dsa/dsa2.c    | 14 ++++++++++++++
 net/dsa/switch.c  | 22 ++++++++++------------
 3 files changed, 27 insertions(+), 12 deletions(-)
include/net/dsa.h +0 -0
index fdbd6082945d..461e8a7661b7 100644
@@ -259,6 +259,9 @@ struct dsa_switch {
 	/* Number of switch port queues */
 	unsigned int		num_tx_queues;
Quoted 4 lines

include/net/dsa.h struct dsa_switch { · line 263

Quoted 2 lines
include/net/dsa.h +2 -0
+	unsigned long		*bitmap;
+	unsigned long		_bitmap;

This looks rather confusing. _bitmap -> bitmap_data? bitmap_bits?

Actually, AFAICT that long is not used as a long, but as array of bits. So maybe char bitmap_data[8] would be more appropriate?

(resend, now with right cc list).
Pavel

Signature · 2 lines
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
#6 lore raw

From: Pavel Machek

Quoted 1 line

Sent: 29 July 2018 12:40

...

Quoted 7 lines
Quoted 4 lines

include/net/dsa.h struct dsa_switch { · line 263

Quoted 2 lines
include/net/dsa.h +2 -0
+	unsigned long		*bitmap;
+	unsigned long		_bitmap;

This looks rather confusing. _bitmap -> bitmap_data? bitmap_bits?

Actually, AFAICT that long is not used as a long, but as array of bits. So maybe char bitmap_data[8] would be more appropriate?

Unfortunately the 'bitmap' functions are defined to work in a specific way on unsigned long[].
This means, for example, that they can't use the x86 'bit' instructions.

David

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