Patchwork Bug#659499: bash fails to properly read /proc files

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Submitter Ben Hutchings
Date April 7, 2012, 1:01 a.m.
Message ID <1333760494.3282.29.camel@deadeye>
Download mbox | patch
Permalink /patch/151284/
State Not Applicable
Delegated to: David Miller
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Comments

Ben Hutchings - April 7, 2012, 1:01 a.m.
On Sun, 2012-02-26 at 00:11 +0000, Ben Hutchings wrote:
> On Sun, 2012-02-19 at 23:14 +0100, Cyril Brulebois wrote:
> > Hi kernel folks,
> > 
> > here's a tiny analysis I tried to perform on bash's having issues with
> > reading /proc files, which I think is related to seeking in those files.
> > I can't play much with other kernel versions right now though. My tests
> > were performed with squeeze's bpo kernel: 3.2.0-0.bpo.1-amd64 (Debian
> > 3.2.4-1~bpo60+1).
> 
> The specific problem with seeking in /proc/net/dev appears to be caused
> by this change:
> 
> commit f04565ddf52e401880f8ba51de0dff8ba51c99fd
> Author: Mihai Maruseac <mihai.maruseac@gmail.com>
> Date:   Thu Oct 20 20:45:10 2011 +0000
> 
>     dev: use name hash for dev_seq_ops
[...]

This is supposed to be fixed by:

commit 2def16ae6b0c77571200f18ba4be049b03d75579
Author: Eric Dumazet <eric.dumazet@gmail.com>
Date:   Mon Apr 2 22:33:02 2012 +0000

    net: fix /proc/net/dev regression

which will be applied some time soon.  I'm attaching the patch in case
anyone would like to test it (see
<http://kernel-handbook.alioth.debian.org/ch-common-tasks.html#s-common-official>).

Ben.

Patch

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Mon, 2 Apr 2012 22:33:02 +0000
Subject: [PATCH] net: fix /proc/net/dev regression

commit 2def16ae6b0c77571200f18ba4be049b03d75579 upstream.

Commit f04565ddf52 (dev: use name hash for dev_seq_ops) added a second
regression, as some devices are missing from /proc/net/dev if many
devices are defined.

When seq_file buffer is filled, the last ->next/show() method is
canceled (pos value is reverted to value prior ->next() call)

Problem is after above commit, we dont restart the lookup at right
position in ->start() method.

Fix this by removing the internal 'pos' pointer added in commit, since
we need to use the 'loff_t *pos' provided by seq_file layer.

This also reverts commit 5cac98dd0 (net: Fix corruption
in /proc/*/net/dev_mcast), since its not needed anymore.

Reported-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Mihai Maruseac <mmaruseac@ixiacom.com>
Tested-by:  Ben Greear <greearb@candelatech.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

 include/linux/netdevice.h |    2 --
 net/core/dev.c            |   58 ++++++++++-----------------------------------
 net/core/dev_addr_lists.c |    3 ++-
 3 files changed, 15 insertions(+), 48 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h

index 1f77540..5cbaa20 100644

--- a/include/linux/netdevice.h

+++ b/include/linux/netdevice.h

@@ -2604,8 +2604,6 @@  extern void		net_disable_timestamp(void);

 extern void *dev_seq_start(struct seq_file *seq, loff_t *pos);
 extern void *dev_seq_next(struct seq_file *seq, void *v, loff_t *pos);
 extern void dev_seq_stop(struct seq_file *seq, void *v);
-extern int dev_seq_open_ops(struct inode *inode, struct file *file,

-			    const struct seq_operations *ops);

 #endif
 
 extern int netdev_class_create_file(struct class_attribute *class_attr);
diff --git a/net/core/dev.c b/net/core/dev.c

index 6c7dc9d..c25d453 100644

--- a/net/core/dev.c

+++ b/net/core/dev.c

@@ -4028,54 +4028,41 @@  static int dev_ifconf(struct net *net, char __user *arg)

 
 #ifdef CONFIG_PROC_FS
 
-#define BUCKET_SPACE (32 - NETDEV_HASHBITS)

-

-struct dev_iter_state {

-	struct seq_net_private p;

-	unsigned int pos; /* bucket << BUCKET_SPACE + offset */

-};

+#define BUCKET_SPACE (32 - NETDEV_HASHBITS - 1)

 
 #define get_bucket(x) ((x) >> BUCKET_SPACE)
 #define get_offset(x) ((x) & ((1 << BUCKET_SPACE) - 1))
 #define set_bucket_offset(b, o) ((b) << BUCKET_SPACE | (o))
 
-static inline struct net_device *dev_from_same_bucket(struct seq_file *seq)

+static inline struct net_device *dev_from_same_bucket(struct seq_file *seq, loff_t *pos)

 {
-	struct dev_iter_state *state = seq->private;

 	struct net *net = seq_file_net(seq);
 	struct net_device *dev;
 	struct hlist_node *p;
 	struct hlist_head *h;
-	unsigned int count, bucket, offset;

+	unsigned int count = 0, offset = get_offset(*pos);

 
-	bucket = get_bucket(state->pos);

-	offset = get_offset(state->pos);

-	h = &net->dev_name_head[bucket];

-	count = 0;

+	h = &net->dev_name_head[get_bucket(*pos)];

 	hlist_for_each_entry_rcu(dev, p, h, name_hlist) {
-		if (count++ == offset) {

-			state->pos = set_bucket_offset(bucket, count);

+		if (++count == offset)

 			return dev;
-		}

 	}
 
 	return NULL;
 }
 
-static inline struct net_device *dev_from_new_bucket(struct seq_file *seq)

+static inline struct net_device *dev_from_bucket(struct seq_file *seq, loff_t *pos)

 {
-	struct dev_iter_state *state = seq->private;

 	struct net_device *dev;
 	unsigned int bucket;
 
-	bucket = get_bucket(state->pos);

 	do {
-		dev = dev_from_same_bucket(seq);

+		dev = dev_from_same_bucket(seq, pos);

 		if (dev)
 			return dev;
 
-		bucket++;

-		state->pos = set_bucket_offset(bucket, 0);

+		bucket = get_bucket(*pos) + 1;

+		*pos = set_bucket_offset(bucket, 1);

 	} while (bucket < NETDEV_HASHENTRIES);
 
 	return NULL;
@@ -4088,33 +4075,20 @@  static inline struct net_device *dev_from_new_bucket(struct seq_file *seq)

 void *dev_seq_start(struct seq_file *seq, loff_t *pos)
 	__acquires(RCU)
 {
-	struct dev_iter_state *state = seq->private;

-

 	rcu_read_lock();
 	if (!*pos)
 		return SEQ_START_TOKEN;
 
-	/* check for end of the hash */

-	if (state->pos == 0 && *pos > 1)

+	if (get_bucket(*pos) >= NETDEV_HASHENTRIES)

 		return NULL;
 
-	return dev_from_new_bucket(seq);

+	return dev_from_bucket(seq, pos);

 }
 
 void *dev_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
-	struct net_device *dev;

-

 	++*pos;
-

-	if (v == SEQ_START_TOKEN)

-		return dev_from_new_bucket(seq);

-

-	dev = dev_from_same_bucket(seq);

-	if (dev)

-		return dev;

-

-	return dev_from_new_bucket(seq);

+	return dev_from_bucket(seq, pos);

 }
 
 void dev_seq_stop(struct seq_file *seq, void *v)
@@ -4213,13 +4187,7 @@  static const struct seq_operations dev_seq_ops = {

 static int dev_seq_open(struct inode *inode, struct file *file)
 {
 	return seq_open_net(inode, file, &dev_seq_ops,
-			    sizeof(struct dev_iter_state));

-}

-

-int dev_seq_open_ops(struct inode *inode, struct file *file,

-		     const struct seq_operations *ops)

-{

-	return seq_open_net(inode, file, ops, sizeof(struct dev_iter_state));

+			    sizeof(struct seq_net_private));

 }
 
 static const struct file_operations dev_seq_fops = {
diff --git a/net/core/dev_addr_lists.c b/net/core/dev_addr_lists.c

index 29c07fe..626698f 100644

--- a/net/core/dev_addr_lists.c

+++ b/net/core/dev_addr_lists.c

@@ -696,7 +696,8 @@  static const struct seq_operations dev_mc_seq_ops = {

 
 static int dev_mc_seq_open(struct inode *inode, struct file *file)
 {
-	return dev_seq_open_ops(inode, file, &dev_mc_seq_ops);

+	return seq_open_net(inode, file, &dev_mc_seq_ops,

+			    sizeof(struct seq_net_private));

 }
 
 static const struct file_operations dev_mc_seq_fops = {
-- 

1.7.9.5