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Message-ID: <m1veifrsly.fsf@ebiederm.dsl.xmission.com>
Date: Tue, 06 Feb 2007 12:30:49 -0700
From: ebiederm@...ssion.com (Eric W. Biederman)
To: Andrew Morton <akpm@...l.org>
Cc: Linux Containers <containers@...ts.osdl.org>,
<linux-kernel@...r.kernel.org>
Subject: [PATCH] ipc: Save the ipc namespace while reading proc files.
The problem we were assuming that current->nsproxy->ipc_ns would never
change while someone has our file in /proc/sysvipc/ file open. Given
that this can change with both unshare and by passing the file
descriptor to another process that assumption is occasionally wrong.
Therefore this patch causes /proc/sysvipc/* to cache the namespace
and increment it's count when we open the file and to decrement the
count when we close the file, ensuring consistent operation with
no surprises.
Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
---
ipc/util.c | 58 +++++++++++++++++++++++++++++++++++++++++++++-------------
1 files changed, 45 insertions(+), 13 deletions(-)
diff --git a/ipc/util.c b/ipc/util.c
index a9b7a22..7fd10f1 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -739,14 +739,20 @@ int ipc_parse_version (int *cmd)
#endif /* __ARCH_WANT_IPC_PARSE_VERSION */
#ifdef CONFIG_PROC_FS
+struct ipc_proc_iter {
+ struct ipc_namespace *ns;
+ struct ipc_proc_iface *iface;
+};
+
static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
{
- struct ipc_proc_iface *iface = s->private;
+ struct ipc_proc_iter *iter = s->private;
+ struct ipc_proc_iface *iface = iter->iface;
struct kern_ipc_perm *ipc = it;
loff_t p;
struct ipc_ids *ids;
- ids = current->nsproxy->ipc_ns->ids[iface->ids];
+ ids = iter->ns->ids[iface->ids];
/* If we had an ipc id locked before, unlock it */
if (ipc && ipc != SEQ_START_TOKEN)
@@ -773,12 +779,13 @@ static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
*/
static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
{
- struct ipc_proc_iface *iface = s->private;
+ struct ipc_proc_iter *iter = s->private;
+ struct ipc_proc_iface *iface = iter->iface;
struct kern_ipc_perm *ipc;
loff_t p;
struct ipc_ids *ids;
- ids = current->nsproxy->ipc_ns->ids[iface->ids];
+ ids = iter->ns->ids[iface->ids];
/*
* Take the lock - this will be released by the corresponding
@@ -807,21 +814,23 @@ static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
static void sysvipc_proc_stop(struct seq_file *s, void *it)
{
struct kern_ipc_perm *ipc = it;
- struct ipc_proc_iface *iface = s->private;
+ struct ipc_proc_iter *iter = s->private;
+ struct ipc_proc_iface *iface = iter->iface;
struct ipc_ids *ids;
/* If we had a locked segment, release it */
if (ipc && ipc != SEQ_START_TOKEN)
ipc_unlock(ipc);
- ids = current->nsproxy->ipc_ns->ids[iface->ids];
+ ids = iter->ns->ids[iface->ids];
/* Release the lock we took in start() */
mutex_unlock(&ids->mutex);
}
static int sysvipc_proc_show(struct seq_file *s, void *it)
{
- struct ipc_proc_iface *iface = s->private;
+ struct ipc_proc_iter *iter = s->private;
+ struct ipc_proc_iface *iface = iter->iface;
if (it == SEQ_START_TOKEN)
return seq_puts(s, iface->header);
@@ -836,22 +845,45 @@ static struct seq_operations sysvipc_proc_seqops = {
.show = sysvipc_proc_show,
};
-static int sysvipc_proc_open(struct inode *inode, struct file *file) {
+static int sysvipc_proc_open(struct inode *inode, struct file *file)
+{
int ret;
struct seq_file *seq;
+ struct ipc_proc_iter *iter;
+
+ ret = -ENOMEM;
+ iter = kmalloc(sizeof(*iter), GFP_KERNEL);
+ if (!iter)
+ goto out;
ret = seq_open(file, &sysvipc_proc_seqops);
- if (!ret) {
- seq = file->private_data;
- seq->private = PDE(inode)->data;
- }
+ if (ret)
+ goto out_kfree;
+
+ seq = file->private_data;
+ seq->private = iter;
+
+ iter->iface = PDE(inode)->data;
+ iter->ns = get_ipc_ns(current->nsproxy->ipc_ns);
+out:
return ret;
+out_kfree:
+ kfree(iter);
+ goto out;
+}
+
+static int sysvipc_proc_release(struct inode *inode, struct file *file)
+{
+ struct seq_file *seq = file->private_data;
+ struct ipc_proc_iter *iter = seq->private;
+ put_ipc_ns(iter->ns);
+ return seq_release_private(inode, file);
}
static struct file_operations sysvipc_proc_fops = {
.open = sysvipc_proc_open,
.read = seq_read,
.llseek = seq_lseek,
- .release = seq_release,
+ .release = sysvipc_proc_release,
};
#endif /* CONFIG_PROC_FS */
--
1.4.4.1.g278f
-
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