[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@xmission.com>
Cc: Serge E. Hallyn <serue@us.ibm.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Kirill Korotaev <dev@sw.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/ipc/util.c b/ipc/util.c
index 0c97cb7..115e9aa 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -738,14 +738,20 @@
#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)
@@ -772,12 +778,13 @@
*/
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
@@ -806,21 +813,23 @@
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);
@@ -835,22 +844,45 @@
.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 */