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Commit bc1fc6d8 authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Linus Torvalds
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[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: default avatarEric 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 79a81aef

ipc/util.c

+45 −13
Original line number Diff line number Diff line
@@ -738,14 +738,20 @@ 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)
@@ -772,12 +778,13 @@ 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
@@ -806,21 +813,23 @@ 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);
@@ -835,22 +844,45 @@ 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) {

	if (ret)

		goto out_kfree;



	seq = file->private_data;

		seq->private = PDE(inode)->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 */