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Commit 606035e7 authored by Al Viro's avatar Al Viro
Browse files

autofs4: close the races around autofs4_notify_daemon() 



Don't drop ->wq_mutex before calling autofs4_notify_daemon() only to regain it
there.  Besides being pointless, that opens a race window where autofs4_wait_release()
could've come and freed wq->name.name.  And do the debugging printk in the "reused an
existing wq" case before dropping ->wq_mutex - the same reason...

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Acked-by: default avatarIan Kent <raven@themaw.net>
parent 3711d86a

fs/autofs4/waitq.c

+3 −10
Original line number Diff line number Diff line
@@ -109,13 +109,7 @@ static void autofs4_notify_daemon(struct autofs_sb_info *sbi, 


	pkt.hdr.proto_version = sbi->version;

	pkt.hdr.type = type;

	mutex_lock(&sbi->wq_mutex);



	/* Check if we have become catatonic */

	if (sbi->catatonic) {

		mutex_unlock(&sbi->wq_mutex);

		return;

	}

	switch (type) {

	/* Kernel protocol v4 missing and expire packets */

	case autofs_ptype_missing:
@@ -427,7 +421,6 @@ int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry, 
		wq->tgid = current->tgid;

		wq->status = -EINTR; /* Status return if interrupted */

		wq->wait_ctr = 2;

		mutex_unlock(&sbi->wq_mutex);



		if (sbi->version < 5) {

			if (notify == NFY_MOUNT)
@@ -449,15 +442,15 @@ int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry, 
			(unsigned long) wq->wait_queue_token, wq->name.len,

			wq->name.name, notify);



		/* autofs4_notify_daemon() may block */

		/* autofs4_notify_daemon() may block; it will unlock ->wq_mutex */

		autofs4_notify_daemon(sbi, wq, type);

	} else {

		wq->wait_ctr++;

		mutex_unlock(&sbi->wq_mutex);

		kfree(qstr.name);

		DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",

			(unsigned long) wq->wait_queue_token, wq->name.len,

			wq->name.name, notify);

		mutex_unlock(&sbi->wq_mutex);

		kfree(qstr.name);

	}



	/*