Commit 7c7dce92 authored by Alexander Viro's avatar Alexander Viro Committed by Linus Torvalds
Browse files

[PATCH] Fix double decrement of mqueue_mnt->mnt_count in sys_mq_open 



Fixed the refcounting on failure exits in sys_mq_open() and
cleaned the logics up.  Rules are actually pretty simple - dentry_open()
expects vfsmount and dentry to be pinned down and it either transfers
them into created struct file or drops them.  Old code had been very
confused in that area - if dentry_open() had failed either in do_open()
or do_create(), we ended up dentry and mqueue_mnt dropped twice, once
by dentry_open() cleanup and then by sys_mq_open().

Fix consists of making the rules for do_create() and do_open()
same as for dentry_open() and updating the sys_mq_open() accordingly;
that actually leads to more straightforward code and less work on
normal path.

Signed-off-by: default avatarAl Viro <aviro@redhat.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 12dbf3fc

ipc/mqueue.c

+33 −26
Original line number Original line Diff line number Diff line
@@ -599,15 +599,16 @@ static int mq_attr_ok(struct mq_attr *attr) 
static struct file *do_create(struct dentry *dir, struct dentry *dentry,

static struct file *do_create(struct dentry *dir, struct dentry *dentry,

			int oflag, mode_t mode, struct mq_attr __user *u_attr)

			int oflag, mode_t mode, struct mq_attr __user *u_attr)

{

{

	struct file *filp;

	struct mq_attr attr;

	struct mq_attr attr;

	int ret;

	int ret;





	if (u_attr != NULL) {

	if (u_attr) {

		ret = -EFAULT;

		if (copy_from_user(&attr, u_attr, sizeof(attr)))

		if (copy_from_user(&attr, u_attr, sizeof(attr)))

			return ERR_PTR(-EFAULT);

			goto out;

		ret = -EINVAL;

		if (!mq_attr_ok(&attr))

		if (!mq_attr_ok(&attr))

			return ERR_PTR(-EINVAL);

			goto out;

		/* store for use during create */

		/* store for use during create */

		dentry->d_fsdata = &attr;

		dentry->d_fsdata = &attr;

	}

	}
@@ -616,13 +617,14 @@ static struct file *do_create(struct dentry *dir, struct dentry *dentry, 
	ret = vfs_create(dir->d_inode, dentry, mode, NULL);

	ret = vfs_create(dir->d_inode, dentry, mode, NULL);

	dentry->d_fsdata = NULL;

	dentry->d_fsdata = NULL;

	if (ret)

	if (ret)

		return ERR_PTR(ret);

		goto out;





	filp = dentry_open(dentry, mqueue_mnt, oflag);

	return dentry_open(dentry, mqueue_mnt, oflag);

	if (!IS_ERR(filp))

		dget(dentry);





	return filp;

out:

	dput(dentry);

	mntput(mqueue_mnt);

	return ERR_PTR(ret);

}

}





/* Opens existing queue */

/* Opens existing queue */
@@ -630,20 +632,20 @@ static struct file *do_open(struct dentry *dentry, int oflag) 
{

{

static int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE,

static int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE,

					MAY_READ | MAY_WRITE };

					MAY_READ | MAY_WRITE };

	struct file *filp;





	if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY))

	if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY)) {

		dput(dentry);

		mntput(mqueue_mnt);

		return ERR_PTR(-EINVAL);

		return ERR_PTR(-EINVAL);

	}





	if (permission(dentry->d_inode, oflag2acc[oflag & O_ACCMODE], NULL))

	if (permission(dentry->d_inode, oflag2acc[oflag & O_ACCMODE], NULL)) {

		dput(dentry);

		mntput(mqueue_mnt);

		return ERR_PTR(-EACCES);

		return ERR_PTR(-EACCES);

	}





	filp = dentry_open(dentry, mqueue_mnt, oflag);

	return dentry_open(dentry, mqueue_mnt, oflag);



	if (!IS_ERR(filp))

		dget(dentry);



	return filp;

}

}





asmlinkage long sys_mq_open(const char __user *u_name, int oflag, mode_t mode,

asmlinkage long sys_mq_open(const char __user *u_name, int oflag, mode_t mode,
@@ -671,17 +673,20 @@ asmlinkage long sys_mq_open(const char __user *u_name, int oflag, mode_t mode, 




	if (oflag & O_CREAT) {

	if (oflag & O_CREAT) {

		if (dentry->d_inode) {	/* entry already exists */

		if (dentry->d_inode) {	/* entry already exists */

			filp = (oflag & O_EXCL) ? ERR_PTR(-EEXIST) :

			error = -EEXIST;

					do_open(dentry, oflag);

			if (oflag & O_EXCL)

				goto out;

			filp = do_open(dentry, oflag);

		} else {

		} else {

			filp = do_create(mqueue_mnt->mnt_root, dentry,

			filp = do_create(mqueue_mnt->mnt_root, dentry,

						oflag, mode, u_attr);

						oflag, mode, u_attr);

		}

		}

	} else

	} else {

		filp = (dentry->d_inode) ? do_open(dentry, oflag) :

		error = -ENOENT;

					ERR_PTR(-ENOENT);

		if (!dentry->d_inode)



			goto out;

	dput(dentry);

		filp = do_open(dentry, oflag);

	}





	if (IS_ERR(filp)) {

	if (IS_ERR(filp)) {

		error = PTR_ERR(filp);

		error = PTR_ERR(filp);
@@ -692,8 +697,10 @@ asmlinkage long sys_mq_open(const char __user *u_name, int oflag, mode_t mode, 
	fd_install(fd, filp);

	fd_install(fd, filp);

	goto out_upsem;

	goto out_upsem;





out_putfd:

out:

	dput(dentry);

	mntput(mqueue_mnt);

	mntput(mqueue_mnt);

out_putfd:

	put_unused_fd(fd);

	put_unused_fd(fd);

out_err:

out_err:

	fd = error;

	fd = error;

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