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Commit fcd41818 authored by Al Viro's avatar Al Viro Committed by Greg Kroah-Hartman
Browse files

propagate_one(): mnt_set_mountpoint() needs mount_lock 



commit b0d3869ce9eeacbb1bbd541909beeef4126426d5 upstream.

... to protect the modification of mp->m_count done by it.  Most of
the places that modify that thing also have namespace_lock held,
but not all of them can do so, so we really need mount_lock here.
Kudos to Piotr Krysiuk <piotras@gmail.com>, who'd spotted a related
bug in pivot_root(2) (fixed unnoticed in 5.3); search for other
similar turds has caught out this one.

Cc: stable@kernel.org
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarPiotr Krysiuk <piotras@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b1880905

fs/pnode.c

+4 −5
Original line number Diff line number Diff line
@@ -268,14 +268,13 @@ static int propagate_one(struct mount *m) 
	if (IS_ERR(child))

		return PTR_ERR(child);

	child->mnt.mnt_flags &= ~MNT_LOCKED;

	mnt_set_mountpoint(m, mp, child);

	last_dest = m;

	last_source = child;

	if (m->mnt_master != dest_master) {

	read_seqlock_excl(&mount_lock);

	mnt_set_mountpoint(m, mp, child);

	if (m->mnt_master != dest_master)

		SET_MNT_MARK(m->mnt_master);

	read_sequnlock_excl(&mount_lock);

	}

	last_dest = m;

	last_source = child;

	hlist_add_head(&child->mnt_hash, list);

	return count_mounts(m->mnt_ns, child);

}