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Commit 62a7375e authored by Ian Kent's avatar Ian Kent Committed by Al Viro
Browse files

vfs - check non-mountpoint dentry might block in __follow_mount_rcu() 



When following a mount in rcu-walk mode we must check if the incoming dentry
is telling us it may need to block, even if it isn't actually a mountpoint.

Signed-off-by: default avatarIan Kent <raven@themaw.net>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent b81a618d

fs/namei.c

+18 −5
Original line number Diff line number Diff line
@@ -992,6 +992,12 @@ int follow_down_one(struct path *path) 
	return 0;

}



static inline bool managed_dentry_might_block(struct dentry *dentry)

{

	return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&

		dentry->d_op->d_manage(dentry, true) < 0);

}



/*

 * Skip to top of mountpoint pile in rcuwalk mode.  We abort the rcu-walk if we

 * meet a managed dentry and we're not walking to "..".  True is returned to
@@ -1000,19 +1006,26 @@ int follow_down_one(struct path *path) 
static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,

			       struct inode **inode, bool reverse_transit)

{

	while (d_mountpoint(path->dentry)) {

	for (;;) {

		struct vfsmount *mounted;

		if (unlikely(path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) &&

		    !reverse_transit &&

		    path->dentry->d_op->d_manage(path->dentry, true) < 0)

		/*

		 * Don't forget we might have a non-mountpoint managed dentry

		 * that wants to block transit.

		 */

		*inode = path->dentry->d_inode;

		if (!reverse_transit &&

		     unlikely(managed_dentry_might_block(path->dentry)))

			return false;



		if (!d_mountpoint(path->dentry))

			break;



		mounted = __lookup_mnt(path->mnt, path->dentry, 1);

		if (!mounted)

			break;

		path->mnt = mounted;

		path->dentry = mounted->mnt_root;

		nd->seq = read_seqcount_begin(&path->dentry->d_seq);

		*inode = path->dentry->d_inode;

	}



	if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))