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make sure that mntns_install() doesn't end up with referral for root

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new flag: LOOKUP_DOWN.  If the starting point is overmounted, cross
into whatever's mounted on top, triggering referrals et.al.

Use that instead of follow_down_one() loop in mntns_install(), handle
errors properly.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2017-04-15 17:31:22 -04:00
parent 93893862fb
commit 4f757f3cbf
3 changed files with 50 additions and 7 deletions
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38
fs/namei.c
View file

@ -2252,6 +2252,35 @@ static inline int lookup_last(struct nameidata *nd)
return walk_component(nd, 0);
}
static int handle_lookup_down(struct nameidata *nd)
{
struct path path = nd->path;
struct inode *inode = nd->inode;
unsigned seq = nd->seq;
int err;
if (nd->flags & LOOKUP_RCU) {
/*
* don't bother with unlazy_walk on failure - we are
* at the very beginning of walk, so we lose nothing
* if we simply redo everything in non-RCU mode
*/
if (unlikely(!__follow_mount_rcu(nd, &path, &inode, &seq)))
return -ECHILD;
} else {
dget(path.dentry);
err = follow_managed(&path, nd);
if (unlikely(err < 0))
return err;
inode = d_backing_inode(path.dentry);
seq = 0;
}
path_to_nameidata(&path, nd);
nd->inode = inode;
nd->seq = seq;
return 0;
}
/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path)
{
@ -2260,6 +2289,15 @@ static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path
if (IS_ERR(s))
return PTR_ERR(s);
if (unlikely(flags & LOOKUP_DOWN)) {
err = handle_lookup_down(nd);
if (unlikely(err < 0)) {
terminate_walk(nd);
return err;
}
}
while (!(err = link_path_walk(s, nd))
&& ((err = lookup_last(nd)) > 0)) {
s = trailing_symlink(nd);