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ovl: don't fail with disconnected lower NFS

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NFS mounts can be disconnected from fs root.  Don't fail the overlapping
layer check because of this.

The check is not authoritative anyway, since topology can change during or
after the check.

Reported-by: Antti Antinoja <antti@fennosys.fi> 
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 146d62e5a5 ("ovl: detect overlapping layers")
This commit is contained in:
Miklos Szeredi 2019-06-18 15:06:16 +02:00
parent 941d935ac7
commit 9179c21dc6
1 changed files with 9 additions and 17 deletions
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26
fs/overlayfs/super.c
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@ -1471,23 +1471,20 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
* Check if this layer root is a descendant of: * Check if this layer root is a descendant of:
* - another layer of this overlayfs instance * - another layer of this overlayfs instance
* - upper/work dir of any overlayfs instance * - upper/work dir of any overlayfs instance
* - a disconnected dentry (detached root)
*/ */
static int ovl_check_layer(struct super_block *sb, struct dentry *dentry, static int ovl_check_layer(struct super_block *sb, struct dentry *dentry,
const char *name) const char *name)
{ {
struct dentry *next, *parent; struct dentry *next = dentry, *parent;
bool is_root = false;
int err = 0; int err = 0;
if (!dentry || dentry == dentry->d_sb->s_root) if (!dentry)
return 0; return 0;
next = dget(dentry); parent = dget_parent(next);
/* Walk back ancestors to fs root (inclusive) looking for traps */
do { /* Walk back ancestors to root (inclusive) looking for traps */
parent = dget_parent(next); while (!err && parent != next) {
is_root = (parent == next);
if (ovl_is_inuse(parent)) { if (ovl_is_inuse(parent)) {
err = -EBUSY; err = -EBUSY;
pr_err("overlayfs: %s path overlapping in-use upperdir/workdir\n", pr_err("overlayfs: %s path overlapping in-use upperdir/workdir\n",
@ -1496,17 +1493,12 @@ static int ovl_check_layer(struct super_block *sb, struct dentry *dentry,
err = -ELOOP; err = -ELOOP;
pr_err("overlayfs: overlapping %s path\n", name); pr_err("overlayfs: overlapping %s path\n", name);
} }
dput(next);
next = parent; next = parent;
} while (!err && !is_root); parent = dget_parent(next);
dput(next);
/* Did we really walk to fs root or found a detached root? */
if (!err && next != dentry->d_sb->s_root) {
err = -ESTALE;
pr_err("overlayfs: disconnected %s path\n", name);
} }
dput(next); dput(parent);
return err; return err;
} }