Commit a56967e3 authored by Maxim Patlasov's avatar Maxim Patlasov Committed by Kamal Mostafa

fs/pnode.c: treat zero mnt_group_id-s as unequal

commit 7ae8fd03 upstream.

propagate_one(m) calculates "type" argument for copy_tree() like this:

>    if (m->mnt_group_id == last_dest->mnt_group_id) {
>        type = CL_MAKE_SHARED;
>    } else {
>        type = CL_SLAVE;
>        if (IS_MNT_SHARED(m))
>           type |= CL_MAKE_SHARED;
>   }

The "type" argument then governs clone_mnt() behavior with respect to flags
and mnt_master of new mount. When we iterate through a slave group, it is
possible that both current "m" and "last_dest" are not shared (although,
both are slaves, i.e. have non-NULL mnt_master-s). Then the comparison
above erroneously makes new mount shared and sets its mnt_master to
last_source->mnt_master. The patch fixes the problem by handling zero
mnt_group_id-s as though they are unequal.

The similar problem exists in the implementation of "else" clause above
when we have to ascend upward in the master/slave tree by calling:

>    last_source = last_source->mnt_master;
>    last_dest = last_source->mnt_parent;

proper number of times. The last step is governed by
"n->mnt_group_id != last_dest->mnt_group_id" condition that may lie if
both are zero. The patch fixes this case in the same way as the former one.

[AV: don't open-code an obvious helper...]
Signed-off-by: default avatarMaxim Patlasov <mpatlasov@virtuozzo.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarKamal Mostafa <kamal@canonical.com>
parent d33f4ccc
...@@ -202,6 +202,11 @@ static struct mount *last_dest, *last_source, *dest_master; ...@@ -202,6 +202,11 @@ static struct mount *last_dest, *last_source, *dest_master;
static struct mountpoint *mp; static struct mountpoint *mp;
static struct hlist_head *list; static struct hlist_head *list;
static inline bool peers(struct mount *m1, struct mount *m2)
{
return m1->mnt_group_id == m2->mnt_group_id && m1->mnt_group_id;
}
static int propagate_one(struct mount *m) static int propagate_one(struct mount *m)
{ {
struct mount *child; struct mount *child;
...@@ -212,7 +217,7 @@ static int propagate_one(struct mount *m) ...@@ -212,7 +217,7 @@ static int propagate_one(struct mount *m)
/* skip if mountpoint isn't covered by it */ /* skip if mountpoint isn't covered by it */
if (!is_subdir(mp->m_dentry, m->mnt.mnt_root)) if (!is_subdir(mp->m_dentry, m->mnt.mnt_root))
return 0; return 0;
if (m->mnt_group_id == last_dest->mnt_group_id) { if (peers(m, last_dest)) {
type = CL_MAKE_SHARED; type = CL_MAKE_SHARED;
} else { } else {
struct mount *n, *p; struct mount *n, *p;
...@@ -223,7 +228,7 @@ static int propagate_one(struct mount *m) ...@@ -223,7 +228,7 @@ static int propagate_one(struct mount *m)
last_source = last_source->mnt_master; last_source = last_source->mnt_master;
last_dest = last_source->mnt_parent; last_dest = last_source->mnt_parent;
} }
if (n->mnt_group_id != last_dest->mnt_group_id) { if (!peers(n, last_dest)) {
last_source = last_source->mnt_master; last_source = last_source->mnt_master;
last_dest = last_source->mnt_parent; last_dest = last_source->mnt_parent;
} }
......
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