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do_move_mount(): use the parent mount returned by do_lock_mount()

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After successful do_lock_mount() call, mp.parent is set to either
real_mount(path->mnt) (for !beneath case) or to ->mnt_parent of that
(for beneath).  p is set to real_mount(path->mnt) and after
several uses it's made equal to mp.parent.  All uses prior to that
care only about p->mnt_ns and since p->mnt_ns == parent->mnt_ns,
we might as well use mp.parent all along.

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2025-08-20 13:47:43 -04:00
parent 2010464cfa
commit 842e12352c
1 changed files with 6 additions and 11 deletions
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17
fs/namespace.c
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@@ -3566,7 +3566,6 @@ static inline bool may_use_mount(struct mount *mnt)
static int do_move_mount(struct path *old_path,
struct path *new_path, enum mnt_tree_flags_t flags)
{
struct mount *p;
struct mount *old = real_mount(old_path->mnt);
int err;
bool beneath = flags & MNT_TREE_BENEATH;
@@ -3581,8 +3580,6 @@ static int do_move_mount(struct path *old_path,
if (IS_ERR(mp.parent))
return PTR_ERR(mp.parent);
p = real_mount(new_path->mnt);
if (check_mnt(old)) {
/* if the source is in our namespace... */
/* ... it should be detachable from parent */
@@ -3592,7 +3589,7 @@ static int do_move_mount(struct path *old_path,
if (IS_MNT_SHARED(old->mnt_parent))
return -EINVAL;
/* ... and the target should be in our namespace */
if (!check_mnt(p))
if (!check_mnt(mp.parent))
return -EINVAL;
} else {
/*
@@ -3605,13 +3602,13 @@ static int do_move_mount(struct path *old_path,
* subsequent checks would've rejected that, but they lose
* some corner cases if we check it early.
*/
if (old->mnt_ns == p->mnt_ns)
if (old->mnt_ns == mp.parent->mnt_ns)
return -EINVAL;
/*
* Target should be either in our namespace or in an acceptable
* anon namespace, sensu check_anonymous_mnt().
*/
if (!may_use_mount(p))
if (!may_use_mount(mp.parent))
return -EINVAL;
}
@@ -3619,22 +3616,20 @@ static int do_move_mount(struct path *old_path,
err = can_move_mount_beneath(old, new_path, mp.mp);
if (err)
return err;
p = p->mnt_parent;
}
/*
* Don't move a mount tree containing unbindable mounts to a destination
* mount which is shared.
*/
if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
if (IS_MNT_SHARED(mp.parent) && tree_contains_unbindable(old))
return -EINVAL;
if (!check_for_nsfs_mounts(old))
return -ELOOP;
if (mount_is_ancestor(old, p))
if (mount_is_ancestor(old, mp.parent))
return -ELOOP;
return attach_recursive_mnt(old, p, mp.mp);
return attach_recursive_mnt(old, mp.parent, mp.mp);
}
static int do_move_mount_old(struct path *path, const char *old_name)