6.15-stable review patch. If anyone has any objections, please let me know.
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From: Al Viro viro@zeniv.linux.org.uk
[ Upstream commit 1f282cdc1d219c4a557f7009e81bc792820d9d9a ]
may_decode_fh() is calling has_locked_children() while holding no locks. That's an oopsable race...
The rest of the callers are safe since they are holding namespace_sem and are guaranteed a positive refcount on the mount in question.
Rename the current has_locked_children() to __has_locked_children(), make it static and switch the fs/namespace.c users to it.
Make has_locked_children() a wrapper for __has_locked_children(), calling the latter under read_seqlock_excl(&mount_lock).
Reviewed-by: Christian Brauner brauner@kernel.org Reviewed-by: Jeff Layton jlayton@kernel.org Fixes: 620c266f3949 ("fhandle: relax open_by_handle_at() permission checks") Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Sasha Levin sashal@kernel.org --- fs/namespace.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c index 1b466c54a357d..216807f772cd2 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2424,7 +2424,7 @@ void drop_collected_mounts(struct vfsmount *mnt) namespace_unlock(); }
-bool has_locked_children(struct mount *mnt, struct dentry *dentry) +static bool __has_locked_children(struct mount *mnt, struct dentry *dentry) { struct mount *child;
@@ -2438,6 +2438,16 @@ bool has_locked_children(struct mount *mnt, struct dentry *dentry) return false; }
+bool has_locked_children(struct mount *mnt, struct dentry *dentry) +{ + bool res; + + read_seqlock_excl(&mount_lock); + res = __has_locked_children(mnt, dentry); + read_sequnlock_excl(&mount_lock); + return res; +} + /* * Check that there aren't references to earlier/same mount namespaces in the * specified subtree. Such references can act as pins for mount namespaces @@ -2498,7 +2508,7 @@ struct vfsmount *clone_private_mount(const struct path *path) return ERR_PTR(-EINVAL); }
- if (has_locked_children(old_mnt, path->dentry)) + if (__has_locked_children(old_mnt, path->dentry)) return ERR_PTR(-EINVAL);
new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE); @@ -3035,7 +3045,7 @@ static struct mount *__do_loopback(struct path *old_path, int recurse) if (!may_copy_tree(old_path)) return mnt;
- if (!recurse && has_locked_children(old, old_path->dentry)) + if (!recurse && __has_locked_children(old, old_path->dentry)) return mnt;
if (recurse) @@ -3428,7 +3438,7 @@ static int do_set_group(struct path *from_path, struct path *to_path) goto out;
/* From mount should not have locked children in place of To's root */ - if (has_locked_children(from, to->mnt.mnt_root)) + if (__has_locked_children(from, to->mnt.mnt_root)) goto out;
/* Setting sharing groups is only allowed on private mounts */