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authorEric W. Biederman <ebiederm@xmission.com>2015-07-17 14:15:30 -0500
committerEric W. Biederman <ebiederm@xmission.com>2015-07-22 20:33:27 -0500
commitf2d0a123bcf16d1a9cf7942ddc98e0ef77862c2b (patch)
tree9ac56ed30a08d7243a2d9bea54d85dcc488aceba /fs
parentLinux 4.2-rc1 (diff)
downloadlinux-dev-f2d0a123bcf16d1a9cf7942ddc98e0ef77862c2b.tar.xz
linux-dev-f2d0a123bcf16d1a9cf7942ddc98e0ef77862c2b.zip
mnt: Clarify and correct the disconnect logic in umount_tree
rmdir mntpoint will result in an infinite loop when there is a mount locked on the mountpoint in another mount namespace. This is because the logic to test to see if a mount should be disconnected in umount_tree is buggy. Move the logic to decide if a mount should remain connected to it's mountpoint into it's own function disconnect_mount so that clarity of expression instead of terseness of expression becomes a virtue. When the conditions where it is invalid to leave a mount connected are first ruled out, the logic for deciding if a mount should be disconnected becomes much clearer and simpler. Fixes: e0c9c0afd2fc958ffa34b697972721d81df8a56f mnt: Update detach_mounts to leave mounts connected Fixes: ce07d891a0891d3c0d0c2d73d577490486b809e1 mnt: Honor MNT_LOCKED when detaching mounts Cc: stable@vger.kernel.org Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/namespace.c35
-rw-r--r--fs/pnode.h2
2 files changed, 31 insertions, 6 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index c7cb8a526c05..7829eab0b706 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1361,6 +1361,36 @@ enum umount_tree_flags {
UMOUNT_PROPAGATE = 2,
UMOUNT_CONNECTED = 4,
};
+
+static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how)
+{
+ /* Leaving mounts connected is only valid for lazy umounts */
+ if (how & UMOUNT_SYNC)
+ return true;
+
+ /* A mount without a parent has nothing to be connected to */
+ if (!mnt_has_parent(mnt))
+ return true;
+
+ /* Because the reference counting rules change when mounts are
+ * unmounted and connected, umounted mounts may not be
+ * connected to mounted mounts.
+ */
+ if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT))
+ return true;
+
+ /* Has it been requested that the mount remain connected? */
+ if (how & UMOUNT_CONNECTED)
+ return false;
+
+ /* Is the mount locked such that it needs to remain connected? */
+ if (IS_MNT_LOCKED(mnt))
+ return false;
+
+ /* By default disconnect the mount */
+ return true;
+}
+
/*
* mount_lock must be held
* namespace_sem must be held for write
@@ -1398,10 +1428,7 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
if (how & UMOUNT_SYNC)
p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
- disconnect = !(((how & UMOUNT_CONNECTED) &&
- mnt_has_parent(p) &&
- (p->mnt_parent->mnt.mnt_flags & MNT_UMOUNT)) ||
- IS_MNT_LOCKED_AND_LAZY(p));
+ disconnect = disconnect_mount(p, how);
pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt,
disconnect ? &unmounted : NULL);
diff --git a/fs/pnode.h b/fs/pnode.h
index 7114ce6e6b9e..0fcdbe7ca648 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -20,8 +20,6 @@
#define SET_MNT_MARK(m) ((m)->mnt.mnt_flags |= MNT_MARKED)
#define CLEAR_MNT_MARK(m) ((m)->mnt.mnt_flags &= ~MNT_MARKED)
#define IS_MNT_LOCKED(m) ((m)->mnt.mnt_flags & MNT_LOCKED)
-#define IS_MNT_LOCKED_AND_LAZY(m) \
- (((m)->mnt.mnt_flags & (MNT_LOCKED|MNT_SYNC_UMOUNT)) == MNT_LOCKED)
#define CL_EXPIRE 0x01
#define CL_SLAVE 0x02