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:e0c9c0afd2
mnt: Update detach_mounts to leave mounts connected Fixes:ce07d891a0
mnt: Honor MNT_LOCKED when detaching mounts Cc: stable@vger.kernel.org Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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@ -1361,6 +1361,36 @@ enum umount_tree_flags {
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UMOUNT_PROPAGATE = 2,
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UMOUNT_PROPAGATE = 2,
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UMOUNT_CONNECTED = 4,
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UMOUNT_CONNECTED = 4,
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};
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};
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static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how)
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{
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/* Leaving mounts connected is only valid for lazy umounts */
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if (how & UMOUNT_SYNC)
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return true;
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/* A mount without a parent has nothing to be connected to */
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if (!mnt_has_parent(mnt))
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return true;
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/* Because the reference counting rules change when mounts are
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* unmounted and connected, umounted mounts may not be
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* connected to mounted mounts.
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*/
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if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT))
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return true;
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/* Has it been requested that the mount remain connected? */
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if (how & UMOUNT_CONNECTED)
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return false;
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/* Is the mount locked such that it needs to remain connected? */
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if (IS_MNT_LOCKED(mnt))
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return false;
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/* By default disconnect the mount */
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return true;
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}
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/*
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/*
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* mount_lock must be held
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* mount_lock must be held
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* namespace_sem must be held for write
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* namespace_sem must be held for write
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@ -1398,10 +1428,7 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
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if (how & UMOUNT_SYNC)
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if (how & UMOUNT_SYNC)
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p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
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p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
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disconnect = !(((how & UMOUNT_CONNECTED) &&
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disconnect = disconnect_mount(p, how);
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mnt_has_parent(p) &&
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(p->mnt_parent->mnt.mnt_flags & MNT_UMOUNT)) ||
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IS_MNT_LOCKED_AND_LAZY(p));
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pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt,
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pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt,
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disconnect ? &unmounted : NULL);
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disconnect ? &unmounted : NULL);
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@ -20,8 +20,6 @@
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#define SET_MNT_MARK(m) ((m)->mnt.mnt_flags |= MNT_MARKED)
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#define SET_MNT_MARK(m) ((m)->mnt.mnt_flags |= MNT_MARKED)
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#define CLEAR_MNT_MARK(m) ((m)->mnt.mnt_flags &= ~MNT_MARKED)
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#define CLEAR_MNT_MARK(m) ((m)->mnt.mnt_flags &= ~MNT_MARKED)
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#define IS_MNT_LOCKED(m) ((m)->mnt.mnt_flags & MNT_LOCKED)
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#define IS_MNT_LOCKED(m) ((m)->mnt.mnt_flags & MNT_LOCKED)
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#define IS_MNT_LOCKED_AND_LAZY(m) \
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(((m)->mnt.mnt_flags & (MNT_LOCKED|MNT_SYNC_UMOUNT)) == MNT_LOCKED)
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#define CL_EXPIRE 0x01
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#define CL_EXPIRE 0x01
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#define CL_SLAVE 0x02
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#define CL_SLAVE 0x02
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