rename(): avoid a deadlock in the case of parents having no common ancestor

... and fix the directory locking documentation and proof of correctness.
Holding ->s_vfs_rename_mutex *almost* prevents ->d_parent changes; the
case where we really don't want it is splicing the root of disconnected
tree to somewhere.

In other words, ->s_vfs_rename_mutex is sufficient to stabilize "X is an
ancestor of Y" only if X and Y are already in the same tree.  Otherwise
it can go from false to true, and one can construct a deadlock on that.

Make lock_two_directories() report an error in such case and update the
callers of lock_rename()/lock_rename_child() to handle such errors.

And yes, such conditions are not impossible to create ;-/

Reviewed-by: Jan Kara <[email protected]>
Signed-off-by: Al Viro <[email protected]>

diff --git a/Documentation/filesystems/directory-locking.rst b/Documentation/filesystems/directory-locking.rst
index 193c22687851a7f583cdc002ed41202e14a659f2..05ea387bc9fbcf49ba53dd4f13332207b15766ad 100644 (file)
--- a/Documentation/filesystems/directory-locking.rst
+++ b/Documentation/filesystems/directory-locking.rst
@@ -11,130 +11,268 @@ When taking the i_rwsem on multiple non-directory objects, we
 always acquire the locks in order by increasing address.  We'll call
 that "inode pointer" order in the following.
 
 always acquire the locks in order by increasing address.  We'll call
 that "inode pointer" order in the following.
 

-For our purposes all operations fall in 5 classes:

 
 

-1) read access.  Locking rules: caller locks directory we are accessing.
-The lock is taken shared.
+Primitives
+==========

 
 

-2) object creation.  Locking rules: same as above, but the lock is taken
-exclusive.
+For our purposes all operations fall in 6 classes:

 
 

-3) object removal.  Locking rules: caller locks parent, finds victim,
-locks victim and calls the method.  Locks are exclusive.
+1. read access.  Locking rules:

 
 

-4) rename() that is _not_ cross-directory.  Locking rules: caller locks
-the parent and finds source and target.  Then we decide which of the
-source and target need to be locked.  Source needs to be locked if it's a
-non-directory; target - if it's a non-directory or about to be removed.
-Take the locks that need to be taken, in inode pointer order if need
-to take both (that can happen only when both source and target are
-non-directories - the source because it wouldn't be locked otherwise
-and the target because mixing directory and non-directory is allowed
-only with RENAME_EXCHANGE, and that won't be removing the target).
-After the locks had been taken, call the method.  All locks are exclusive.
+       * lock the directory we are accessing (shared)

 
 

-5) link creation.  Locking rules:
+2. object creation.  Locking rules:

 
 

-       * lock parent
-       * check that source is not a directory
-       * lock source
-       * call the method.
+       * lock the directory we are accessing (exclusive)

 
 

-All locks are exclusive.
+3. object removal.  Locking rules:

 
 

-6) cross-directory rename.  The trickiest in the whole bunch.  Locking
-rules:
+       * lock the parent (exclusive)
+       * find the victim
+       * lock the victim (exclusive)

 
 

-       * lock the filesystem
-       * lock parents in "ancestors first" order. If one is not ancestor of
-         the other, lock the parent of source first.
-       * find source and target.
-       * if old parent is equal to or is a descendent of target
-         fail with -ENOTEMPTY
-       * if new parent is equal to or is a descendent of source
-         fail with -ELOOP
-       * Lock subdirectories involved (source before target).
-       * Lock non-directories involved, in inode pointer order.
-       * call the method.
+4. link creation.  Locking rules:
+
+       * lock the parent (exclusive)
+       * check that the source is not a directory
+       * lock the source (exclusive; probably could be weakened to shared)

 
 

-All ->i_rwsem are taken exclusive.
+5. rename that is _not_ cross-directory.  Locking rules:

 
 

-The rules above obviously guarantee that all directories that are going to be
-read, modified or removed by method will be locked by caller.
+       * lock the parent (exclusive)
+       * find the source and target
+       * decide which of the source and target need to be locked.
+         The source needs to be locked if it's a non-directory, target - if it's
+         a non-directory or about to be removed.
+       * take the locks that need to be taken (exlusive), in inode pointer order
+         if need to take both (that can happen only when both source and target
+         are non-directories - the source because it wouldn't need to be locked
+         otherwise and the target because mixing directory and non-directory is
+         allowed only with RENAME_EXCHANGE, and that won't be removing the target).

 
 

+6. cross-directory rename.  The trickiest in the whole bunch.  Locking rules:
+
+       * lock the filesystem
+       * if the parents don't have a common ancestor, fail the operation.
+       * lock the parents in "ancestors first" order (exclusive). If neither is an
+         ancestor of the other, lock the parent of source first.
+       * find the source and target.
+       * verify that the source is not a descendent of the target and
+         target is not a descendent of source; fail the operation otherwise.
+       * lock the subdirectories involved (exclusive), source before target.
+       * lock the non-directories involved (exclusive), in inode pointer order.
+
+The rules above obviously guarantee that all directories that are going
+to be read, modified or removed by method will be locked by the caller.
+
+
+Splicing
+========
+
+There is one more thing to consider - splicing.  It's not an operation
+in its own right; it may happen as part of lookup.  We speak of the
+operations on directory trees, but we obviously do not have the full
+picture of those - especially for network filesystems.  What we have
+is a bunch of subtrees visible in dcache and locking happens on those.
+Trees grow as we do operations; memory pressure prunes them.  Normally
+that's not a problem, but there is a nasty twist - what should we do
+when one growing tree reaches the root of another?  That can happen in
+several scenarios, starting from "somebody mounted two nested subtrees
+from the same NFS4 server and doing lookups in one of them has reached
+the root of another"; there's also open-by-fhandle stuff, and there's a
+possibility that directory we see in one place gets moved by the server
+to another and we run into it when we do a lookup.
+
+For a lot of reasons we want to have the same directory present in dcache
+only once.  Multiple aliases are not allowed.  So when lookup runs into
+a subdirectory that already has an alias, something needs to be done with
+dcache trees.  Lookup is already holding the parent locked.  If alias is
+a root of separate tree, it gets attached to the directory we are doing a
+lookup in, under the name we'd been looking for.  If the alias is already
+a child of the directory we are looking in, it changes name to the one
+we'd been looking for.  No extra locking is involved in these two cases.
+However, if it's a child of some other directory, the things get trickier.
+First of all, we verify that it is *not* an ancestor of our directory
+and fail the lookup if it is.  Then we try to lock the filesystem and the
+current parent of the alias.  If either trylock fails, we fail the lookup.
+If trylocks succeed, we detach the alias from its current parent and
+attach to our directory, under the name we are looking for.
+
+Note that splicing does *not* involve any modification of the filesystem;
+all we change is the view in dcache.  Moreover, holding a directory locked
+exclusive prevents such changes involving its children and holding the
+filesystem lock prevents any changes of tree topology, other than having a
+root of one tree becoming a child of directory in another.  In particular,
+if two dentries have been found to have a common ancestor after taking
+the filesystem lock, their relationship will remain unchanged until
+the lock is dropped.  So from the directory operations' point of view
+splicing is almost irrelevant - the only place where it matters is one
+step in cross-directory renames; we need to be careful when checking if
+parents have a common ancestor.
+
+
+Multiple-filesystem stuff
+=========================
+
+For some filesystems a method can involve a directory operation on
+another filesystem; it may be ecryptfs doing operation in the underlying
+filesystem, overlayfs doing something to the layers, network filesystem
+using a local one as a cache, etc.  In all such cases the operations
+on other filesystems must follow the same locking rules.  Moreover, "a
+directory operation on this filesystem might involve directory operations
+on that filesystem" should be an asymmetric relation (or, if you will,
+it should be possible to rank the filesystems so that directory operation
+on a filesystem could trigger directory operations only on higher-ranked
+ones - in these terms overlayfs ranks lower than its layers, network
+filesystem ranks lower than whatever it caches on, etc.)
+
+
+Deadlock avoidance
+==================

 
 If no directory is its own ancestor, the scheme above is deadlock-free.
 
 Proof:
 
 
 If no directory is its own ancestor, the scheme above is deadlock-free.
 
 Proof:
 

-[XXX: will be updated once we are done massaging the lock_rename()]
-       First of all, at any moment we have a linear ordering of the
-       objects - A < B iff (A is an ancestor of B) or (B is not an ancestor
-        of A and ptr(A) < ptr(B)).
-
-       That ordering can change.  However, the following is true:
-
-(1) if object removal or non-cross-directory rename holds lock on A and
-    attempts to acquire lock on B, A will remain the parent of B until we
-    acquire the lock on B.  (Proof: only cross-directory rename can change
-    the parent of object and it would have to lock the parent).
-
-(2) if cross-directory rename holds the lock on filesystem, order will not
-    change until rename acquires all locks.  (Proof: other cross-directory
-    renames will be blocked on filesystem lock and we don't start changing
-    the order until we had acquired all locks).
-
-(3) locks on non-directory objects are acquired only after locks on
-    directory objects, and are acquired in inode pointer order.
-    (Proof: all operations but renames take lock on at most one
-    non-directory object, except renames, which take locks on source and
-    target in inode pointer order in the case they are not directories.)
-
-Now consider the minimal deadlock.  Each process is blocked on
-attempt to acquire some lock and already holds at least one lock.  Let's
-consider the set of contended locks.  First of all, filesystem lock is
-not contended, since any process blocked on it is not holding any locks.
-Thus all processes are blocked on ->i_rwsem.
-
-By (3), any process holding a non-directory lock can only be
-waiting on another non-directory lock with a larger address.  Therefore
-the process holding the "largest" such lock can always make progress, and
-non-directory objects are not included in the set of contended locks.
-
-Thus link creation can't be a part of deadlock - it can't be
-blocked on source and it means that it doesn't hold any locks.
-
-Any contended object is either held by cross-directory rename or
-has a child that is also contended.  Indeed, suppose that it is held by
-operation other than cross-directory rename.  Then the lock this operation
-is blocked on belongs to child of that object due to (1).
-
-It means that one of the operations is cross-directory rename.
-Otherwise the set of contended objects would be infinite - each of them
-would have a contended child and we had assumed that no object is its
-own descendent.  Moreover, there is exactly one cross-directory rename
-(see above).
-
-Consider the object blocking the cross-directory rename.  One
-of its descendents is locked by cross-directory rename (otherwise we
-would again have an infinite set of contended objects).  But that
-means that cross-directory rename is taking locks out of order.  Due
-to (2) the order hadn't changed since we had acquired filesystem lock.
-But locking rules for cross-directory rename guarantee that we do not
-try to acquire lock on descendent before the lock on ancestor.
-Contradiction.  I.e.  deadlock is impossible.  Q.E.D.
-
+There is a ranking on the locks, such that all primitives take
+them in order of non-decreasing rank.  Namely,
+
+  * rank ->i_rwsem of non-directories on given filesystem in inode pointer
+    order.
+  * put ->i_rwsem of all directories on a filesystem at the same rank,
+    lower than ->i_rwsem of any non-directory on the same filesystem.
+  * put ->s_vfs_rename_mutex at rank lower than that of any ->i_rwsem
+    on the same filesystem.
+  * among the locks on different filesystems use the relative
+    rank of those filesystems.
+
+For example, if we have NFS filesystem caching on a local one, we have
+
+  1. ->s_vfs_rename_mutex of NFS filesystem
+  2. ->i_rwsem of directories on that NFS filesystem, same rank for all
+  3. ->i_rwsem of non-directories on that filesystem, in order of
+     increasing address of inode
+  4. ->s_vfs_rename_mutex of local filesystem
+  5. ->i_rwsem of directories on the local filesystem, same rank for all
+  6. ->i_rwsem of non-directories on local filesystem, in order of
+     increasing address of inode.
+
+It's easy to verify that operations never take a lock with rank
+lower than that of an already held lock.
+
+Suppose deadlocks are possible.  Consider the minimal deadlocked
+set of threads.  It is a cycle of several threads, each blocked on a lock
+held by the next thread in the cycle.
+
+Since the locking order is consistent with the ranking, all
+contended locks in the minimal deadlock will be of the same rank,
+i.e. they all will be ->i_rwsem of directories on the same filesystem.
+Moreover, without loss of generality we can assume that all operations
+are done directly to that filesystem and none of them has actually
+reached the method call.
+
+In other words, we have a cycle of threads, T1,..., Tn,
+and the same number of directories (D1,...,Dn) such that
+
+       T1 is blocked on D1 which is held by T2
+
+       T2 is blocked on D2 which is held by T3
+
+       ...
+
+       Tn is blocked on Dn which is held by T1.
+
+Each operation in the minimal cycle must have locked at least
+one directory and blocked on attempt to lock another.  That leaves
+only 3 possible operations: directory removal (locks parent, then
+child), same-directory rename killing a subdirectory (ditto) and
+cross-directory rename of some sort.
+
+There must be a cross-directory rename in the set; indeed,
+if all operations had been of the "lock parent, then child" sort
+we would have Dn a parent of D1, which is a parent of D2, which is
+a parent of D3, ..., which is a parent of Dn.  Relationships couldn't
+have changed since the moment directory locks had been acquired,
+so they would all hold simultaneously at the deadlock time and
+we would have a loop.
+
+Since all operations are on the same filesystem, there can't be
+more than one cross-directory rename among them.  Without loss of
+generality we can assume that T1 is the one doing a cross-directory
+rename and everything else is of the "lock parent, then child" sort.
+
+In other words, we have a cross-directory rename that locked
+Dn and blocked on attempt to lock D1, which is a parent of D2, which is
+a parent of D3, ..., which is a parent of Dn.  Relationships between
+D1,...,Dn all hold simultaneously at the deadlock time.  Moreover,
+cross-directory rename does not get to locking any directories until it
+has acquired filesystem lock and verified that directories involved have
+a common ancestor, which guarantees that ancestry relationships between
+all of them had been stable.
+
+Consider the order in which directories are locked by the
+cross-directory rename; parents first, then possibly their children.
+Dn and D1 would have to be among those, with Dn locked before D1.
+Which pair could it be?
+
+It can't be the parents - indeed, since D1 is an ancestor of Dn,
+it would be the first parent to be locked.  Therefore at least one of the
+children must be involved and thus neither of them could be a descendent
+of another - otherwise the operation would not have progressed past
+locking the parents.
+
+It can't be a parent and its child; otherwise we would've had
+a loop, since the parents are locked before the children, so the parent
+would have to be a descendent of its child.
+
+It can't be a parent and a child of another parent either.
+Otherwise the child of the parent in question would've been a descendent
+of another child.
+
+That leaves only one possibility - namely, both Dn and D1 are
+among the children, in some order.  But that is also impossible, since
+neither of the children is a descendent of another.
+
+That concludes the proof, since the set of operations with the
+properties requiered for a minimal deadlock can not exist.
+
+Note that the check for having a common ancestor in cross-directory
+rename is crucial - without it a deadlock would be possible.  Indeed,
+suppose the parents are initially in different trees; we would lock the
+parent of source, then try to lock the parent of target, only to have
+an unrelated lookup splice a distant ancestor of source to some distant
+descendent of the parent of target.   At that point we have cross-directory
+rename holding the lock on parent of source and trying to lock its
+distant ancestor.  Add a bunch of rmdir() attempts on all directories
+in between (all of those would fail with -ENOTEMPTY, had they ever gotten
+the locks) and voila - we have a deadlock.
+
+Loop avoidance
+==============

 
 These operations are guaranteed to avoid loop creation.  Indeed,
 the only operation that could introduce loops is cross-directory rename.
 
 These operations are guaranteed to avoid loop creation.  Indeed,
 the only operation that could introduce loops is cross-directory rename.

-Since the only new (parent, child) pair added by rename() is (new parent,
-source), such loop would have to contain these objects and the rest of it
-would have to exist before rename().  I.e. at the moment of loop creation
-rename() responsible for that would be holding filesystem lock and new parent
-would have to be equal to or a descendent of source.  But that means that
-new parent had been equal to or a descendent of source since the moment when
-we had acquired filesystem lock and rename() would fail with -ELOOP in that
-case.
+Suppose after the operation there is a loop; since there hadn't been such
+loops before the operation, at least on of the nodes in that loop must've
+had its parent changed.  In other words, the loop must be passing through
+the source or, in case of exchange, possibly the target.
+
+Since the operation has succeeded, neither source nor target could have
+been ancestors of each other.  Therefore the chain of ancestors starting
+in the parent of source could not have passed through the target and
+vice versa.  On the other hand, the chain of ancestors of any node could
+not have passed through the node itself, or we would've had a loop before
+the operation.  But everything other than source and target has kept
+the parent after the operation, so the operation does not change the
+chains of ancestors of (ex-)parents of source and target.  In particular,
+those chains must end after a finite number of steps.
+
+Now consider the loop created by the operation.  It passes through either
+source or target; the next node in the loop would be the ex-parent of
+target or source resp.  After that the loop would follow the chain of
+ancestors of that parent.  But as we have just shown, that chain must
+end after a finite number of steps, which means that it can't be a part
+of any loop.  Q.E.D.

 
 While this locking scheme works for arbitrary DAGs, it relies on
 ability to check that directory is a descendent of another object.  Current
 
 While this locking scheme works for arbitrary DAGs, it relies on
 ability to check that directory is a descendent of another object.  Current

diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index 9100969e7de6250de41968d763a9e6223ce5fc2e..33cd56e2ca1a50622ee8c967d5d880a979f09930 100644 (file)
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1079,3 +1079,12 @@ On same-directory ->rename() the (tautological) update of .. is not protected
 by any locks; just don't do it if the old parent is the same as the new one.
 We really can't lock two subdirectories in same-directory rename - not without
 deadlocks.
 by any locks; just don't do it if the old parent is the same as the new one.
 We really can't lock two subdirectories in same-directory rename - not without
 deadlocks.

+
+---
+
+**mandatory**
+
+lock_rename() and lock_rename_child() may fail in cross-directory case, if
+their arguments do not have a common ancestor.  In that case ERR_PTR(-EXDEV)
+is returned, with no locks taken.  In-tree users updated; out-of-tree ones
+would need to do so.

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 7bf7a5fcc045f86a98881657e6da2acc06be98dc..7ade836beb58450f8a5eb389fac1df0f722ac8ed 100644 (file)
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -305,6 +305,8 @@ try_again:
 
        /* do the multiway lock magic */
        trap = lock_rename(cache->graveyard, dir);
 
        /* do the multiway lock magic */
        trap = lock_rename(cache->graveyard, dir);

+       if (IS_ERR(trap))
+               return PTR_ERR(trap);

 
        /* do some checks before getting the grave dentry */
        if (rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) {
 
        /* do some checks before getting the grave dentry */
        if (rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) {

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index a25dd3d20008bfa40d2fc81b797f4dfa3f9118db..8efd20dc902bf39875507e22bd94de5c25c4ed83 100644 (file)
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -599,6 +599,8 @@ ecryptfs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
        target_inode = d_inode(new_dentry);
 
        trap = lock_rename(lower_old_dir_dentry, lower_new_dir_dentry);
        target_inode = d_inode(new_dentry);
 
        trap = lock_rename(lower_old_dir_dentry, lower_new_dir_dentry);

+       if (IS_ERR(trap))
+               return PTR_ERR(trap);

        dget(lower_new_dentry);
        rc = -EINVAL;
        if (lower_old_dentry->d_parent != lower_old_dir_dentry)
        dget(lower_new_dentry);
        rc = -EINVAL;
        if (lower_old_dentry->d_parent != lower_old_dir_dentry)

diff --git a/fs/namei.c b/fs/namei.c
index 29bafbdb44ca86312ec73cc21598f8bae28ec793..6b0302ac80d1408470ef147ae13cd28309c607c8 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3014,21 +3014,37 @@ static inline int may_create(struct mnt_idmap *idmap,
        return inode_permission(idmap, dir, MAY_WRITE | MAY_EXEC);
 }
 
        return inode_permission(idmap, dir, MAY_WRITE | MAY_EXEC);
 }
 

+// p1 != p2, both are on the same filesystem, ->s_vfs_rename_mutex is held

 static struct dentry *lock_two_directories(struct dentry *p1, struct dentry *p2)
 {
 static struct dentry *lock_two_directories(struct dentry *p1, struct dentry *p2)
 {

-       struct dentry *p;
+       struct dentry *p = p1, *q = p2, *r;

 
 

-       p = d_ancestor(p2, p1);
-       if (p) {
+       while ((r = p->d_parent) != p2 && r != p)
+               p = r;
+       if (r == p2) {
+               // p is a child of p2 and an ancestor of p1 or p1 itself

                inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
                inode_lock_nested(p1->d_inode, I_MUTEX_PARENT2);
                return p;
        }
                inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
                inode_lock_nested(p1->d_inode, I_MUTEX_PARENT2);
                return p;
        }

-
-       p = d_ancestor(p1, p2);
-       inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
-       inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
-       return p;
+       // p is the root of connected component that contains p1
+       // p2 does not occur on the path from p to p1
+       while ((r = q->d_parent) != p1 && r != p && r != q)
+               q = r;
+       if (r == p1) {
+               // q is a child of p1 and an ancestor of p2 or p2 itself
+               inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
+               inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
+               return q;
+       } else if (likely(r == p)) {
+               // both p2 and p1 are descendents of p
+               inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
+               inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
+               return NULL;
+       } else { // no common ancestor at the time we'd been called
+               mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
+               return ERR_PTR(-EXDEV);
+       }

 }
 
 /*
 }
 
 /*


@@ -4947,6 +4963,10 @@ retry:
 
 retry_deleg:
        trap = lock_rename(new_path.dentry, old_path.dentry);
 
 retry_deleg:
        trap = lock_rename(new_path.dentry, old_path.dentry);

+       if (IS_ERR(trap)) {
+               error = PTR_ERR(trap);
+               goto exit_lock_rename;
+       }

 
        old_dentry = lookup_one_qstr_excl(&old_last, old_path.dentry,
                                          lookup_flags);
 
        old_dentry = lookup_one_qstr_excl(&old_last, old_path.dentry,
                                          lookup_flags);


@@ -5014,6 +5034,7 @@ exit4:
        dput(old_dentry);
 exit3:
        unlock_rename(new_path.dentry, old_path.dentry);
        dput(old_dentry);
 exit3:
        unlock_rename(new_path.dentry, old_path.dentry);

+exit_lock_rename:

        if (delegated_inode) {
                error = break_deleg_wait(&delegated_inode);
                if (!error)
        if (delegated_inode) {
                error = break_deleg_wait(&delegated_inode);
                if (!error)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index fbbea7498f02b4845c2302f84f91c5b0f555b5a6..a99260c3f9bc3e3820bbb36556293f066067550e 100644 (file)
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1813,6 +1813,10 @@ retry:
        }
 
        trap = lock_rename(tdentry, fdentry);
        }
 
        trap = lock_rename(tdentry, fdentry);

+       if (IS_ERR(trap)) {
+               err = (rqstp->rq_vers == 2) ? nfserr_acces : nfserr_xdev;
+               goto out;
+       }

        err = fh_fill_pre_attrs(ffhp);
        if (err != nfs_ok)
                goto out_unlock;
        err = fh_fill_pre_attrs(ffhp);
        if (err != nfs_ok)
                goto out_unlock;

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 4382881b070948cc21425c330153db7eebd065a0..e44dc5f661610d760f69bd73e71685b81af86e22 100644 (file)
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -722,7 +722,7 @@ static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c)
        struct inode *inode;
        struct inode *udir = d_inode(c->destdir), *wdir = d_inode(c->workdir);
        struct path path = { .mnt = ovl_upper_mnt(ofs) };
        struct inode *inode;
        struct inode *udir = d_inode(c->destdir), *wdir = d_inode(c->workdir);
        struct path path = { .mnt = ovl_upper_mnt(ofs) };

-       struct dentry *temp, *upper;
+       struct dentry *temp, *upper, *trap;

        struct ovl_cu_creds cc;
        int err;
        struct ovl_cattr cattr = {
        struct ovl_cu_creds cc;
        int err;
        struct ovl_cattr cattr = {


@@ -760,9 +760,11 @@ static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c)
         * If temp was moved, abort without the cleanup.
         */
        ovl_start_write(c->dentry);
         * If temp was moved, abort without the cleanup.
         */
        ovl_start_write(c->dentry);

-       if (lock_rename(c->workdir, c->destdir) != NULL ||
-           temp->d_parent != c->workdir) {
+       trap = lock_rename(c->workdir, c->destdir);
+       if (trap || temp->d_parent != c->workdir) {

                err = -EIO;
                err = -EIO;

+               if (IS_ERR(trap))
+                       goto out;

                goto unlock;
        } else if (err) {
                goto cleanup;
                goto unlock;
        } else if (err) {
                goto cleanup;


@@ -803,6 +805,7 @@ static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c)
                ovl_set_flag(OVL_WHITEOUTS, inode);
 unlock:
        unlock_rename(c->workdir, c->destdir);
                ovl_set_flag(OVL_WHITEOUTS, inode);
 unlock:
        unlock_rename(c->workdir, c->destdir);

+out:

        ovl_end_write(c->dentry);
 
        return err;
        ovl_end_write(c->dentry);
 
        return err;

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index aab3f5d93556f90575aec60bf99fae042e92eea1..0f8b4a719237c7202bbf89d8e9fb192b2f2e1a77 100644 (file)
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -1180,6 +1180,10 @@ static int ovl_rename(struct mnt_idmap *idmap, struct inode *olddir,
        }
 
        trap = lock_rename(new_upperdir, old_upperdir);
        }
 
        trap = lock_rename(new_upperdir, old_upperdir);

+       if (IS_ERR(trap)) {
+               err = PTR_ERR(trap);
+               goto out_revert_creds;
+       }

 
        olddentry = ovl_lookup_upper(ofs, old->d_name.name, old_upperdir,
                                     old->d_name.len);
 
        olddentry = ovl_lookup_upper(ofs, old->d_name.name, old_upperdir,
                                     old->d_name.len);

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index a0967bb250036d38c6ee922950aec7f46608aed3..fc3a6ff648bdc464b8d20ed5376c1ba275e62283 100644 (file)
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -439,8 +439,10 @@ static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
        bool ok = false;
 
        if (workdir != upperdir) {
        bool ok = false;
 
        if (workdir != upperdir) {

-               ok = (lock_rename(workdir, upperdir) == NULL);
-               unlock_rename(workdir, upperdir);
+               struct dentry *trap = lock_rename(workdir, upperdir);
+               if (!IS_ERR(trap))
+                       unlock_rename(workdir, upperdir);
+               ok = (trap == NULL);

        }
        return ok;
 }
        }
        return ok;
 }

diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 50a201e9cd398aab74a61634f26e51a7f6b47893..7b667345e6731683650b9a3a57f9dc4019729401 100644 (file)
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -1198,12 +1198,17 @@ void ovl_nlink_end(struct dentry *dentry)
 
 int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir)
 {
 
 int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir)
 {

+       struct dentry *trap;
+

        /* Workdir should not be the same as upperdir */
        if (workdir == upperdir)
                goto err;
 
        /* Workdir should not be subdir of upperdir and vice versa */
        /* Workdir should not be the same as upperdir */
        if (workdir == upperdir)
                goto err;
 
        /* Workdir should not be subdir of upperdir and vice versa */

-       if (lock_rename(workdir, upperdir) != NULL)
+       trap = lock_rename(workdir, upperdir);
+       if (IS_ERR(trap))
+               goto err;
+       if (trap)

                goto err_unlock;
 
        return 0;
                goto err_unlock;
 
        return 0;

diff --git a/fs/smb/server/vfs.c b/fs/smb/server/vfs.c
index c53dea5598fc63718e5df7f42e2079d5ac00497a..4cf8523ad0381a50eed016607877826899824b59 100644 (file)
--- a/fs/smb/server/vfs.c
+++ b/fs/smb/server/vfs.c
@@ -708,6 +708,10 @@ retry:
                goto out2;
 
        trap = lock_rename_child(old_child, new_path.dentry);
                goto out2;
 
        trap = lock_rename_child(old_child, new_path.dentry);

+       if (IS_ERR(trap)) {
+               err = PTR_ERR(trap);
+               goto out_drop_write;
+       }

 
        old_parent = dget(old_child->d_parent);
        if (d_unhashed(old_child)) {
 
        old_parent = dget(old_child->d_parent);
        if (d_unhashed(old_child)) {


@@ -770,6 +774,7 @@ out4:
 out3:
        dput(old_parent);
        unlock_rename(old_parent, new_path.dentry);
 out3:
        dput(old_parent);
        unlock_rename(old_parent, new_path.dentry);

+out_drop_write:

        mnt_drop_write(old_path->mnt);
 out2:
        path_put(&new_path);
        mnt_drop_write(old_path->mnt);
 out2:
        path_put(&new_path);