ecryptfs: use new start_creating/start_removing APIs

This requires the addition of start_creating_dentry() which is given the
dentry which has already been found, and asks for it to be locked and
its parent validated.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://patch.msgid.link/20251113002050.676694-14-neilb@ownmail.net
Tested-by: syzbot@syzkaller.appspotmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index ed1394da8d6bd7065f2a074378331f13fcda17f9..6a5bca89e752ed6eeb1cb64c7bd97b4bc0d93323 100644 (file)
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -24,18 +24,26 @@
 #include <linux/unaligned.h>
 #include "ecryptfs_kernel.h"
 
-static int lock_parent(struct dentry *dentry,
-                      struct dentry **lower_dentry,
-                      struct inode **lower_dir)
+static struct dentry *ecryptfs_start_creating_dentry(struct dentry *dentry)
 {
-       struct dentry *lower_dir_dentry;
+       struct dentry *parent = dget_parent(dentry);
+       struct dentry *ret;
 
-       lower_dir_dentry = ecryptfs_dentry_to_lower(dentry->d_parent);
-       *lower_dir = d_inode(lower_dir_dentry);
-       *lower_dentry = ecryptfs_dentry_to_lower(dentry);
+       ret = start_creating_dentry(ecryptfs_dentry_to_lower(parent),
+                                   ecryptfs_dentry_to_lower(dentry));
+       dput(parent);
+       return ret;
+}
 
-       inode_lock_nested(*lower_dir, I_MUTEX_PARENT);
-       return (*lower_dentry)->d_parent == lower_dir_dentry ? 0 : -EINVAL;
+static struct dentry *ecryptfs_start_removing_dentry(struct dentry *dentry)
+{
+       struct dentry *parent = dget_parent(dentry);
+       struct dentry *ret;
+
+       ret = start_removing_dentry(ecryptfs_dentry_to_lower(parent),
+                                   ecryptfs_dentry_to_lower(dentry));
+       dput(parent);
+       return ret;
 }
 
 static int ecryptfs_inode_test(struct inode *inode, void *lower_inode)
@@ -141,15 +149,12 @@ static int ecryptfs_do_unlink(struct inode *dir, struct dentry *dentry,
        struct inode *lower_dir;
        int rc;
 
-       rc = lock_parent(dentry, &lower_dentry, &lower_dir);
-       dget(lower_dentry);     // don't even try to make the lower negative
-       if (!rc) {
-               if (d_unhashed(lower_dentry))
-                       rc = -EINVAL;
-               else
-                       rc = vfs_unlink(&nop_mnt_idmap, lower_dir, lower_dentry,
-                                       NULL);
-       }
+       lower_dentry = ecryptfs_start_removing_dentry(dentry);
+       if (IS_ERR(lower_dentry))
+               return PTR_ERR(lower_dentry);
+
+       lower_dir = lower_dentry->d_parent->d_inode;
+       rc = vfs_unlink(&nop_mnt_idmap, lower_dir, lower_dentry, NULL);
        if (rc) {
                printk(KERN_ERR "Error in vfs_unlink; rc = [%d]\n", rc);
                goto out_unlock;
@@ -158,8 +163,7 @@ static int ecryptfs_do_unlink(struct inode *dir, struct dentry *dentry,
        set_nlink(inode, ecryptfs_inode_to_lower(inode)->i_nlink);
        inode_set_ctime_to_ts(inode, inode_get_ctime(dir));
 out_unlock:
-       dput(lower_dentry);
-       inode_unlock(lower_dir);
+       end_removing(lower_dentry);
        if (!rc)
                d_drop(dentry);
        return rc;
@@ -186,10 +190,12 @@ ecryptfs_do_create(struct inode *directory_inode,
        struct inode *lower_dir;
        struct inode *inode;
 
-       rc = lock_parent(ecryptfs_dentry, &lower_dentry, &lower_dir);
-       if (!rc)
-               rc = vfs_create(&nop_mnt_idmap, lower_dir,
-                               lower_dentry, mode, true);
+       lower_dentry = ecryptfs_start_creating_dentry(ecryptfs_dentry);
+       if (IS_ERR(lower_dentry))
+               return ERR_CAST(lower_dentry);
+       lower_dir = lower_dentry->d_parent->d_inode;
+       rc = vfs_create(&nop_mnt_idmap, lower_dir,
+                       lower_dentry, mode, true);
        if (rc) {
                printk(KERN_ERR "%s: Failure to create dentry in lower fs; "
                       "rc = [%d]\n", __func__, rc);
@@ -205,7 +211,7 @@ ecryptfs_do_create(struct inode *directory_inode,
        fsstack_copy_attr_times(directory_inode, lower_dir);
        fsstack_copy_inode_size(directory_inode, lower_dir);
 out_lock:
-       inode_unlock(lower_dir);
+       end_creating(lower_dentry, NULL);
        return inode;
 }
 
@@ -433,10 +439,12 @@ static int ecryptfs_link(struct dentry *old_dentry, struct inode *dir,
 
        file_size_save = i_size_read(d_inode(old_dentry));
        lower_old_dentry = ecryptfs_dentry_to_lower(old_dentry);
-       rc = lock_parent(new_dentry, &lower_new_dentry, &lower_dir);
-       if (!rc)
-               rc = vfs_link(lower_old_dentry, &nop_mnt_idmap, lower_dir,
-                             lower_new_dentry, NULL);
+       lower_new_dentry = ecryptfs_start_creating_dentry(new_dentry);
+       if (IS_ERR(lower_new_dentry))
+               return PTR_ERR(lower_new_dentry);
+       lower_dir = lower_new_dentry->d_parent->d_inode;
+       rc = vfs_link(lower_old_dentry, &nop_mnt_idmap, lower_dir,
+                     lower_new_dentry, NULL);
        if (rc || d_really_is_negative(lower_new_dentry))
                goto out_lock;
        rc = ecryptfs_interpose(lower_new_dentry, new_dentry, dir->i_sb);
@@ -448,7 +456,7 @@ static int ecryptfs_link(struct dentry *old_dentry, struct inode *dir,
                  ecryptfs_inode_to_lower(d_inode(old_dentry))->i_nlink);
        i_size_write(d_inode(new_dentry), file_size_save);
 out_lock:
-       inode_unlock(lower_dir);
+       end_creating(lower_new_dentry, NULL);
        return rc;
 }
 
@@ -468,9 +476,11 @@ static int ecryptfs_symlink(struct mnt_idmap *idmap,
        size_t encoded_symlen;
        struct ecryptfs_mount_crypt_stat *mount_crypt_stat = NULL;
 
-       rc = lock_parent(dentry, &lower_dentry, &lower_dir);
-       if (rc)
-               goto out_lock;
+       lower_dentry = ecryptfs_start_creating_dentry(dentry);
+       if (IS_ERR(lower_dentry))
+               return PTR_ERR(lower_dentry);
+       lower_dir = lower_dentry->d_parent->d_inode;
+
        mount_crypt_stat = &ecryptfs_superblock_to_private(
                dir->i_sb)->mount_crypt_stat;
        rc = ecryptfs_encrypt_and_encode_filename(&encoded_symname,
@@ -490,7 +500,7 @@ static int ecryptfs_symlink(struct mnt_idmap *idmap,
        fsstack_copy_attr_times(dir, lower_dir);
        fsstack_copy_inode_size(dir, lower_dir);
 out_lock:
-       inode_unlock(lower_dir);
+       end_creating(lower_dentry, NULL);
        if (d_really_is_negative(dentry))
                d_drop(dentry);
        return rc;
@@ -501,12 +511,14 @@ static struct dentry *ecryptfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 {
        int rc;
        struct dentry *lower_dentry;
+       struct dentry *lower_dir_dentry;
        struct inode *lower_dir;
 
-       rc = lock_parent(dentry, &lower_dentry, &lower_dir);
-       if (rc)
-               goto out;
-
+       lower_dentry = ecryptfs_start_creating_dentry(dentry);
+       if (IS_ERR(lower_dentry))
+               return lower_dentry;
+       lower_dir_dentry = dget(lower_dentry->d_parent);
+       lower_dir = lower_dir_dentry->d_inode;
        lower_dentry = vfs_mkdir(&nop_mnt_idmap, lower_dir,
                                 lower_dentry, mode);
        rc = PTR_ERR(lower_dentry);
@@ -522,7 +534,7 @@ static struct dentry *ecryptfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
        fsstack_copy_inode_size(dir, lower_dir);
        set_nlink(dir, lower_dir->i_nlink);
 out:
-       inode_unlock(lower_dir);
+       end_creating(lower_dentry, lower_dir_dentry);
        if (d_really_is_negative(dentry))
                d_drop(dentry);
        return ERR_PTR(rc);
@@ -534,21 +546,18 @@ static int ecryptfs_rmdir(struct inode *dir, struct dentry *dentry)
        struct inode *lower_dir;
        int rc;
 
-       rc = lock_parent(dentry, &lower_dentry, &lower_dir);
-       dget(lower_dentry);     // don't even try to make the lower negative
-       if (!rc) {
-               if (d_unhashed(lower_dentry))
-                       rc = -EINVAL;
-               else
-                       rc = vfs_rmdir(&nop_mnt_idmap, lower_dir, lower_dentry);
-       }
+       lower_dentry = ecryptfs_start_removing_dentry(dentry);
+       if (IS_ERR(lower_dentry))
+               return PTR_ERR(lower_dentry);
+       lower_dir = lower_dentry->d_parent->d_inode;
+
+       rc = vfs_rmdir(&nop_mnt_idmap, lower_dir, lower_dentry);
        if (!rc) {
                clear_nlink(d_inode(dentry));
                fsstack_copy_attr_times(dir, lower_dir);
                set_nlink(dir, lower_dir->i_nlink);
        }
-       dput(lower_dentry);
-       inode_unlock(lower_dir);
+       end_removing(lower_dentry);
        if (!rc)
                d_drop(dentry);
        return rc;
@@ -562,10 +571,12 @@ ecryptfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
        struct dentry *lower_dentry;
        struct inode *lower_dir;
 
-       rc = lock_parent(dentry, &lower_dentry, &lower_dir);
-       if (!rc)
-               rc = vfs_mknod(&nop_mnt_idmap, lower_dir,
-                              lower_dentry, mode, dev);
+       lower_dentry = ecryptfs_start_creating_dentry(dentry);
+       if (IS_ERR(lower_dentry))
+               return PTR_ERR(lower_dentry);
+       lower_dir = lower_dentry->d_parent->d_inode;
+
+       rc = vfs_mknod(&nop_mnt_idmap, lower_dir, lower_dentry, mode, dev);
        if (rc || d_really_is_negative(lower_dentry))
                goto out;
        rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb);
@@ -574,7 +585,7 @@ ecryptfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
        fsstack_copy_attr_times(dir, lower_dir);
        fsstack_copy_inode_size(dir, lower_dir);
 out:
-       inode_unlock(lower_dir);
+       end_removing(lower_dentry);
        if (d_really_is_negative(dentry))
                d_drop(dentry);
        return rc;
@@ -590,7 +601,6 @@ ecryptfs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
        struct dentry *lower_new_dentry;
        struct dentry *lower_old_dir_dentry;
        struct dentry *lower_new_dir_dentry;
-       struct dentry *trap;
        struct inode *target_inode;
        struct renamedata rd = {};
 
@@ -605,31 +615,13 @@ 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);
-       if (IS_ERR(trap))
-               return PTR_ERR(trap);
-       dget(lower_new_dentry);
-       rc = -EINVAL;
-       if (lower_old_dentry->d_parent != lower_old_dir_dentry)
-               goto out_lock;
-       if (lower_new_dentry->d_parent != lower_new_dir_dentry)
-               goto out_lock;
-       if (d_unhashed(lower_old_dentry) || d_unhashed(lower_new_dentry))
-               goto out_lock;
-       /* source should not be ancestor of target */
-       if (trap == lower_old_dentry)
-               goto out_lock;
-       /* target should not be ancestor of source */
-       if (trap == lower_new_dentry) {
-               rc = -ENOTEMPTY;
-               goto out_lock;
-       }
+       rd.mnt_idmap  = &nop_mnt_idmap;
+       rd.old_parent = lower_old_dir_dentry;
+       rd.new_parent = lower_new_dir_dentry;
+       rc = start_renaming_two_dentries(&rd, lower_old_dentry, lower_new_dentry);
+       if (rc)
+               return rc;
 
-       rd.mnt_idmap            = &nop_mnt_idmap;
-       rd.old_parent           = lower_old_dir_dentry;
-       rd.old_dentry           = lower_old_dentry;
-       rd.new_parent           = lower_new_dir_dentry;
-       rd.new_dentry           = lower_new_dentry;
        rc = vfs_rename(&rd);
        if (rc)
                goto out_lock;
@@ -640,8 +632,7 @@ ecryptfs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
        if (new_dir != old_dir)
                fsstack_copy_attr_all(old_dir, d_inode(lower_old_dir_dentry));
 out_lock:
-       dput(lower_new_dentry);
-       unlock_rename(lower_old_dir_dentry, lower_new_dir_dentry);
+       end_renaming(&rd);
        return rc;
 }
 

diff --git a/fs/namei.c b/fs/namei.c
index 4a4b8b96c1927544114c2a747d7d9bcc6228a45b..8b7807cd1343d30250adf8bb953177749b1da6fa 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3397,6 +3397,39 @@ struct dentry *start_removing_noperm(struct dentry *parent,
 }
 EXPORT_SYMBOL(start_removing_noperm);
 
+/**
+ * start_creating_dentry - prepare to create a given dentry
+ * @parent: directory from which dentry should be removed
+ * @child:  the dentry to be removed
+ *
+ * A lock is taken to protect the dentry again other dirops and
+ * the validity of the dentry is checked: correct parent and still hashed.
+ *
+ * If the dentry is valid and negative a reference is taken and
+ * returned.  If not an error is returned.
+ *
+ * end_creating() should be called when creation is complete, or aborted.
+ *
+ * Returns: the valid dentry, or an error.
+ */
+struct dentry *start_creating_dentry(struct dentry *parent,
+                                    struct dentry *child)
+{
+       inode_lock_nested(parent->d_inode, I_MUTEX_PARENT);
+       if (unlikely(IS_DEADDIR(parent->d_inode) ||
+                    child->d_parent != parent ||
+                    d_unhashed(child))) {
+               inode_unlock(parent->d_inode);
+               return ERR_PTR(-EINVAL);
+       }
+       if (d_is_positive(child)) {
+               inode_unlock(parent->d_inode);
+               return ERR_PTR(-EEXIST);
+       }
+       return dget(child);
+}
+EXPORT_SYMBOL(start_creating_dentry);
+
 /**
  * start_removing_dentry - prepare to remove a given dentry
  * @parent: directory from which dentry should be removed

diff --git a/include/linux/namei.h b/include/linux/namei.h
index a99ac8b7e24a23989a6f347d32e7a51f206d2122..208aed1d67283331fcf973eccba83607ed3a7237 100644 (file)
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -100,6 +100,8 @@ struct dentry *start_removing_killable(struct mnt_idmap *idmap,
                                       struct qstr *name);
 struct dentry *start_creating_noperm(struct dentry *parent, struct qstr *name);
 struct dentry *start_removing_noperm(struct dentry *parent, struct qstr *name);
+struct dentry *start_creating_dentry(struct dentry *parent,
+                                    struct dentry *child);
 struct dentry *start_removing_dentry(struct dentry *parent,
                                     struct dentry *child);