cifs: add spinlock for the openFileList to cifsInodeInfo

We can not depend on the tcon->open_file_lock here since in multiuser mode
we may have the same file/inode open via multiple different tcons.

The current code is race prone and will crash if one user deletes a file
at the same time a different user opens/create the file.

To avoid this we need to have a spinlock attached to the inode and not the tcon.

RHBZ:  1580165

CC: Stable <stable@vger.kernel.org>
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index f5fcd63..65d9771 100644 (file)
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -303,6 +303,7 @@ cifs_alloc_inode(struct super_block *sb)
        cifs_inode->uniqueid = 0;
        cifs_inode->createtime = 0;
        cifs_inode->epoch = 0;
+       spin_lock_init(&cifs_inode->open_file_lock);
        generate_random_uuid(cifs_inode->lease_key);
 
        /*

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 334ff5f..4777b3c 100644 (file)
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1377,6 +1377,7 @@ struct cifsInodeInfo {
        struct rw_semaphore lock_sem;   /* protect the fields above */
        /* BB add in lists for dirty pages i.e. write caching info for oplock */
        struct list_head openFileList;
+       spinlock_t      open_file_lock; /* protects openFileList */
        __u32 cifsAttrs; /* e.g. DOS archive bit, sparse, compressed, system */
        unsigned int oplock;            /* oplock/lease level we have */
        unsigned int epoch;             /* used to track lease state changes */
@@ -1780,10 +1781,14 @@ require use of the stronger protocol */
  *  tcp_ses_lock protects:
  *     list operations on tcp and SMB session lists
  *  tcon->open_file_lock protects the list of open files hanging off the tcon
+ *  inode->open_file_lock protects the openFileList hanging off the inode
  *  cfile->file_info_lock protects counters and fields in cifs file struct
  *  f_owner.lock protects certain per file struct operations
  *  mapping->page_lock protects certain per page operations
  *
+ *  Note that the cifs_tcon.open_file_lock should be taken before
+ *  not after the cifsInodeInfo.open_file_lock
+ *
  *  Semaphores
  *  ----------
  *  sesSem     operations on smb session

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 06e27ac..9709069 100644 (file)
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -338,10 +338,12 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
        atomic_inc(&tcon->num_local_opens);
 
        /* if readable file instance put first in list*/
+       spin_lock(&cinode->open_file_lock);
        if (file->f_mode & FMODE_READ)
                list_add(&cfile->flist, &cinode->openFileList);
        else
                list_add_tail(&cfile->flist, &cinode->openFileList);
+       spin_unlock(&cinode->open_file_lock);
        spin_unlock(&tcon->open_file_lock);
 
        if (fid->purge_cache)
@@ -413,7 +415,9 @@ void _cifsFileInfo_put(struct cifsFileInfo *cifs_file, bool wait_oplock_handler)
        cifs_add_pending_open_locked(&fid, cifs_file->tlink, &open);
 
        /* remove it from the lists */
+       spin_lock(&cifsi->open_file_lock);
        list_del(&cifs_file->flist);
+       spin_unlock(&cifsi->open_file_lock);
        list_del(&cifs_file->tlist);
        atomic_dec(&tcon->num_local_opens);
 
@@ -1950,9 +1954,9 @@ refind_writable:
                        return 0;
                }
 
-               spin_lock(&tcon->open_file_lock);
+               spin_lock(&cifs_inode->open_file_lock);
                list_move_tail(&inv_file->flist, &cifs_inode->openFileList);
-               spin_unlock(&tcon->open_file_lock);
+               spin_unlock(&cifs_inode->open_file_lock);
                cifsFileInfo_put(inv_file);
                ++refind;
                inv_file = NULL;