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Subject[PATCH 5.1 013/121] cifs: add spinlock for the openFileList to cifsInodeInfo
Date
From: Ronnie Sahlberg <lsahlber@redhat.com>

commit 487317c99477d00f22370625d53be3239febabbe upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/cifs/cifsfs.c | 1 +
fs/cifs/cifsglob.h | 5 +++++
fs/cifs/file.c | 8 ++++++--
3 files changed, 12 insertions(+), 2 deletions(-)

--- 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);

/*
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1357,6 +1357,7 @@ 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 */
@@ -1760,10 +1761,14 @@ 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
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -338,10 +338,12 @@ cifs_new_fileinfo(struct cifs_fid *fid,
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 cifsFileIn
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;

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