-----Original Message----- From: Ben Hutchings ben@decadent.org.uk Sent: Wednesday, October 2, 2019 12:07 PM To: linux-kernel@vger.kernel.org; stable@vger.kernel.org Cc: akpm@linux-foundation.org; Denis Kirjanov kda@linux-powerpc.org; Ronnie Sahlberg lsahlber@redhat.com; Steven French Steven.French@microsoft.com; Pavel Shilovskiy pshilov@microsoft.com Subject: [PATCH 3.16 58/87] cifs: add spinlock for the openFileList to cifsInodeInfo
3.16.75-rc1 review patch. If anyone has any objections, please let me know.
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
Signed-off-by: Ronnie Sahlberg lsahlber@redhat.com Signed-off-by: Steve French stfrench@microsoft.com Reviewed-by: Pavel Shilovsky pshilov@microsoft.com [bwh: Backported to 3.16: adjust context, indentation] Signed-off-by: Ben Hutchings ben@decadent.org.uk
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 @@ -260,6 +260,7 @@ 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);
#ifdef CONFIG_CIFS_SMB2 generate_random_uuid(cifs_inode->lease_key); #endif --- a/fs/cifs/cifsglob.h +++ b/fs/cifs/cifsglob.h @@ -1116,6 +1116,7 @@ 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 */ @@ -1485,10 +1486,14 @@ 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 @@ -337,10 +337,12 @@ cifs_new_fileinfo(struct cifs_fid *fid, list_add(&cfile->tlist, &tcon->openFileList);
/* 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) @@ -412,7 +414,9 @@ 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);
if (list_empty(&cifsi->openFileList)) { @@ -1850,10 +1854,10 @@ refind_writable: if (!rc) return inv_file; else {
- 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;
Hi Ben,
We have recently found regressions in this patch that are addressed in the following two patches:
cb248819d209d ("cifs: use cifsInodeInfo->open_file_lock while iterating to avoid a panic") 1a67c41596575 ("CIFS: Fix use after free of file info structures")
So, I would suggest either to apply those two patches above or to revert this one.
-- Best regards, Pavel Shilovsky