[linux-cifs-client] [RFC][PATCH] cifs: fix potential cifsFileInfo struct leaks

[Suresh Jayaraman]

On 05/10/2010 07:30 PM, Shirish Pargaonkar wrote:
> On Mon, May 10, 2010 at 6:51 AM, Suresh Jayaraman <sjayaraman at suse.de> wrote:
>> cifs_new_fileinfo() allocates and return a pointer to a struct cifsFileInfo
>> based on which file->private_data is set. Apparently, we seem to be leaking
>> cifsFileInfo structs when called from cifs_posix_open and cifs_create as we
>> ignore the return value.
>>
>> IIUC, if we are unable to set file->private_data, then there seem to be little
>> use in calling cifs_new_fileinfo(). Since the file pointer being passed is
>> always NULL when called from both the callers, remove the call to
>> cifs_new_fileinfo which seems to be of no use.
>>
>> This patch needs careful review.
>>
>> Signed-off-by: Suresh Jayaraman <sjayaraman at suse.de>
>> ---
>> �fs/cifs/dir.c | � 10 ++--------
>> �1 files changed, 2 insertions(+), 8 deletions(-)
>>
>> diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
>> index d791d07..046f0a7 100644
>> --- a/fs/cifs/dir.c
>> +++ b/fs/cifs/dir.c
>> @@ -251,9 +251,6 @@ int cifs_posix_open(char *full_path, struct inode **pinode,
>> � � � � � � � �cifs_fattr_to_inode(*pinode, &fattr);
>> � � � �}
>>
>> - � � � if (mnt)
>> - � � � � � � � cifs_new_fileinfo(*pinode, *pnetfid, NULL, mnt, oflags);
>> -
>> �posix_open_ret:
>> � � � �kfree(presp_data);
>> � � � �return rc;
>> @@ -462,13 +459,10 @@ cifs_create_set_dentry:
>> � � � � � � � �cFYI(1, "Create worked, get_inode_info failed rc = %d", rc);
>>
>> � � � �/* nfsd case - nfs srv does not set nd */
>> - � � � if ((nd == NULL) || (!(nd->flags & LOOKUP_OPEN))) {
>> + � � � if ((nd == NULL) || (!(nd->flags & LOOKUP_OPEN)))
>> � � � � � � � �/* mknod case - do not leave file open */
>> � � � � � � � �CIFSSMBClose(xid, tcon, fileHandle);
>> - � � � } else if (!(posix_create) && (newinode)) {
>> - � � � � � � � � � � � cifs_new_fileinfo(newinode, fileHandle, NULL,
>> - � � � � � � � � � � � � � � � � � � � � � � � nd->path.mnt, oflags);
>> - � � � }
>> +
>> �cifs_create_out:
>> � � � �kfree(buf);
>> � � � �kfree(full_path);
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>>
> 
> We should not do this.
> In case of cifs_create/cifs_lookup, even though the retrun value of
> cifs_new_fileinfo is assigned directly,
> because we do not have file structure at that point, pcifsFileInfo is
> stuck on the openFileList and
> pcifsFileInfo gets discovered in cifs_open is assigned to file's
> private data in cifs_fill_filedata.
> 

Yes, I see what you explained, quite hideous.. I'll roll up a doc patch
explaining it a bit more clear..

But I'm not sure whether there is a race window that exists, though. I'm
trying to track a infamous "VFS: Busy inodes after unmount" error..



Thanks,

-- 
Suresh Jayaraman