From: Steve French stfrench@microsoft.com
commit 0a55cf74ffb5d004b93647e4389096880ce37d6b upstream.
There is a race condition in smb2_compound_op:
after_close: num_rqst++;
if (cfile) { cifsFileInfo_put(cfile); // sends SMB2_CLOSE to the server cfile = NULL;
This is triggered by smb2_query_path_info operation that happens during revalidate_dentry. In smb2_query_path_info, get_readable_path is called to load the cfile, increasing the reference counter. If in the meantime, this reference becomes the very last, this call to cifsFileInfo_put(cfile) will trigger a SMB2_CLOSE request sent to the server just before sending this compound request – and so then the compound request fails either with EBADF/EIO depending on the timing at the server, because the handle is already closed.
In the first scenario, the race seems to be happening between smb2_query_path_info triggered by the rename operation, and between “cleanup” of asynchronous writes – while fsync(fd) likely waits for the asynchronous writes to complete, releasing the writeback structures can happen after the close(fd) call. So the EBADF/EIO errors will pop up if the timing is such that: 1) There are still outstanding references after close(fd) in the writeback structures 2) smb2_query_path_info successfully fetches the cfile, increasing the refcounter by 1 3) All writeback structures release the same cfile, reducing refcounter to 1 4) smb2_compound_op is called with that cfile
In the second scenario, the race seems to be similar – here open triggers the smb2_query_path_info operation, and if all other threads in the meantime decrease the refcounter to 1 similarly to the first scenario, again SMB2_CLOSE will be sent to the server just before issuing the compound request. This case is harder to reproduce.
See https://bugzilla.samba.org/show_bug.cgi?id=15051
Cc: stable@vger.kernel.org Fixes: 8de9e86c67ba ("cifs: create a helper to find a writeable handle by path name") Signed-off-by: Ondrej Hubsch ohubsch@purestorage.com Reviewed-by: Ronnie Sahlberg lsahlber@redhat.com Reviewed-by: Paulo Alcantara (SUSE) pc@cjr.nz Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/cifs/smb2inode.c | 2 -- 1 file changed, 2 deletions(-)
--- a/fs/cifs/smb2inode.c +++ b/fs/cifs/smb2inode.c @@ -358,8 +358,6 @@ smb2_compound_op(const unsigned int xid, num_rqst++;
if (cfile) { - cifsFileInfo_put(cfile); - cfile = NULL; rc = compound_send_recv(xid, ses, server, flags, num_rqst - 2, &rqst[1], &resp_buftype[1],