mirror of
https://github.com/torvalds/linux.git
synced 2026-05-05 23:05:25 -04:00
0a55cf74ff
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: 8de9e86c67 ("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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.