Attachment 4640 Details for Bug 6651 – Hopefully last part of the fix...

[patch] Hopefully last part of the fix...

0002-Hopefully-last-part-of-the-fix-for-bug-6651-smbd-S.patch (text/plain), 2.25 KB, created by Jeremy Allison on 2009-09-03 09:59:52 UTC

(hide)

Description:

Filename:

MIME Type:

Creator: Jeremy Allison

Created: 2009-09-03 09:59:52 UTC

Size: 2.25 KB

patch

obsolete

>From bdc7bdb0d3e02d04477906dbda8995bc5789ce22 Mon Sep 17 00:00:00 2001
>From: Jeremy Allison <jra@samba.org>
>Date: Thu, 3 Sep 2009 07:40:48 -0700
>Subject: [PATCH] Hopefully last part of the fix for bug 6651 - smbd SIGSEGV when breaking oplocks.
> This one is subtle. There is a race condition where a signal can be
> queued for oplock break, and then the file can be closed by the client
> before the signal can be processed. Currently if this occurs we panic
> (we can't match an incoming signal fd with a fsp pointer). Simply log
> the error (at debug level 10 right now, might be too much) and then
> return without processing the break request. It looks like there is
> another race condition with this fix, but here's why it won't happen.
> If the signal was pending (caused by a kernel oplock break from a
> local file open), and the client closed the file and then re-opened
> another file which happened to use the same file descriptor as the
> file just closed, then theoretically the oplock break requests could
> be processed on the wrong fd. Here's why this should be very rare..
> Processing a pending signal always take precedence over an incoming
> network request, so as long as the client close request is non-chained
> then the break signal should always be harmlessly processed *before*
> the open can be called. If the open is chained onto the close, and
> the fd on the new open is the same as the old closed fd, then it's
> possible this race will occur. However, all that will happen is that
> we'll lose the oplock on this file. A shame, but not a fatal event.
> Jeremy.
>
>---
> source3/smbd/oplock_linux.c |    4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/source3/smbd/oplock_linux.c b/source3/smbd/oplock_linux.c
>index 535e809..c60c745 100644
>--- a/source3/smbd/oplock_linux.c
>+++ b/source3/smbd/oplock_linux.c
>@@ -99,8 +99,8 @@ static void linux_oplock_signal_handler(struct tevent_context *ev_ctx,
> 
> 	fsp = file_find_fd(fd);
> 	if (fsp == NULL) {
>-		DEBUG(0,("linux_oplock_signal_handler: failed to find fsp for file fd=%d\n", fd ));
>-		smb_panic("linux_oplock_signal_handler\n");
>+		DEBUG(0,("linux_oplock_signal_handler: failed to find fsp for file fd=%d (file was closed ?)\n", fd ));
>+		return;
> 	}
> 	break_kernel_oplock(smbd_messaging_context(), fsp);
> }
>-- 
>1.6.0.4
>

Actions: View

Attachments on bug 6651: 4580 | 4585 | 4586 | 4595 | 4639 | 4640 | 4647