netdev - RE: [PATCH] net: Fix race condition on receive path.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1267832667.30393.16.camel@c-dwalke-linux.qualcomm.com>
Date:	Fri, 05 Mar 2010 15:44:27 -0800
From:	Daniel Walker <dwalker@...eaurora.org>
To:	"Harford, Jim" <c_jharfo@...cinc.com>
Cc:	Stephen Hemminger <shemminger@...tta.com>,
	"David S. Miller" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Smith, Alan" <agsmith@...cinc.com>
Subject: RE: [PATCH] net: Fix race condition on receive path.

On Fri, 2010-03-05 at 15:41 -0800, Harford, Jim wrote:
> It appears that this patch is no longer necessary.  It was made against 2.6.29, but I see that more recent kernel versions don't have the problem code.  For a more detailed explanation, see below.  All code references are in routine process_backlog(), file net/core/dev.c.
> 
> In kernel version 2.6.27.45, __napi_complete() is invoked BEFORE interrupts are re-enabled.  Thus, the receive queue status is cleaned up before another interrupt (due to a receive packet) can occur.  This is good design.
> 
> In kernel version 2.6.29, git commit ID 303c6a025 inverts this ordering.  Routine napi_complete() is invoked AFTER interrupts are re-enabled.  We observed interrupts taken after interrupts were re-enabled, but before napi_complete cleaned up the receive queue.  This would then shut down the processing of subsequent received packets.
> 
> In kernel versions 2.6.30.10 and later, the sequence of operations is identical to 2.6.27.45, so there is no problem.
> 
> Jim Harford
> Qualcomm Innovation Center

Ok, I guess we can ignore this one then.

Daniel

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html