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: <20231110110002.7279f895@kernel.org>
Date: Fri, 10 Nov 2023 11:00:02 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: "Jong eon Park" <jongeon.park@...sung.com>
Cc: "'Paolo Abeni'" <pabeni@...hat.com>, "'David S. Miller'"
 <davem@...emloft.net>, "'Eric Dumazet'" <edumazet@...gle.com>,
 <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>, "'Dong ha Kang'"
 <dongha7.kang@...sung.com>
Subject: Re: [PATCH] netlink: introduce netlink poll to resolve fast return
 issue

On Fri, 10 Nov 2023 23:54:48 +0900 Jong eon Park wrote:
> Interestingly, in this issue, even though netlink overrun frequently 
> happened and caused POLLERRs, the user was managing it well through 
> POLLIN and 'recv' function without a specific POLLERR handler. 
> However, in the current situation, rcv queue is already empty and 
> NETLINK_S_CONGESTED flag prevents any more incoming packets. This makes 
> it impossible for the user to call 'recv'.
> 
> This "congested" situation is a bit ambiguous. The queue is empty, yet 
> 'congested' remains. This means kernel can no longer deliver uevents 
> despite the empty queue, and it lead to the persistent 'congested' status.
> 
> The reason for the difference in netlink lies in the NETLINK_S_CONGESTED 
> flag. If it were UDP, upon seeing the empty queue, it might have kept 
> pushing the received packets into the queue (making possible to call 
> 'recv').

I see, please add a comment saying that NETLINK_S_CONGESTED prevents
new skbs from being queued before the new test in netlink_poll().

Please repost next week (i.e. after the merge window) with subject
tagged [PATCH net-next v2].

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ