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From: NeilBrown <neilb@suse.de>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
	Jonathan Corbet <corbet@lwn.net>, Xin Long <lucien.xin@gmail.com>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Vlad Yasevich <vyasevich@gmail.com>,
	Neil Horman <nhorman@tuxdriver.com>,
	Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	linux-sctp@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH 0/3] Fix some seq_file users that were recently broken
Date: Mon, 08 Feb 2021 09:45:09 +1100	[thread overview]
Message-ID: <87ft27ebuy.fsf@notabene.neil.brown.name> (raw)
In-Reply-To: <20210205143550.58d3530918459eafa918ad0c@linux-foundation.org>

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On Fri, Feb 05 2021, Andrew Morton wrote:

> On Fri, 05 Feb 2021 11:36:30 +1100 NeilBrown <neilb@suse.de> wrote:
>
>> A recent change to seq_file broke some users which were using seq_file
>> in a non-"standard" way ...  though the "standard" isn't documented, so
>> they can be excused.  The result is a possible leak - of memory in one
>> case, of references to a 'transport' in the other.
>> 
>> These three patches:
>>  1/ document and explain the problem
>>  2/ fix the problem user in x86
>>  3/ fix the problem user in net/sctp
>> 
>
> 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code and
> interface") was August 2018, so I don't think "recent" applies here?

I must be getting old :-(

>
> I didn't look closely, but it appears that the sctp procfs file is
> world-readable.  So we gave unprivileged userspace the ability to leak
> kernel memory?

Not quite that bad.  The x86 problem allows arbitrary memory to be
leaked, but that is in debugfs (as I'm sure you saw) so is root-only.
The sctp one only allows an sctp_transport to be pinned.  That is not
good and would, e.g., prevent the module from being unloaded.  But
unlike a simple memory leak it won't affect anything outside of sctp.

>
> So I'm thinking that we aim for 5.12-rc1 on all three patches with a cc:stable?

Thanks for looking after these!

NeilBrown

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      parent reply	other threads:[~2021-02-07 22:47 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-05  0:36 [PATCH 0/3] Fix some seq_file users that were recently broken NeilBrown
2021-02-05  0:36 ` [PATCH 2/3] x86: fix seq_file iteration for pat/memtype.c NeilBrown
2021-02-05  0:36 ` [PATCH 1/3] seq_file: document how per-entry resources are managed NeilBrown
2021-02-05  2:20   ` Matthew Wilcox
2021-02-05  0:36 ` [PATCH 3/3] net: fix iteration for sctp transport seq_files NeilBrown
2021-02-05 14:32   ` Marcelo Ricardo Leitner
2021-02-05 22:35 ` [PATCH 0/3] Fix some seq_file users that were recently broken Andrew Morton
2021-02-06 22:29   ` Jakub Kicinski
2021-02-07 21:11     ` Andrew Morton
2021-02-08 19:42       ` Jakub Kicinski
2021-02-07 22:45   ` NeilBrown [this message]

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