netdev - Re: [PATCH v2 0/4] nfsd/sunrpc: cleanup resource with sync mode

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Message-ID: <173514289446.295832.15514335628536963233.b4-ty@oracle.com>
Date: Wed, 25 Dec 2024 11:13:41 -0500
From: cel@...nel.org
To: jlayton@...nel.org,
	neilb@...e.de,
	okorniev@...hat.com,
	Dai.Ngo@...cle.com,
	tom@...pey.com,
	trondmy@...nel.org,
	anna@...nel.org,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	horms@...nel.org,
	Yang Erkun <yangerkun@...wei.com>
Cc: Chuck Lever <chuck.lever@...cle.com>,
	linux-nfs@...r.kernel.org,
	netdev@...r.kernel.org,
	yangerkun@...weicloud.com,
	liumingrui@...wei.com
Subject: Re: [PATCH v2 0/4] nfsd/sunrpc: cleanup resource with sync mode

From: Chuck Lever <chuck.lever@...cle.com>

On Wed, 25 Dec 2024 14:59:04 +0800, Yang Erkun wrote:
> After f8c989a0c89a ("nfsd: release svc_expkey/svc_export with
> rcu_work"), svc_export_put/expkey_put will call path_put with async
> mode. This can lead some unexpected failure:
> 
> mkdir /mnt/sda
> mkfs.xfs -f /dev/sda
> echo "/ *(rw,no_root_squash,fsid=0)" > /etc/exports
> echo "/mnt *(rw,no_root_squash,fsid=1)" >> /etc/exports
> exportfs -ra
> service nfs-server start
> mount -t nfs -o vers=4.0 127.0.0.1:/mnt /mnt1
> mount /dev/sda /mnt/sda
> touch /mnt1/sda/file
> exportfs -r
> umount /mnt/sda # failed unexcepted
> 
> [...]

Applied to nfsd-testing for v6.14, thanks!

I'm unsure whether 2/4 and 3/4 need Fixes: tags. Based on the patch
descriptions, these appear to be pre-requisite patches rather than
actual fixes.

However, I'm guessing that 4/4 will apply and build without 2/4 and
3/4 applied, but there will be operational problems. So explicit
Fixes: tags in 2/4 and 3/4 are probably necessary to get a properly
working backport.

This is a case where I would rather have manual backporting with
a full CI run rather than just slapping these patches on the LTS
kernels and hoping for the best.

[1/4] SUNRPC: introduce cache_check_rcu to help check in rcu context
      commit: 401fd94cb21c978403077d611bdc311dc8376f9d
[2/4] nfsd: no need get cache ref when protected by rcu
      commit: 3d32486aa35bf4b99edbfc27538b24fadebd7f75
[3/4] SUNRPC: no need get cache ref when protected by rcu
      commit: 9f5fc67903b5709c4334bf33764d6fbf0ceb05b4
[4/4] nfsd: fix UAF when access ex_uuid or ex_stats
      commit: 8fa5adbee5ab904ea282da183ece664a67db2b2b

--
Chuck Lever