netdev - [PATCH v2 2/4] nfsd: no need get cache ref when protected by rcu

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: <20241225065908.1547645-3-yangerkun@huawei.com>
Date: Wed, 25 Dec 2024 14:59:06 +0800
From: Yang Erkun <yangerkun@...wei.com>
To: chuck.lever@...cle.com,
	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
Cc: linux-nfs@...r.kernel.org,
	netdev@...r.kernel.org,
	yangerkun@...wei.com,
	yangerkun@...weicloud.com,
	liumingrui@...wei.com
Subject: [PATCH v2 2/4] nfsd: no need get cache ref when protected by rcu

rcu_read_lock/rcu_read_unlock has already provide protection for the
pointer we will reference when we call e_show. Therefore, there is no
need to obtain a cache reference to help protect cache_head.
Additionally, the .put such as expkey_put/svc_export_put will invoke
dput, which can sleep and break rcu. Stop get cache reference to fix
them all.

Fixes: ae74136b4bb6 ("SUNRPC: Allow cache lookups to use RCU protection rather than the r/w spinlock")
Suggested-by: NeilBrown <neilb@...e.de>
Signed-off-by: Yang Erkun <yangerkun@...wei.com>
---
 fs/nfsd/export.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index aa4712362b3b..c6168bccfb6c 100644
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -1425,13 +1425,9 @@ static int e_show(struct seq_file *m, void *p)
 		return 0;
 	}
 
-	if (!cache_get_rcu(&exp->h))
+	if (cache_check_rcu(cd, &exp->h, NULL))
 		return 0;
 
-	if (cache_check(cd, &exp->h, NULL))
-		return 0;
-
-	exp_put(exp);
 	return svc_export_show(m, cd, cp);
 }
 
-- 
2.46.1