linux-kernel - [PATCH 5.9 536/757] nfsd: Cache R, RW, and W opens separately

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Date:   Tue, 27 Oct 2020 14:53:06 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Chuck Lever <chuck.lever@...cle.com>,
        "J. Bruce Fields" <bfields@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.9 536/757] nfsd: Cache R, RW, and W opens separately

From: J. Bruce Fields <bfields@...hat.com>

[ Upstream commit ae3c57b5ca47665dc3416447a5534a9796096d86 ]

The nfsd open code has always kept separate read-only, read-write, and
write-only opens as necessary to ensure that when a client closes or
downgrades, we don't retain more access than necessary.

Also, I didn't realize the cache behaved this way when I wrote
94415b06eb8a "nfsd4: a client's own opens needn't prevent delegations".
There I assumed fi_fds[O_WRONLY] and fi_fds[O_RDWR] would always be
distinct.  The violation of that assumption is triggering a
WARN_ON_ONCE() and could also cause the server to give out a delegation
when it shouldn't.

Fixes: 94415b06eb8a ("nfsd4: a client's own opens needn't prevent delegations")
Tested-by: Chuck Lever <chuck.lever@...cle.com>
Signed-off-by: J. Bruce Fields <bfields@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/nfsd/filecache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index c8b9d2667ee6f..3c6c2f7d1688b 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -889,7 +889,7 @@ nfsd_file_find_locked(struct inode *inode, unsigned int may_flags,

 	hlist_for_each_entry_rcu(nf, &nfsd_file_hashtbl[hashval].nfb_head,
 				 nf_node, lockdep_is_held(&nfsd_file_hashtbl[hashval].nfb_lock)) {
-		if ((need & nf->nf_may) != need)
+		if (nf->nf_may != need)
 			continue;
 		if (nf->nf_inode != inode)
 			continue;
-- 
2.25.1