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Date:   Thu, 28 Jan 2021 17:36:38 -0500
To:     Anna Schumaker <schumakeranna@gmail.com>,
        Trond Myklebust <trondmy@hammerspace.com>
Cc:     linux-nfs@vger.kernel.org
Subject: [PATCH] nfs: we don't support removing system.nfs4_acl
Message-ID: <20210128223638.GE29887@fieldses.org>
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From:   bfields@fieldses.org (J. Bruce Fields)
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From: "J. Bruce Fields" <bfields@redhat.com>

The NFSv4 protocol doesn't have any notion of reomoving an attribute, so
removexattr(path,"system.nfs4_acl") doesn't make sense.

There's no documented return value.  Arguably it could be EOPNOTSUPP but
I'm a little worried an application might take that to mean that we
don't support ACLs or xattrs.  How about EINVAL?

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
 fs/nfs/nfs4proc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 2f4679a62712..d50dea5f5723 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5895,6 +5895,9 @@ static int __nfs4_proc_set_acl(struct inode *inode, const void *buf, size_t bufl
 	unsigned int npages = DIV_ROUND_UP(buflen, PAGE_SIZE);
 	int ret, i;
 
+	/* You can't remove system.nfs4_acl: */
+	if (buflen == 0)
+		return -EINVAL;
 	if (!nfs4_server_supports_acls(server))
 		return -EOPNOTSUPP;
 	if (npages > ARRAY_SIZE(pages))
-- 
2.29.2