linux-kernel - [PATCH v3 4/4] nfs/super: check NFS_CAP

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Message-Id: <20200407142243.2032-4-mk@cm4all.com>
Date:   Tue,  7 Apr 2020 16:22:43 +0200
From:   Max Kellermann <mk@...all.com>
To:     linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
        trond.myklebust@...merspace.com
Cc:     bfields@...hat.com, tytso@....edu, viro@...iv.linux.org.uk,
        agruenba@...hat.com, linux-kernel@...r.kernel.org,
        Max Kellermann <mk@...all.com>, stable@...r.kernel.org
Subject: [PATCH v3 4/4] nfs/super: check NFS_CAP_ACLS instead of the NFS version

This sets SB_POSIXACL only if ACL support is really enabled, instead
of always setting SB_POSIXACL if the NFS protocol version
theoretically supports ACL.

The code comment says "We will [apply the umask] ourselves", but that
happens in posix_acl_create() only if the kernel has POSIX ACL
support.  Without it, posix_acl_create() is an empty dummy function.

So let's not pretend we will apply the umask if we can already know
that we will never.

This fixes a problem where the umask is always ignored in the NFS
client when compiled without CONFIG_FS_POSIX_ACL.  This is a 4 year
old regression caused by commit 013cdf1088d723 which itself was not
completely wrong, but failed to consider all the side effects by
misdesigned VFS code.

Signed-off-by: Max Kellermann <mk@...all.com>
Reviewed-by: J. Bruce Fields <bfields@...hat.com>
Cc: stable@...r.kernel.org
---
 fs/nfs/super.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index dada09b391c6..dab79193f641 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -977,11 +977,14 @@ static void nfs_fill_super(struct super_block *sb, struct nfs_fs_context *ctx)
 	if (ctx && ctx->bsize)
 		sb->s_blocksize = nfs_block_size(ctx->bsize, &sb->s_blocksize_bits);

-	if (server->nfs_client->rpc_ops->version != 2) {
+	if (NFS_SB(sb)->caps & NFS_CAP_ACLS) {
 		/* The VFS shouldn't apply the umask to mode bits. We will do
 		 * so ourselves when necessary.
 		 */
 		sb->s_flags |= SB_POSIXACL;
+	}
+
+	if (server->nfs_client->rpc_ops->version != 2) {
 		sb->s_time_gran = 1;
 		sb->s_export_op = &nfs_export_ops;
 	} else
-- 
2.20.1