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Date:   Mon, 18 Feb 2019 14:43:03 +0100
From:   Greg Kroah-Hartman <>
Cc:     Greg Kroah-Hartman <>,, Chris Perl <>,
        Anna Schumaker <>,
        Sasha Levin <>
Subject: [PATCH 4.4 055/143] NFS: nfs_compare_mount_options always compare auth flavors.

4.4-stable review patch.  If anyone has any objections, please let me know.


[ Upstream commit 594d1644cd59447f4fceb592448d5cd09eb09b5e ]

This patch removes the check from nfs_compare_mount_options to see if a
`sec' option was passed for the current mount before comparing auth
flavors and instead just always compares auth flavors.

Consider the following scenario:

You have a server with the address and two exports /export/a
and /export/b.  The first export supports `sys' and `krb5' security, the
second just `sys'.

Assume you start with no mounts from the server.

The following results in EIOs being returned as the kernel nfs client
incorrectly thinks it can share the underlying `struct nfs_server's:

$ mkdir /tmp/{a,b}
$ sudo mount -t nfs -o vers=3,sec=krb5 /tmp/a
$ sudo mount -t nfs -o vers=3 /tmp/b
$ df >/dev/null
df: ‘/tmp/b’: Input/output error

Signed-off-by: Chris Perl <>
Signed-off-by: Anna Schumaker <>
Signed-off-by: Sasha Levin <>
 fs/nfs/super.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 62f358f67764..412fcfbc50e2 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -2376,8 +2376,7 @@ static int nfs_compare_mount_options(const struct super_block *s, const struct n
 		goto Ebusy;
 	if (a->acdirmax != b->acdirmax)
 		goto Ebusy;
-	if (b->auth_info.flavor_len > 0 &&
-	   clnt_a->cl_auth->au_flavor != clnt_b->cl_auth->au_flavor)
+	if (clnt_a->cl_auth->au_flavor != clnt_b->cl_auth->au_flavor)
 		goto Ebusy;
 	return 1;

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