[PATCH AUTOSEL 3.18 46/61] NFS: nfs_compare_mount_options always compare auth flavors.

Sasha Levin
2019-01-28T16:29:48Z

From: Chris Perl <cperl@janestreet.com>

[ 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 192.168.1.1 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 192.168.1.1:/export/a /tmp/a
$ sudo mount -t nfs -o vers=3 192.168.1.1:/export/b /tmp/b
$ df >/dev/null
df: ‘/tmp/b’: Input/output error

Signed-off-by: Chris Perl <cperl@janestreet.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 dbdc2d2f91cf..655ac3a196e4 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;
Ebusy:
--
2.19.1