For a while now any NFSv2 mount where sec= is specified uses
AUTH_NULL. If sec= is not specified, the mount uses AUTH_UNIX.
Commit e68fd7c8071d ("mount: use sec= that was specified on the
command line") attempted to address a very similar problem with
NFSv3, and should have fixed this too, but it has a bug.
The MNTv1 MNT procedure does not return a list of security flavors,
so our client makes up a list containing just AUTH_NULL. This should
enable nfs_verify_authflavors() to assign the sec= specified flavor,
but instead, it incorrectly sets it to AUTH_NULL.
I expect this would also be a problem for any NFSv3 server whose
MNTv3 MNT procedure returned a security flavor list containing only
AUTH_NULL.
Fixes: e68fd7c8071d ("mount: use sec= that was specified on ... ")
BugLink: https://bugzilla.linux-nfs.org/show_bug.cgi?id=310
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
fs/nfs/super.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
Changes since v1:
- Description edited for accuracy
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index d828ef8..6b179af 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -1691,8 +1691,8 @@ static int nfs_verify_authflavors(struct nfs_parsed_mount_data *args,
rpc_authflavor_t *server_authlist, unsigned int count)
{
rpc_authflavor_t flavor = RPC_AUTH_MAXFLAVOR;
+ bool found_auth_null = false;
unsigned int i;
- int use_auth_null = false;
/*
* If the sec= mount option is used, the specified flavor or AUTH_NULL
@@ -1701,6 +1701,10 @@ static int nfs_verify_authflavors(struct nfs_parsed_mount_data *args,
* AUTH_NULL has a special meaning when it's in the server list - it
* means that the server will ignore the rpc creds, so any flavor
* can be used but still use the sec= that was specified.
+ *
+ * Note also that the MNT procedure in MNTv1 does not return a list
+ * of supported security flavors. In this case, nfs_mount() fabricates
+ * a security flavor list containing just AUTH_NULL.
*/
for (i = 0; i < count; i++) {
flavor = server_authlist[i];
@@ -1709,11 +1713,11 @@ static int nfs_verify_authflavors(struct nfs_parsed_mount_data *args,
goto out;
if (flavor == RPC_AUTH_NULL)
- use_auth_null = true;
+ found_auth_null = true;
}
- if (use_auth_null) {
- flavor = RPC_AUTH_NULL;
+ if (found_auth_null) {
+ flavor = args->auth_info.flavors[0];
goto out;
}
--
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