A while back I had reported that an NFSv3 client could successfully
mount using '-o xprtsec=none' an export that had been exported with
'xprtsec=tls:mtls'. By "successfully" I mean that the mount command
would succeed and the mount would show up in /proc/mount. Attempting to
do anything futher with the mount would be met with NFS3ERR_ACCES.
This was fixed (albeit accidentally) by bb4f07f2409c ("nfsd: Fix
NFSD_MAY_BYPASS_GSS and NFSD_MAY_BYPASS_GSS_ON_ROOT") and was
subsequently re-broken by 0813c5f01249 ("nfsd: fix access checking for
NLM under XPRTSEC policies").
Transport Layer Security isn't an RPC security flavor or pseudo-flavor,
so we shouldn't be conflating them when determining whether the access
checks can be bypassed. Split check_nfsd_access() into two helpers, and
have __fh_verify() call the helpers directly since __fh_verify() has
logic that allows one or both of the checks to be skipped. All other
sites will continue to call check_nfsd_access().
Link: https://lore.kernel.org/linux-nfs/ZjO3Qwf_G87yNXb2@aion/
Fixes: 9280c5774314 ("NFSD: Handle new xprtsec= export option")
Signed-off-by: Scott Mayhew <smayhew@xxxxxxxxxx>
---
fs/nfsd/export.c | 83 +++++++++++++++++++++++++++++++++---------------
fs/nfsd/export.h | 3 ++
fs/nfsd/nfsfh.c | 24 +++++++++++++-
3 files changed, 84 insertions(+), 26 deletions(-)
diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index cadfc2bae60e..1c46864464ff 100644
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -1082,50 +1082,62 @@ static struct svc_export *exp_find(struct cache_detail *cd,
}
/**
- * check_nfsd_access - check if access to export is allowed.
+ * check_xprtsec_policy - check if access to export is allowed by the
+ * xprtsec policy
* @exp: svc_export that is being accessed.
- * @rqstp: svc_rqst attempting to access @exp (will be NULL for LOCALIO).
- * @may_bypass_gss: reduce strictness of authorization check
+ * @rqstp: svc_rqst attempting to access @exp.
+ *
+ * Helper function for check_nfsd_access(). Note that callers should be
+ * using check_nfsd_access() instead of calling this function directly. The
+ * one exception is __fh_verify() since it has logic that may result in one
+ * or both of the helpers being skipped.
*
* Return values:
* %nfs_ok if access is granted, or
* %nfserr_wrongsec if access is denied
*/
-__be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp,
- bool may_bypass_gss)
+__be32 check_xprtsec_policy(struct svc_export *exp, struct svc_rqst *rqstp)
{
- struct exp_flavor_info *f, *end = exp->ex_flavors + exp->ex_nflavors;
- struct svc_xprt *xprt;
-
- /*
- * If rqstp is NULL, this is a LOCALIO request which will only
- * ever use a filehandle/credential pair for which access has
- * been affirmed (by ACCESS or OPEN NFS requests) over the
- * wire. So there is no need for further checks here.
- */
- if (!rqstp)
- return nfs_ok;
-
- xprt = rqstp->rq_xprt;
+ struct svc_xprt *xprt = rqstp->rq_xprt;
if (exp->ex_xprtsec_modes & NFSEXP_XPRTSEC_NONE) {
if (!test_bit(XPT_TLS_SESSION, &xprt->xpt_flags))
- goto ok;
+ return nfs_ok;
}
if (exp->ex_xprtsec_modes & NFSEXP_XPRTSEC_TLS) {
if (test_bit(XPT_TLS_SESSION, &xprt->xpt_flags) &&
!test_bit(XPT_PEER_AUTH, &xprt->xpt_flags))
- goto ok;
+ return nfs_ok;
}
if (exp->ex_xprtsec_modes & NFSEXP_XPRTSEC_MTLS) {
if (test_bit(XPT_TLS_SESSION, &xprt->xpt_flags) &&
test_bit(XPT_PEER_AUTH, &xprt->xpt_flags))
- goto ok;
+ return nfs_ok;
}
- if (!may_bypass_gss)
- goto denied;
+ return nfserr_wrongsec;
+}
+
+/**
+ * check_security flavor - check if access to export is allowed by the
+ * security flavor
+ * @exp: svc_export that is being accessed.
+ * @rqstp: svc_rqst attempting to access @exp.
+ * @may_bypass_gss: reduce strictness of authorization check
+ *
+ * Helper function for check_nfsd_access(). Note that callers should be
+ * using check_nfsd_access() instead of calling this function directly. The
+ * one exception is __fh_verify() since it has logic that may result in one
+ * or both of the helpers being skipped.
+ *
+ * Return values:
+ * %nfs_ok if access is granted, or
+ * %nfserr_wrongsec if access is denied
+ */
+__be32 check_security_flavor(struct svc_export *exp, struct svc_rqst *rqstp,
+ bool may_bypass_gss)
+{
+ struct exp_flavor_info *f, *end = exp->ex_flavors + exp->ex_nflavors;
-ok:
/* legacy gss-only clients are always OK: */
if (exp->ex_client == rqstp->rq_gssclient)
return nfs_ok;
@@ -1167,10 +1179,31 @@ __be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp,
}
}
-denied:
return nfserr_wrongsec;
}
+/**
+ * check_nfsd_access - check if access to export is allowed.
+ * @exp: svc_export that is being accessed.
+ * @rqstp: svc_rqst attempting to access @exp.
+ * @may_bypass_gss: reduce strictness of authorization check
+ *
+ * Return values:
+ * %nfs_ok if access is granted, or
+ * %nfserr_wrongsec if access is denied
+ */
+__be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp,
+ bool may_bypass_gss)
+{
+ __be32 status;
+
+ status = check_xprtsec_policy(exp, rqstp);
+ if (status != nfs_ok)
+ return status;
+
+ return check_security_flavor(exp, rqstp, may_bypass_gss);
+}
+
/*
* Uses rq_client and rq_gssclient to find an export; uses rq_client (an
* auth_unix client) if it's available and has secinfo information;
diff --git a/fs/nfsd/export.h b/fs/nfsd/export.h
index b9c0adb3ce09..ef5581911d5b 100644
--- a/fs/nfsd/export.h
+++ b/fs/nfsd/export.h
@@ -101,6 +101,9 @@ struct svc_expkey {
struct svc_cred;
int nfsexp_flags(struct svc_cred *cred, struct svc_export *exp);
+__be32 check_xprtsec_policy(struct svc_export *exp, struct svc_rqst *rqstp);
+__be32 check_security_flavor(struct svc_export *exp, struct svc_rqst *rqstp,
+ bool may_bypass_gss);
__be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp,
bool may_bypass_gss);
diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index 74cf1f4de174..1078a4c763b0 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -364,10 +364,30 @@ __fh_verify(struct svc_rqst *rqstp,
if (error)
goto out;
+ /*
+ * If rqstp is NULL, this is a LOCALIO request which will only
+ * ever use a filehandle/credential pair for which access has
+ * been affirmed (by ACCESS or OPEN NFS requests) over the
+ * wire. Skip both the xprtsec policy and the security flavor
+ * checks.
+ */
+ if (!rqstp)
+ goto check_permissions;
+
if ((access & NFSD_MAY_NLM) && (exp->ex_flags & NFSEXP_NOAUTHNLM))
/* NLM is allowed to fully bypass authentication */
goto out;
+ /*
+ * NLM is allowed to bypass the xprtsec policy check because lockd
+ * doesn't support xprtsec.
+ */
+ if (!(access & NFSD_MAY_NLM)) {
+ error = check_xprtsec_policy(exp, rqstp);
+ if (error)
+ goto out;
+ }
+
if (access & NFSD_MAY_BYPASS_GSS)
may_bypass_gss = true;
/*
@@ -379,13 +399,15 @@ __fh_verify(struct svc_rqst *rqstp,
&& exp->ex_path.dentry == dentry)
may_bypass_gss = true;
- error = check_nfsd_access(exp, rqstp, may_bypass_gss);
+ error = check_security_flavor(exp, rqstp, may_bypass_gss);
if (error)
goto out;
+
/* During LOCALIO call to fh_verify will be called with a NULL rqstp */
if (rqstp)
svc_xprt_set_valid(rqstp->rq_xprt);
+check_permissions:
/* Finally, check access permissions. */
error = nfsd_permission(cred, exp, dentry, access);
out:
--
2.48.1
