nfsd: Sanity check the ACL attribute

When an ACL is presented to the NFSv4 server in
Setattr or Verify, parsing of the ACL assumed a
sane acecnt and sane sizes for the "who" strings.
This patch adds sanity checks for these.

The patch also fixes handling of an error
return from nfsrv_dissectacl() for one broken
case.

Reported by:	rtm@lcs.mit.edu
Tested by:	rtm@lcs.mit.edu
PR:	260111
MFC after:	2 weeks

2 files changed, 15 insertions, 1 deletions

diff --git a/sys/fs/nfs/nfs_commonacl.c b/sys/fs/nfs/nfs_commonacl.c
index 99a67edc044d..19492675e731 100644
--- a/sys/fs/nfs/nfs_commonacl.c
+++ b/sys/fs/nfs/nfs_commonacl.c
@@ -58,7 +58,11 @@ nfsrv_dissectace(struct nfsrv_descript *nd, struct acl_entry *acep,
 	flag = fxdr_unsigned(u_int32_t, *tl++);
 	mask = fxdr_unsigned(u_int32_t, *tl++);
 	len = fxdr_unsigned(int, *tl);
-	if (len < 0) {
+	/*
+	 * The RFCs do not specify a limit to the length of the "who", but
+	 * NFSV4_OPAQUELIMIT (1024) should be sufficient.
+	 */
+	if (len < 0 || len > NFSV4_OPAQUELIMIT) {
 		error = NFSERR_BADXDR;
 		goto nfsmout;
 	} else if (len == 0) {
diff --git a/sys/fs/nfs/nfs_commonsubs.c b/sys/fs/nfs/nfs_commonsubs.c
index 910f10eb1b4a..d882d248ef7f 100644
--- a/sys/fs/nfs/nfs_commonsubs.c
+++ b/sys/fs/nfs/nfs_commonsubs.c
@@ -1107,6 +1107,14 @@ nfsrv_dissectacl(struct nfsrv_descript *nd, NFSACL_T *aclp, int *aclerrp,
 	NFSM_DISSECT(tl, u_int32_t *, NFSX_UNSIGNED);
 	aclsize = NFSX_UNSIGNED;
 	acecnt = fxdr_unsigned(int, *tl);
+	/*
+	 * The RFCs do not define a fixed limit to the number of ACEs in
+	 * an ACL, but 10240 should be more than sufficient.
+	 */
+	if (acecnt < 0 || acecnt > 10240) {
+		error = NFSERR_BADXDR;
+		goto nfsmout;
+	}
 	if (acecnt > ACL_MAX_ENTRIES)
 		aceerr = NFSERR_ATTRNOTSUPP;
 	if (nfsrv_useacl == 0)
@@ -1492,6 +1500,8 @@ nfsv4_loadattr(struct nfsrv_descript *nd, vnode_t vp,
 			    } else {
 				error = nfsrv_dissectacl(nd, NULL, &aceerr,
 				    &cnt, p);
+				if (error)
+				    goto nfsmout;
 				*retcmpp = NFSERR_ATTRNOTSUPP;
 			    }
 			  }