[SRU,Trusty,1/1] KEYS: fix dereferencing NULL payload with nonzero length

Message ID 20171207175957.9630-2-kleber.souza@canonical.com
State New
Headers show
  • Fix for CVE-2017-15274
Related show

Commit Message

Kleber Souza Dec. 7, 2017, 5:59 p.m.
From: Eric Biggers <ebiggers@google.com>

sys_add_key() and the KEYCTL_UPDATE operation of sys_keyctl() allowed a
NULL payload with nonzero length to be passed to the key type's
->preparse(), ->instantiate(), and/or ->update() methods.  Various key
types including asymmetric, cifs.idmap, cifs.spnego, and pkcs7_test did
not handle this case, allowing an unprivileged user to trivially cause a
NULL pointer dereference (kernel oops) if one of these key types was
present.  Fix it by doing the copy_from_user() when 'plen' is nonzero
rather than when '_payload' is non-NULL, causing the syscall to fail
with EFAULT as expected when an invalid buffer is specified.

Cc: stable@vger.kernel.org # 2.6.10+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>

(backported from commit 5649645d725c73df4302428ee4e02c869248b4c5)
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
 security/keys/keyctl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)


diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 4e3fecc72f43..e4bb9adf7a76 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -93,7 +93,7 @@  SYSCALL_DEFINE5(add_key, const char __user *, _type,
 	payload = NULL;
 	vm = false;
-	if (_payload) {
+	if (plen) {
 		ret = -ENOMEM;
 		payload = kmalloc(plen, GFP_KERNEL | __GFP_NOWARN);
 		if (!payload) {
@@ -327,7 +327,7 @@  long keyctl_update_key(key_serial_t id,
 	/* pull the payload in if one was supplied */
 	payload = NULL;
-	if (_payload) {
+	if (plen) {
 		ret = -ENOMEM;
 		payload = kmalloc(plen, GFP_KERNEL);
 		if (!payload)