Patchwork [4.9,026/119] KEYS: fix dereferencing NULL payload with nonzero length

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Submitter gregkh@linuxfoundation.org
Date June 12, 2017, 3:24 p.m.
Message ID <20170612152558.302305133@linuxfoundation.org>
Download mbox | patch
Permalink /patch/9781573/
State New
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Comments

gregkh@linuxfoundation.org - June 12, 2017, 3:24 p.m.
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Biggers <ebiggers@google.com>

commit 5649645d725c73df4302428ee4e02c869248b4c5 upstream.

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.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 security/keys/keyctl.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Patch

--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -97,7 +97,7 @@  SYSCALL_DEFINE5(add_key, const char __us
 	/* pull the payload in if one was supplied */
 	payload = NULL;
 
-	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)