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KEYS: fix dereferencing NULL payload with nonzero length 

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.

Change-Id: I1f7328e3f7677cee5b3e5ba3969b5f0f9a9d4927
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>
This commit is contained in:
Eric Biggers 2017-06-08 14:48:40 +01:00 committed by LuK1337
parent f27273f9e1
commit 74149aa05f
1 changed files with 2 additions and 2 deletions
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4
security/keys/keyctl.c
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@ -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)