Commit 400773b3 authored by Eric Biggers's avatar Eric Biggers Committed by Ben Hutchings

KEYS: fix dereferencing NULL payload with nonzero length

commit 5649645d 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: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarJames Morris <james.l.morris@oracle.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
parent 2ae7cdab
......@@ -97,7 +97,7 @@ 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) {
......@@ -331,7 +331,7 @@ 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)
......
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