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KEYS: fix dereferencing NULL payload with nonzero length 

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>
This commit is contained in:
Eric Biggers 2017-06-08 14:48:40 +01:00 committed by James Morris
parent 0f534e4a13
commit 5649645d72
1 changed files with 2 additions and 2 deletions
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4
security/keys/keyctl.c
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@ -99,7 +99,7 @@ SYSCALL_DEFINE5(add_key, const char __user *, _type,
/* pull the payload in if one was supplied */
payload = NULL;
if (_payload) {
if (plen) {
ret = -ENOMEM;
payload = kvmalloc(plen, GFP_KERNEL);
if (!payload)
@ -324,7 +324,7 @@ 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)