[PATCH] KEYS: DH: validate __spare field

[PATCH] KEYS: DH: validate __spare field

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

Syscalls must validate that their reserved arguments are zero and return
EINVAL otherwise.  Otherwise, it will be impossible to actually use them
for anything in the future because existing programs may be passing
garbage in.  This is standard practice when adding new APIs.

Cc: stable@vger.kernel.org # v4.12+
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 security/keys/compat_dh.c | 2 ++
 security/keys/dh.c        | 5 +++++
 2 files changed, 7 insertions(+)

diff --git a/security/keys/compat_dh.c b/security/keys/compat_dh.c
index a6a659b6bcb6..aa6b34cafe5f 100644
--- a/security/keys/compat_dh.c
+++ b/security/keys/compat_dh.c
@@ -33,6 +33,8 @@ long compat_keyctl_dh_compute(struct keyctl_dh_params __user *params,
 	kdfcopy.hashname = compat_ptr(compat_kdfcopy.hashname);
 	kdfcopy.otherinfo = compat_ptr(compat_kdfcopy.otherinfo);
 	kdfcopy.otherinfolen = compat_kdfcopy.otherinfolen;
+	memcpy(kdfcopy.__spare, compat_kdfcopy.__spare,
+	       sizeof(kdfcopy.__spare));
 
 	return __keyctl_dh_compute(params, buffer, buflen, &kdfcopy);
 }
diff --git a/security/keys/dh.c b/security/keys/dh.c
index 4755d4b4f945..d1ea9f325f94 100644
--- a/security/keys/dh.c
+++ b/security/keys/dh.c
@@ -266,6 +266,11 @@ long __keyctl_dh_compute(struct keyctl_dh_params __user *params,
 	if (kdfcopy) {
 		char *hashname;
 
+		if (memchr_inv(kdfcopy->__spare, 0, sizeof(kdfcopy->__spare))) {
+			ret = -EINVAL;
+			goto out1;
+		}
+
 		if (buflen > KEYCTL_KDF_MAX_OUTPUT_LEN ||
 		    kdfcopy->otherinfolen > KEYCTL_KDF_MAX_OI_LEN) {
 			ret = -EMSGSIZE;
-- 
2.13.2

Re: [PATCH] KEYS: DH: validate __spare field

[David Howells]

Eric Biggers <ebiggers3@gmail.com> wrote:

> Syscalls must validate that their reserved arguments are zero and return
> EINVAL otherwise.  Otherwise, it will be impossible to actually use them
> for anything in the future because existing programs may be passing
> garbage in.  This is standard practice when adding new APIs.

Fine by me.  Mat?

David

Re: [PATCH] KEYS: DH: validate __spare field

[Mat Martineau]

On Fri, 7 Jul 2017, David Howells wrote:

> Eric Biggers <ebiggers3@gmail.com> wrote:
>
>> Syscalls must validate that their reserved arguments are zero and return
>> EINVAL otherwise.  Otherwise, it will be impossible to actually use them
>> for anything in the future because existing programs may be passing
>> garbage in.  This is standard practice when adding new APIs.
>
> Fine by me.  Mat?

Looks good, please apply the patch. Thanks for catching this, Eric.

--
Mat Martineau
Intel OTC