Commit c9f838d1 authored by Eric Biggers's avatar Eric Biggers Committed by David Howells

KEYS: fix keyctl_set_reqkey_keyring() to not leak thread keyrings

This fixes CVE-2017-7472.

Running the following program as an unprivileged user exhausts kernel
memory by leaking thread keyrings:

	#include <keyutils.h>

	int main()
	{
		for (;;)
			keyctl_set_reqkey_keyring(KEY_REQKEY_DEFL_THREAD_KEYRING);
	}

Fix it by only creating a new thread keyring if there wasn't one before.
To make things more consistent, make install_thread_keyring_to_cred()
and install_process_keyring_to_cred() both return 0 if the corresponding
keyring is already present.

Fixes: d84f4f99 ("CRED: Inaugurate COW credentials")
Cc: stable@vger.kernel.org # 2.6.29+
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
parent c1644fe0
...@@ -1258,8 +1258,8 @@ long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error, ...@@ -1258,8 +1258,8 @@ long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error,
* Read or set the default keyring in which request_key() will cache keys and * Read or set the default keyring in which request_key() will cache keys and
* return the old setting. * return the old setting.
* *
* If a process keyring is specified then this will be created if it doesn't * If a thread or process keyring is specified then it will be created if it
* yet exist. The old setting will be returned if successful. * doesn't yet exist. The old setting will be returned if successful.
*/ */
long keyctl_set_reqkey_keyring(int reqkey_defl) long keyctl_set_reqkey_keyring(int reqkey_defl)
{ {
...@@ -1284,11 +1284,8 @@ long keyctl_set_reqkey_keyring(int reqkey_defl) ...@@ -1284,11 +1284,8 @@ long keyctl_set_reqkey_keyring(int reqkey_defl)
case KEY_REQKEY_DEFL_PROCESS_KEYRING: case KEY_REQKEY_DEFL_PROCESS_KEYRING:
ret = install_process_keyring_to_cred(new); ret = install_process_keyring_to_cred(new);
if (ret < 0) { if (ret < 0)
if (ret != -EEXIST) goto error;
goto error;
ret = 0;
}
goto set; goto set;
case KEY_REQKEY_DEFL_DEFAULT: case KEY_REQKEY_DEFL_DEFAULT:
......
...@@ -128,13 +128,18 @@ int install_user_keyrings(void) ...@@ -128,13 +128,18 @@ int install_user_keyrings(void)
} }
/* /*
* Install a fresh thread keyring directly to new credentials. This keyring is * Install a thread keyring to the given credentials struct if it didn't have
* allowed to overrun the quota. * one already. This is allowed to overrun the quota.
*
* Return: 0 if a thread keyring is now present; -errno on failure.
*/ */
int install_thread_keyring_to_cred(struct cred *new) int install_thread_keyring_to_cred(struct cred *new)
{ {
struct key *keyring; struct key *keyring;
if (new->thread_keyring)
return 0;
keyring = keyring_alloc("_tid", new->uid, new->gid, new, keyring = keyring_alloc("_tid", new->uid, new->gid, new,
KEY_POS_ALL | KEY_USR_VIEW, KEY_POS_ALL | KEY_USR_VIEW,
KEY_ALLOC_QUOTA_OVERRUN, KEY_ALLOC_QUOTA_OVERRUN,
...@@ -147,7 +152,9 @@ int install_thread_keyring_to_cred(struct cred *new) ...@@ -147,7 +152,9 @@ int install_thread_keyring_to_cred(struct cred *new)
} }
/* /*
* Install a fresh thread keyring, discarding the old one. * Install a thread keyring to the current task if it didn't have one already.
*
* Return: 0 if a thread keyring is now present; -errno on failure.
*/ */
static int install_thread_keyring(void) static int install_thread_keyring(void)
{ {
...@@ -158,8 +165,6 @@ static int install_thread_keyring(void) ...@@ -158,8 +165,6 @@ static int install_thread_keyring(void)
if (!new) if (!new)
return -ENOMEM; return -ENOMEM;
BUG_ON(new->thread_keyring);
ret = install_thread_keyring_to_cred(new); ret = install_thread_keyring_to_cred(new);
if (ret < 0) { if (ret < 0) {
abort_creds(new); abort_creds(new);
...@@ -170,17 +175,17 @@ static int install_thread_keyring(void) ...@@ -170,17 +175,17 @@ static int install_thread_keyring(void)
} }
/* /*
* Install a process keyring directly to a credentials struct. * Install a process keyring to the given credentials struct if it didn't have
* one already. This is allowed to overrun the quota.
* *
* Returns -EEXIST if there was already a process keyring, 0 if one installed, * Return: 0 if a process keyring is now present; -errno on failure.
* and other value on any other error
*/ */
int install_process_keyring_to_cred(struct cred *new) int install_process_keyring_to_cred(struct cred *new)
{ {
struct key *keyring; struct key *keyring;
if (new->process_keyring) if (new->process_keyring)
return -EEXIST; return 0;
keyring = keyring_alloc("_pid", new->uid, new->gid, new, keyring = keyring_alloc("_pid", new->uid, new->gid, new,
KEY_POS_ALL | KEY_USR_VIEW, KEY_POS_ALL | KEY_USR_VIEW,
...@@ -194,11 +199,9 @@ int install_process_keyring_to_cred(struct cred *new) ...@@ -194,11 +199,9 @@ int install_process_keyring_to_cred(struct cred *new)
} }
/* /*
* Make sure a process keyring is installed for the current process. The * Install a process keyring to the current task if it didn't have one already.
* existing process keyring is not replaced.
* *
* Returns 0 if there is a process keyring by the end of this function, some * Return: 0 if a process keyring is now present; -errno on failure.
* error otherwise.
*/ */
static int install_process_keyring(void) static int install_process_keyring(void)
{ {
...@@ -212,14 +215,18 @@ static int install_process_keyring(void) ...@@ -212,14 +215,18 @@ static int install_process_keyring(void)
ret = install_process_keyring_to_cred(new); ret = install_process_keyring_to_cred(new);
if (ret < 0) { if (ret < 0) {
abort_creds(new); abort_creds(new);
return ret != -EEXIST ? ret : 0; return ret;
} }
return commit_creds(new); return commit_creds(new);
} }
/* /*
* Install a session keyring directly to a credentials struct. * Install the given keyring as the session keyring of the given credentials
* struct, replacing the existing one if any. If the given keyring is NULL,
* then install a new anonymous session keyring.
*
* Return: 0 on success; -errno on failure.
*/ */
int install_session_keyring_to_cred(struct cred *cred, struct key *keyring) int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
{ {
...@@ -254,8 +261,11 @@ int install_session_keyring_to_cred(struct cred *cred, struct key *keyring) ...@@ -254,8 +261,11 @@ int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
} }
/* /*
* Install a session keyring, discarding the old one. If a keyring is not * Install the given keyring as the session keyring of the current task,
* supplied, an empty one is invented. * replacing the existing one if any. If the given keyring is NULL, then
* install a new anonymous session keyring.
*
* Return: 0 on success; -errno on failure.
*/ */
static int install_session_keyring(struct key *keyring) static int install_session_keyring(struct key *keyring)
{ {
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment