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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: d84f4f992c
("CRED: Inaugurate COW credentials")
Cc: stable@vger.kernel.org # 2.6.29+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
parent
c1644fe041
commit
c9f838d104
@ -1258,8 +1258,8 @@ error:
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* Read or set the default keyring in which request_key() will cache keys and
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* return the old setting.
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*
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* If a process keyring is specified then this will be created if it doesn't
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* yet exist. The old setting will be returned if successful.
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* If a thread or process keyring is specified then it will be created if it
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* doesn't yet exist. The old setting will be returned if successful.
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*/
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long keyctl_set_reqkey_keyring(int reqkey_defl)
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{
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@ -1284,11 +1284,8 @@ long keyctl_set_reqkey_keyring(int reqkey_defl)
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case KEY_REQKEY_DEFL_PROCESS_KEYRING:
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ret = install_process_keyring_to_cred(new);
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if (ret < 0) {
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if (ret != -EEXIST)
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goto error;
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ret = 0;
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}
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if (ret < 0)
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goto error;
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goto set;
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case KEY_REQKEY_DEFL_DEFAULT:
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@ -128,13 +128,18 @@ error:
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}
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/*
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* Install a fresh thread keyring directly to new credentials. This keyring is
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* allowed to overrun the quota.
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* Install a thread keyring to the given credentials struct if it didn't have
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* one already. This is allowed to overrun the quota.
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*
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* Return: 0 if a thread keyring is now present; -errno on failure.
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*/
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int install_thread_keyring_to_cred(struct cred *new)
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{
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struct key *keyring;
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if (new->thread_keyring)
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return 0;
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keyring = keyring_alloc("_tid", new->uid, new->gid, new,
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KEY_POS_ALL | KEY_USR_VIEW,
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KEY_ALLOC_QUOTA_OVERRUN,
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@ -147,7 +152,9 @@ int install_thread_keyring_to_cred(struct cred *new)
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}
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/*
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* Install a fresh thread keyring, discarding the old one.
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* Install a thread keyring to the current task if it didn't have one already.
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*
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* Return: 0 if a thread keyring is now present; -errno on failure.
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*/
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static int install_thread_keyring(void)
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{
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@ -158,8 +165,6 @@ static int install_thread_keyring(void)
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if (!new)
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return -ENOMEM;
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BUG_ON(new->thread_keyring);
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ret = install_thread_keyring_to_cred(new);
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if (ret < 0) {
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abort_creds(new);
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@ -170,17 +175,17 @@ static int install_thread_keyring(void)
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}
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/*
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* Install a process keyring directly to a credentials struct.
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* Install a process keyring to the given credentials struct if it didn't have
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* one already. This is allowed to overrun the quota.
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*
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* Returns -EEXIST if there was already a process keyring, 0 if one installed,
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* and other value on any other error
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* Return: 0 if a process keyring is now present; -errno on failure.
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*/
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int install_process_keyring_to_cred(struct cred *new)
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{
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struct key *keyring;
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if (new->process_keyring)
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return -EEXIST;
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return 0;
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keyring = keyring_alloc("_pid", new->uid, new->gid, new,
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KEY_POS_ALL | KEY_USR_VIEW,
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@ -194,11 +199,9 @@ int install_process_keyring_to_cred(struct cred *new)
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}
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/*
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* Make sure a process keyring is installed for the current process. The
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* existing process keyring is not replaced.
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* Install a process keyring to the current task if it didn't have one already.
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*
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* Returns 0 if there is a process keyring by the end of this function, some
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* error otherwise.
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* Return: 0 if a process keyring is now present; -errno on failure.
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*/
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static int install_process_keyring(void)
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{
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@ -212,14 +215,18 @@ static int install_process_keyring(void)
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ret = install_process_keyring_to_cred(new);
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if (ret < 0) {
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abort_creds(new);
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return ret != -EEXIST ? ret : 0;
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return ret;
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}
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return commit_creds(new);
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}
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/*
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* Install a session keyring directly to a credentials struct.
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* Install the given keyring as the session keyring of the given credentials
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* struct, replacing the existing one if any. If the given keyring is NULL,
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* then install a new anonymous session keyring.
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*
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* Return: 0 on success; -errno on failure.
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*/
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int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
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{
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@ -254,8 +261,11 @@ int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
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}
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/*
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* Install a session keyring, discarding the old one. If a keyring is not
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* supplied, an empty one is invented.
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* Install the given keyring as the session keyring of the current task,
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* replacing the existing one if any. If the given keyring is NULL, then
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* install a new anonymous session keyring.
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*
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* Return: 0 on success; -errno on failure.
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*/
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static int install_session_keyring(struct key *keyring)
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{
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