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author | 2017-04-18 15:31:09 +0100 | |
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committer | 2017-04-18 15:31:49 +0100 | |
commit | c9f838d104fed6f2f61d68164712e3204bf5271b (patch) | |
tree | 11f3973c37a4070994d1f64ed444a233ef7f10b4 | |
parent | KEYS: Change the name of the dead type to ".dead" to prevent user access (diff) | |
download | linux-dev-c9f838d104fed6f2f61d68164712e3204bf5271b.tar.xz linux-dev-c9f838d104fed6f2f61d68164712e3204bf5271b.zip |
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: d84f4f992cbd ("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>
Diffstat (limited to '')
-rw-r--r-- | security/keys/keyctl.c | 11 | ||||
-rw-r--r-- | security/keys/process_keys.c | 44 |
2 files changed, 31 insertions, 24 deletions
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index ab082a2e8fdd..4ad3212adebe 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -1258,8 +1258,8 @@ error: * Read or set the default keyring in which request_key() will cache keys and * return the old setting. * - * If a process keyring is specified then this will be created if it doesn't - * yet exist. The old setting will be returned if successful. + * If a thread or process keyring is specified then it will be created if it + * doesn't yet exist. The old setting will be returned if successful. */ 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: ret = install_process_keyring_to_cred(new); - if (ret < 0) { - if (ret != -EEXIST) - goto error; - ret = 0; - } + if (ret < 0) + goto error; goto set; case KEY_REQKEY_DEFL_DEFAULT: diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c index b6fdd22205b1..9139b18fc863 100644 --- a/security/keys/process_keys.c +++ b/security/keys/process_keys.c @@ -128,13 +128,18 @@ error: } /* - * Install a fresh thread keyring directly to new credentials. This keyring is - * allowed to overrun the quota. + * Install a thread keyring to the given credentials struct if it didn't have + * 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) { struct key *keyring; + if (new->thread_keyring) + return 0; + keyring = keyring_alloc("_tid", new->uid, new->gid, new, KEY_POS_ALL | KEY_USR_VIEW, KEY_ALLOC_QUOTA_OVERRUN, @@ -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) { @@ -158,8 +165,6 @@ static int install_thread_keyring(void) if (!new) return -ENOMEM; - BUG_ON(new->thread_keyring); - ret = install_thread_keyring_to_cred(new); if (ret < 0) { abort_creds(new); @@ -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, - * and other value on any other error + * Return: 0 if a process keyring is now present; -errno on failure. */ int install_process_keyring_to_cred(struct cred *new) { struct key *keyring; if (new->process_keyring) - return -EEXIST; + return 0; keyring = keyring_alloc("_pid", new->uid, new->gid, new, KEY_POS_ALL | KEY_USR_VIEW, @@ -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 - * existing process keyring is not replaced. + * Install a process keyring to the current task if it didn't have one already. * - * Returns 0 if there is a process keyring by the end of this function, some - * error otherwise. + * Return: 0 if a process keyring is now present; -errno on failure. */ static int install_process_keyring(void) { @@ -212,14 +215,18 @@ static int install_process_keyring(void) ret = install_process_keyring_to_cred(new); if (ret < 0) { abort_creds(new); - return ret != -EEXIST ? ret : 0; + return ret; } 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) { @@ -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 - * supplied, an empty one is invented. + * Install the given keyring as the session keyring of the current task, + * 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) { |