From e59428f721ee096d8a020504ea908a6f0d952735 Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 19 Jun 2019 16:10:15 +0100 Subject: keys: Move the RCU locks outwards from the keyring search functions Move the RCU locks outwards from the keyring search functions so that it will become possible to provide an RCU-capable partial request_key() function in a later commit. Signed-off-by: David Howells --- include/keys/request_key_auth-type.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/keys/request_key_auth-type.h b/include/keys/request_key_auth-type.h index a726dd3f1dc6..2a046062bb42 100644 --- a/include/keys/request_key_auth-type.h +++ b/include/keys/request_key_auth-type.h @@ -18,6 +18,7 @@ * Authorisation record for request_key(). */ struct request_key_auth { + struct rcu_head rcu; struct key *target_key; struct key *dest_keyring; const struct cred *cred; -- cgit v1.2.3 From 896f1950e5944532b971d880a6bae7fba3b6a8d3 Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 19 Jun 2019 16:10:15 +0100 Subject: keys: Provide request_key_rcu() Provide a request_key_rcu() function that can be used to request a key under RCU conditions. It can only search and check permissions; it cannot allocate a new key, upcall or wait for an upcall to complete. It may return a partially constructed key. Signed-off-by: David Howells --- include/linux/key.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include') diff --git a/include/linux/key.h b/include/linux/key.h index 612e1cf84049..3604a554df99 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -274,6 +274,9 @@ extern struct key *request_key(struct key_type *type, const char *description, const char *callout_info); +extern struct key *request_key_rcu(struct key_type *type, + const char *description); + extern struct key *request_key_with_auxdata(struct key_type *type, const char *description, const void *callout_info, -- cgit v1.2.3 From 7743c48e54ee9be9c799cbf3b8e3e9f2b8d19e72 Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 19 Jun 2019 16:10:15 +0100 Subject: keys: Cache result of request_key*() temporarily in task_struct If a filesystem uses keys to hold authentication tokens, then it needs a token for each VFS operation that might perform an authentication check - either by passing it to the server, or using to perform a check based on authentication data cached locally. For open files this isn't a problem, since the key should be cached in the file struct since it represents the subject performing operations on that file descriptor. During pathwalk, however, there isn't anywhere to cache the key, except perhaps in the nameidata struct - but that isn't exposed to the filesystems. Further, a pathwalk can incur a lot of operations, calling one or more of the following, for instance: ->lookup() ->permission() ->d_revalidate() ->d_automount() ->get_acl() ->getxattr() on each dentry/inode it encounters - and each one may need to call request_key(). And then, at the end of pathwalk, it will call the actual operation: ->mkdir() ->mknod() ->getattr() ->open() ... which may need to go and get the token again. However, it is very likely that all of the operations on a single dentry/inode - and quite possibly a sequence of them - will all want to use the same authentication token, which suggests that caching it would be a good idea. To this end: (1) Make it so that a positive result of request_key() and co. that didn't require upcalling to userspace is cached temporarily in task_struct. (2) The cache is 1 deep, so a new result displaces the old one. (3) The key is released by exit and by notify-resume. (4) The cache is cleared in a newly forked process. Signed-off-by: David Howells --- include/linux/sched.h | 5 +++++ include/linux/tracehook.h | 7 +++++++ 2 files changed, 12 insertions(+) (limited to 'include') diff --git a/include/linux/sched.h b/include/linux/sched.h index 11837410690f..e5f18857dd53 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -831,6 +831,11 @@ struct task_struct { /* Effective (overridable) subjective task credentials (COW): */ const struct cred __rcu *cred; +#ifdef CONFIG_KEYS + /* Cached requested key. */ + struct key *cached_requested_key; +#endif + /* * executable name, excluding path. * diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h index df20f8bdbfa3..81824467e6a6 100644 --- a/include/linux/tracehook.h +++ b/include/linux/tracehook.h @@ -187,6 +187,13 @@ static inline void tracehook_notify_resume(struct pt_regs *regs) if (unlikely(current->task_works)) task_work_run(); +#ifdef CONFIG_KEYS_REQUEST_CACHE + if (unlikely(current->cached_requested_key)) { + key_put(current->cached_requested_key); + current->cached_requested_key = NULL; + } +#endif + mem_cgroup_handle_over_high(); blkcg_maybe_throttle_current(); } -- cgit v1.2.3 From 3b8c4a08a471d56ecaaca939c972fdf5b8255629 Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 19 Jun 2019 16:10:16 +0100 Subject: keys: Kill off request_key_async{,_with_auxdata} Kill off request_key_async{,_with_auxdata}() as they're not currently used. Signed-off-by: David Howells --- include/linux/key.h | 11 ----------- 1 file changed, 11 deletions(-) (limited to 'include') diff --git a/include/linux/key.h b/include/linux/key.h index 3604a554df99..4cd5669184f3 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -283,17 +283,6 @@ extern struct key *request_key_with_auxdata(struct key_type *type, size_t callout_len, void *aux); -extern struct key *request_key_async(struct key_type *type, - const char *description, - const void *callout_info, - size_t callout_len); - -extern struct key *request_key_async_with_auxdata(struct key_type *type, - const char *description, - const void *callout_info, - size_t callout_len, - void *aux); - extern int wait_for_key_construction(struct key *key, bool intr); extern int key_validate(const struct key *key); -- cgit v1.2.3