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Subject[PATCH v2 -mm 1/2] umh && creds: convert call_usermodehelper_keys() to use subprocess_info->init()
call_usermodehelper_keys() uses call_usermodehelper_setkeys() to change
subprocess_info->cred in advance. Now that we have info->init() we can
change this code to set tgcred->session_keyring in context of execing
kernel thread.

Note: since currently call_usermodehelper_keys() is never called with
UMH_NO_WAIT, call_usermodehelper_keys()->key_get() and umh_keys_cleanup()
are not really needed, we could rely on install_session_keyring_to_cred()
which does key_get() on success.

Compile tested.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
include/linux/kmod.h | 17 -----------------
kernel/kmod.c | 18 ------------------
security/keys/internal.h | 1 +
security/keys/process_keys.c | 3 +--
security/keys/request_key.c | 33 +++++++++++++++++++++++++++++++++
5 files changed, 35 insertions(+), 37 deletions(-)
--- mm/include/linux/kmod.h~1_CONVERT_KEYS 2010-02-25 17:37:41.000000000 +0100
+++ mm/include/linux/kmod.h 2010-02-26 20:18:48.000000000 +0100
@@ -71,8 +71,6 @@ struct subprocess_info *call_usermodehel
char **envp, gfp_t gfp_mask);

/* Set various pieces of state into the subprocess_info structure */
-void call_usermodehelper_setkeys(struct subprocess_info *info,
- struct key *session_keyring);
void call_usermodehelper_setfns(struct subprocess_info *info,
int (*init)(struct subprocess_info *info),
void (*cleanup)(struct subprocess_info *info),
@@ -108,21 +106,6 @@ call_usermodehelper(char *path, char **a
wait, NULL, NULL, NULL);
}

-static inline int
-call_usermodehelper_keys(char *path, char **argv, char **envp,
- struct key *session_keyring, enum umh_wait wait)
-{
- struct subprocess_info *info;
- gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
-
- info = call_usermodehelper_setup(path, argv, envp, gfp_mask);
- if (info == NULL)
- return -ENOMEM;
-
- call_usermodehelper_setkeys(info, session_keyring);
- return call_usermodehelper_exec(info, wait);
-}
-
extern void usermodehelper_init(void);

extern int usermodehelper_disable(void);
--- mm/kernel/kmod.c~1_CONVERT_KEYS 2010-02-25 17:37:41.000000000 +0100
+++ mm/kernel/kmod.c 2010-02-26 20:18:48.000000000 +0100
@@ -386,24 +386,6 @@ struct subprocess_info *call_usermodehel
EXPORT_SYMBOL(call_usermodehelper_setup);

/**
- * call_usermodehelper_setkeys - set the session keys for usermode helper
- * @info: a subprocess_info returned by call_usermodehelper_setup
- * @session_keyring: the session keyring for the process
- */
-void call_usermodehelper_setkeys(struct subprocess_info *info,
- struct key *session_keyring)
-{
-#ifdef CONFIG_KEYS
- struct thread_group_cred *tgcred = info->cred->tgcred;
- key_put(tgcred->session_keyring);
- tgcred->session_keyring = key_get(session_keyring);
-#else
- BUG();
-#endif
-}
-EXPORT_SYMBOL(call_usermodehelper_setkeys);
-
-/**
* call_usermodehelper_setfns - set a cleanup/init function
* @info: a subprocess_info returned by call_usermodehelper_setup
* @cleanup: a cleanup function
--- mm/security/keys/internal.h~1_CONVERT_KEYS 2010-02-25 15:22:14.000000000 +0100
+++ mm/security/keys/internal.h 2010-02-26 20:30:52.000000000 +0100
@@ -115,6 +115,7 @@ extern struct key *find_keyring_by_name(
extern int install_user_keyrings(void);
extern int install_thread_keyring_to_cred(struct cred *);
extern int install_process_keyring_to_cred(struct cred *);
+extern int install_session_keyring_to_cred(struct cred *, struct key *);

extern struct key *request_key_and_link(struct key_type *type,
const char *description,
--- mm/security/keys/process_keys.c~1_CONVERT_KEYS 2010-02-25 15:22:14.000000000 +0100
+++ mm/security/keys/process_keys.c 2010-02-26 20:22:14.000000000 +0100
@@ -217,8 +217,7 @@ static int install_process_keyring(void)
/*
* install a session keyring directly to a credentials struct
*/
-static int install_session_keyring_to_cred(struct cred *cred,
- struct key *keyring)
+int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
{
unsigned long flags;
struct key *old;
--- mm/security/keys/request_key.c~1_CONVERT_KEYS 2010-02-25 17:37:41.000000000 +0100
+++ mm/security/keys/request_key.c 2010-02-26 20:42:56.000000000 +0100
@@ -58,6 +58,39 @@ void complete_request_key(struct key_con
}
EXPORT_SYMBOL(complete_request_key);

+static int umh_keys_init(struct subprocess_info *info)
+{
+ struct cred *cred = (struct cred*)current_cred();
+ struct key *keyring = info->data;
+ /*
+ * This is called in context of freshly forked kthread before
+ * kernel_execve(), we can just change our ->session_keyring.
+ */
+ return install_session_keyring_to_cred(cred, keyring);
+}
+
+static void umh_keys_cleanup(struct subprocess_info *info)
+{
+ struct key *keyring = info->data;
+ key_put(keyring);
+}
+
+static inline int
+call_usermodehelper_keys(char *path, char **argv, char **envp,
+ struct key *session_keyring, enum umh_wait wait)
+{
+ gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
+ struct subprocess_info *info =
+ call_usermodehelper_setup(path, argv, envp, gfp_mask);
+
+ if (!info)
+ return -ENOMEM;
+
+ call_usermodehelper_setfns(info, umh_keys_init, umh_keys_cleanup,
+ key_get(session_keyring));
+ return call_usermodehelper_exec(info, wait);
+}
+
/*
* request userspace finish the construction of a key
* - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"


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