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Subject[PATCH v2 -mm 2/2] umh && creds: kill subprocess_info->cred logic
Now that nobody ever changes subprocess_info->cred we can kill this
member and related code. ____call_usermodehelper() always runs in the
context of freshly forked kernel thread, it has the proper ->cred
copied from its parent kthread, keventd.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
include/linux/cred.h | 1
include/linux/kmod.h | 1
kernel/cred.c | 54 ---------------------------------------------------
kernel/kmod.c | 19 -----------------
4 files changed, 75 deletions(-)
--- mm/include/linux/cred.h~2_KILL_INFO_CRED 2010-02-26 20:18:48.000000000 +0100
+++ mm/include/linux/cred.h 2010-02-26 20:53:04.000000000 +0100
@@ -156,7 +156,6 @@ extern int copy_creds(struct task_struct
extern struct cred *cred_alloc_blank(void);
extern struct cred *prepare_creds(void);
extern struct cred *prepare_exec_creds(void);
-extern struct cred *prepare_usermodehelper_creds(void);
extern int commit_creds(struct cred *);
extern void abort_creds(struct cred *);
extern const struct cred *override_creds(const struct cred *);
--- mm/include/linux/kmod.h~2_KILL_INFO_CRED 2010-02-26 20:18:48.000000000 +0100
+++ mm/include/linux/kmod.h 2010-02-26 20:53:04.000000000 +0100
@@ -55,7 +55,6 @@ enum umh_wait {
struct subprocess_info {
struct work_struct work;
struct completion *complete;
- struct cred *cred;
char *path;
char **argv;
char **envp;
--- mm/kernel/cred.c~2_KILL_INFO_CRED 2010-02-26 20:18:48.000000000 +0100
+++ mm/kernel/cred.c 2010-02-26 20:53:04.000000000 +0100
@@ -347,60 +347,6 @@ struct cred *prepare_exec_creds(void)
}

/*
- * prepare new credentials for the usermode helper dispatcher
- */
-struct cred *prepare_usermodehelper_creds(void)
-{
-#ifdef CONFIG_KEYS
- struct thread_group_cred *tgcred = NULL;
-#endif
- struct cred *new;
-
-#ifdef CONFIG_KEYS
- tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC);
- if (!tgcred)
- return NULL;
-#endif
-
- new = kmem_cache_alloc(cred_jar, GFP_ATOMIC);
- if (!new)
- return NULL;
-
- kdebug("prepare_usermodehelper_creds() alloc %p", new);
-
- memcpy(new, &init_cred, sizeof(struct cred));
-
- atomic_set(&new->usage, 1);
- set_cred_subscribers(new, 0);
- get_group_info(new->group_info);
- get_uid(new->user);
-
-#ifdef CONFIG_KEYS
- new->thread_keyring = NULL;
- new->request_key_auth = NULL;
- new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT;
-
- atomic_set(&tgcred->usage, 1);
- spin_lock_init(&tgcred->lock);
- new->tgcred = tgcred;
-#endif
-
-#ifdef CONFIG_SECURITY
- new->security = NULL;
-#endif
- if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)
- goto error;
- validate_creds(new);
-
- BUG_ON(atomic_read(&new->usage) != 1);
- return new;
-
-error:
- put_cred(new);
- return NULL;
-}
-
-/*
* Copy credentials for the new process created by fork()
*
* We share if we can, but under some circumstances we have to generate a new
--- mm/kernel/kmod.c~2_KILL_INFO_CRED 2010-02-26 20:18:48.000000000 +0100
+++ mm/kernel/kmod.c 2010-02-26 20:53:04.000000000 +0100
@@ -153,8 +153,6 @@ static int ____call_usermodehelper(void
struct subprocess_info *sub_info = data;
int retval;

- BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
-
/* Unblock all signals */
spin_lock_irq(&current->sighand->siglock);
flush_signal_handlers(current, 1);
@@ -162,10 +160,6 @@ static int ____call_usermodehelper(void
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);

- /* Install the credentials */
- commit_creds(sub_info->cred);
- sub_info->cred = NULL;
-
/* We can run anywhere, unlike our parent keventd(). */
set_cpus_allowed_ptr(current, cpu_all_mask);

@@ -193,8 +187,6 @@ void call_usermodehelper_freeinfo(struct
{
if (info->cleanup)
(*info->cleanup)(info);
- if (info->cred)
- put_cred(info->cred);
kfree(info);
}
EXPORT_SYMBOL(call_usermodehelper_freeinfo);
@@ -250,8 +242,6 @@ static void __call_usermodehelper(struct
pid_t pid;
enum umh_wait wait = sub_info->wait;

- BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
-
/* CLONE_VFORK: wait until the usermode helper has execve'd
* successfully We need the data structures to stay around
* until that is done. */
@@ -374,12 +364,6 @@ struct subprocess_info *call_usermodehel
sub_info->path = path;
sub_info->argv = argv;
sub_info->envp = envp;
- sub_info->cred = prepare_usermodehelper_creds();
- if (!sub_info->cred) {
- kfree(sub_info);
- return NULL;
- }
-
out:
return sub_info;
}
@@ -430,9 +414,6 @@ int call_usermodehelper_exec(struct subp
DECLARE_COMPLETION_ONSTACK(done);
int retval = 0;

- BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
- validate_creds(sub_info->cred);
-
helper_lock();
if (sub_info->path[0] == '\0')
goto out;


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