signals: move cred_guard_mutex from task_struct to signal_struct

Oleg Nesterov pointed out we have to prevent multiple-threads-inside-exec
itself and we can reuse ->cred_guard_mutex for it.  Yes, concurrent
execve() has no worth.

Let's move ->cred_guard_mutex from task_struct to signal_struct.  It
naturally prevent multiple-threads-inside-exec.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KOSAKI Motohiro 2010-10-27 15:34:08 -07:00 • committed by Linus Torvalds
commit 9b1bf12d5d
8 changed files with 21 additions and 20 deletions

View file

@ -29,6 +29,8 @@ extern struct fs_struct init_fs;
.running = 0, \
.lock = __SPIN_LOCK_UNLOCKED(sig.cputimer.lock), \
}, \
.cred_guard_mutex = \
__MUTEX_INITIALIZER(sig.cred_guard_mutex), \
}
extern struct nsproxy init_nsproxy;
@ -145,8 +147,6 @@ extern struct cred init_cred;
.group_leader = &tsk, \
RCU_INIT_POINTER(.real_cred, &init_cred), \
RCU_INIT_POINTER(.cred, &init_cred), \
.cred_guard_mutex = \
__MUTEX_INITIALIZER(tsk.cred_guard_mutex), \
.comm = "swapper", \
.thread = INIT_THREAD, \
.fs = &init_fs, \

View file

@ -626,6 +626,10 @@ struct signal_struct {
int oom_adj; /* OOM kill score adjustment (bit shift) */
int oom_score_adj; /* OOM kill score adjustment */
struct mutex cred_guard_mutex; /* guard against foreign influences on
* credential calculations
* (notably. ptrace) */
};
/* Context switch must be unlocked if interrupts are to be enabled */
@ -1305,9 +1309,6 @@ struct task_struct {
* credentials (COW) */
const struct cred __rcu *cred; /* effective (overridable) subjective task
* credentials (COW) */
struct mutex cred_guard_mutex; /* guard against foreign influences on
* credential calculations
* (notably. ptrace) */
struct cred *replacement_session_keyring; /* for KEYCTL_SESSION_TO_PARENT */
char comm[TASK_COMM_LEN]; /* executable name excluding path

View file

@ -150,7 +150,7 @@ static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
*
* Return %LSM_UNSAFE_* bits applied to an exec because of tracing.
*
* @task->cred_guard_mutex is held by the caller through the do_execve().
* @task->signal->cred_guard_mutex is held by the caller through the do_execve().
*/
static inline int tracehook_unsafe_exec(struct task_struct *task)
{