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CRED: Rename cred_exec_mutex to reflect that it's a guard against ptrace

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Rename cred_exec_mutex to reflect that it's a guard against foreign
intervention on a process's credential state, such as is made by ptrace().  The
attachment of a debugger to a process affects execve()'s calculation of the new
credential state - _and_ also setprocattr()'s calculation of that state.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
David Howells 2009-05-08 13:55:22 +01:00 committed by James Morris
parent d254117099
commit 5e751e992f
6 changed files with 20 additions and 17 deletions
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6
fs/compat.c
View file

@ -1488,7 +1488,7 @@ int compat_do_execve(char * filename,
if (!bprm)
goto out_files;
retval = mutex_lock_interruptible(&current->cred_exec_mutex);
retval = mutex_lock_interruptible(&current->cred_guard_mutex);
if (retval < 0)
goto out_free;
current->in_execve = 1;
@ -1550,7 +1550,7 @@ int compat_do_execve(char * filename,
/* execve succeeded */
current->fs->in_exec = 0;
current->in_execve = 0;
mutex_unlock(&current->cred_exec_mutex);
mutex_unlock(&current->cred_guard_mutex);
acct_update_integrals(current);
free_bprm(bprm);
if (displaced)
@ -1573,7 +1573,7 @@ out_unmark:
out_unlock:
current->in_execve = 0;
mutex_unlock(&current->cred_exec_mutex);
mutex_unlock(&current->cred_guard_mutex);
out_free:
free_bprm(bprm);

10
fs/exec.c
View file

@ -1045,7 +1045,7 @@ void install_exec_creds(struct linux_binprm *bprm)
commit_creds(bprm->cred);
bprm->cred = NULL;
/* cred_exec_mutex must be held at least to this point to prevent
/* cred_guard_mutex must be held at least to this point to prevent
* ptrace_attach() from altering our determination of the task's
* credentials; any time after this it may be unlocked */
@ -1055,7 +1055,7 @@ EXPORT_SYMBOL(install_exec_creds);
/*
* determine how safe it is to execute the proposed program
* - the caller must hold current->cred_exec_mutex to protect against
* - the caller must hold current->cred_guard_mutex to protect against
* PTRACE_ATTACH
*/
int check_unsafe_exec(struct linux_binprm *bprm)
@ -1297,7 +1297,7 @@ int do_execve(char * filename,
if (!bprm)
goto out_files;
retval = mutex_lock_interruptible(&current->cred_exec_mutex);
retval = mutex_lock_interruptible(&current->cred_guard_mutex);
if (retval < 0)
goto out_free;
current->in_execve = 1;
@ -1360,7 +1360,7 @@ int do_execve(char * filename,
/* execve succeeded */
current->fs->in_exec = 0;
current->in_execve = 0;
mutex_unlock(&current->cred_exec_mutex);
mutex_unlock(&current->cred_guard_mutex);
acct_update_integrals(current);
free_bprm(bprm);
if (displaced)
@ -1383,7 +1383,7 @@ out_unmark:
out_unlock:
current->in_execve = 0;
mutex_unlock(&current->cred_exec_mutex);
mutex_unlock(&current->cred_guard_mutex);
out_free:
free_bprm(bprm);

4
include/linux/init_task.h
View file

@ -145,8 +145,8 @@ extern struct cred init_cred;
.group_leader = &tsk, \
.real_cred = &init_cred, \
.cred = &init_cred, \
.cred_exec_mutex = \
__MUTEX_INITIALIZER(tsk.cred_exec_mutex), \
.cred_guard_mutex = \
__MUTEX_INITIALIZER(tsk.cred_guard_mutex), \
.comm = "swapper", \
.thread = INIT_THREAD, \
.fs = &init_fs, \

4
include/linux/sched.h
View file

@ -1247,7 +1247,9 @@ struct task_struct {
* credentials (COW) */
const struct cred *cred; /* effective (overridable) subjective task
* credentials (COW) */
struct mutex cred_exec_mutex; /* execve vs ptrace cred calculation mutex */
struct mutex cred_guard_mutex; /* guard against foreign influences on
* credential calculations
* (notably. ptrace) */
char comm[TASK_COMM_LEN]; /* executable name excluding path
- access with [gs]et_task_comm (which lock

4
kernel/cred.c
View file

@ -167,7 +167,7 @@ EXPORT_SYMBOL(prepare_creds);
/*
* Prepare credentials for current to perform an execve()
* - The caller must hold current->cred_exec_mutex
* - The caller must hold current->cred_guard_mutex
*/
struct cred *prepare_exec_creds(void)
{
@ -276,7 +276,7 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags)
struct cred *new;
int ret;
mutex_init(&p->cred_exec_mutex);
mutex_init(&p->cred_guard_mutex);
if (
#ifdef CONFIG_KEYS

9
kernel/ptrace.c
View file

@ -185,10 +185,11 @@ int ptrace_attach(struct task_struct *task)
if (same_thread_group(task, current))
goto out;
/* Protect exec's credential calculations against our interference;
* SUID, SGID and LSM creds get determined differently under ptrace.
/* Protect the target's credential calculations against our
* interference; SUID, SGID and LSM creds get determined differently
* under ptrace.
*/
retval = mutex_lock_interruptible(&task->cred_exec_mutex);
retval = mutex_lock_interruptible(&task->cred_guard_mutex);
if (retval < 0)
goto out;
@ -232,7 +233,7 @@ repeat:
bad:
write_unlock_irqrestore(&tasklist_lock, flags);
task_unlock(task);
mutex_unlock(&task->cred_exec_mutex);
mutex_unlock(&task->cred_guard_mutex);
out:
return retval;
}