[PATCH 1/2] CRED: Rename cred_exec_mutex to reflect that it's a guardagainst ptrace

From: David Howells
Date: Fri May 08 2009 - 08:58:40 EST

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@xxxxxxxxxx>
---

fs/compat.c | 6 +++---
fs/exec.c | 10 +++++-----
include/linux/init_task.h | 4 ++--
include/linux/sched.h | 4 +++-
kernel/cred.c | 4 ++--
kernel/ptrace.c | 9 +++++----
6 files changed, 20 insertions(+), 17 deletions(-)


diff --git a/fs/compat.c b/fs/compat.c
index 681ed81..bb2a9b2 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -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);
diff --git a/fs/exec.c b/fs/exec.c
index 639177b..998e856 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -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);
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index d87247d..7f54ba9 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -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, \
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3fa82b3..5932ace 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -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
diff --git a/kernel/cred.c b/kernel/cred.c
index 3a03918..1bb4d7e 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -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
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 0692ab5..27ac802 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -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;
}

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/