task->pid is only ever assigned once (well ok, twice). For system health and
secure logging confidence, make it const to make it much more intentional when
it is being changed.
---
Peter, as you had suggested, does this approach work for you in terms of making
task_struct::pid a lot more difficult to accidentally change to try to preserve
its integrity?
Is the use of memcpy() significantly different from *p = *q ?
arch/x86/kernel/process.c | 2 +-
fs/exec.c | 4 +++-
include/linux/sched.h | 2 +-
kernel/fork.c | 8 ++++++--
4 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index c83516b..4170026 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -66,7 +66,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct
task_struct *src)
{
int ret;
- *dst = *src;
+ memcpy(dst, src, sizeof(struct task_struct));
if (fpu_allocated(&src->thread.fpu)) {
memset(&dst->thread.fpu, 0, sizeof(dst->thread.fpu));
ret = fpu_alloc(&dst->thread.fpu);
diff --git a/fs/exec.c b/fs/exec.c
index 47d7edb..c8d0159 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -908,6 +908,8 @@ static int de_thread(struct task_struct *tsk)
*/
if (!thread_group_leader(tsk)) {
struct task_struct *leader = tsk->group_leader;
+ /* tast_struct::pid is const pid_t, hence the ugly cast */
+ pid_t *pid_p = (pid_t*)&(tsk->pid);
sig->notify_count = -1; /* for exit_notify() */
for (;;) {
@@ -950,7 +952,7 @@ static int de_thread(struct task_struct *tsk)
* Note: The old leader also uses this pid until release_task
* is called. Odd but simple and correct.
*/
- tsk->pid = leader->pid;
+ *pid_p = leader->pid;
change_pid(tsk, PIDTYPE_PID, task_pid(leader));
transfer_pid(leader, tsk, PIDTYPE_PGID);
transfer_pid(leader, tsk, PIDTYPE_SID);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index d9ada71..45069c0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1112,7 +1112,7 @@ struct task_struct {
unsigned sched_reset_on_fork:1;
unsigned sched_contributes_to_load:1;
- pid_t pid;
+ const pid_t pid;
pid_t tgid;
#ifdef CONFIG_CC_STACKPROTECTOR
diff --git a/kernel/fork.c b/kernel/fork.c
index 086fe73..ec0683d 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -286,7 +286,7 @@ void __init fork_init(unsigned long mempages)
int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
struct task_struct *src)
{
- *dst = *src;
+ memcpy(dst, src, sizeof(struct task_struct));
return 0;
}
@@ -1137,6 +1137,7 @@ static struct task_struct *copy_process(unsigned long
clone_flags,
{
int retval;
struct task_struct *p;
+ pid_t *pid_p;
if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
return ERR_PTR(-EINVAL);
@@ -1392,7 +1393,10 @@ static struct task_struct *copy_process(unsigned long
clone_flags,
clear_all_latency_tracing(p);
/* ok, now we should be set up.. */
- p->pid = pid_nr(pid);
+
+ /* tast_struct::pid is const pid_t, hence the ugly cast */
+ pid_p = (pid_t*)&(p->pid);
+ *pid_p = pid_nr(pid);
if (clone_flags & CLONE_THREAD) {
p->exit_signal = -1;
p->group_leader = current->group_leader;
--
1.7.1
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
