On 11/16, Oleg Nesterov wrote:
>
> And I didn't check "make xcheck", I guess it still crashes the kernel.
Yes it does. I am almost sure the bug should be trivial, but
somehow can't find find it. Just fyi, to ensure this is connected
to utrace-indirect I applied the hack below and the bug goes away.
OK. Tomorrow I will just read utrace.c trying to understand the
details of the new code, perhaps I will notice something.
Oleg.
--- UTRACE-PTRACE/kernel/fork.c~XXX_CRASH 2009-11-16 20:26:23.000000000
+0100
+++ UTRACE-PTRACE/kernel/fork.c 2009-11-16 21:18:57.000000000 +0100
@@ -970,6 +970,8 @@ static void posix_cpu_timers_init(struct
* parts of the process environment (as per the clone
* flags). The actual kick-off is left to the caller.
*/
+bool utrace_task_alloc(struct task_struct *task);
+
static struct task_struct *copy_process(unsigned long clone_flags,
unsigned long stack_start,
struct pt_regs *regs,
@@ -1227,6 +1229,10 @@ static struct task_struct *copy_process(
cgroup_fork_callbacks(p);
cgroup_callbacks_done = 1;
+ p->utrace = NULL;
+ if (!utrace_task_alloc(p))
+ WARN_ON(1);
+
/* Need tasklist lock for parent etc handling! */
write_lock_irq(&tasklist_lock);
--- UTRACE-PTRACE/kernel/utrace.c~XXX_CRASH 2009-11-16 20:31:38.000000000
+0100
+++ UTRACE-PTRACE/kernel/utrace.c 2009-11-16 21:19:26.000000000 +0100
@@ -87,9 +87,9 @@ module_init(utrace_init);
*
* This returns false only in case of a memory allocation failure.
*/
-static bool utrace_task_alloc(struct task_struct *task)
+bool utrace_task_alloc(struct task_struct *task)
{
- struct utrace *utrace = kmem_cache_zalloc(utrace_cachep, GFP_KERNEL);
+ struct utrace *utrace = kzalloc(sizeof(struct utrace), GFP_KERNEL);
if (unlikely(!utrace))
return false;
spin_lock_init(&utrace->lock);
@@ -108,7 +108,7 @@ static bool utrace_task_alloc(struct tas
}
task_unlock(task);
if (unlikely(task->utrace != utrace))
- kmem_cache_free(utrace_cachep, utrace);
+ kfree(utrace);
return true;
}
@@ -118,7 +118,7 @@ static bool utrace_task_alloc(struct tas
*/
void utrace_free_task(struct task_struct *task)
{
- kmem_cache_free(utrace_cachep, task->utrace);
+ kfree(task->utrace);
}
/*
@@ -286,6 +286,8 @@ struct utrace_engine *utrace_attach_task
struct utrace_engine *engine;
int ret;
+ WARN_ON(!utrace);
+
if (!(flags & UTRACE_ATTACH_CREATE)) {
if (unlikely(!utrace))
return ERR_PTR(-ENOENT);
--- UTRACE-PTRACE/include/linux/utrace.h~XXX_CRASH 2009-11-16
01:06:34.000000000 +0100
+++ UTRACE-PTRACE/include/linux/utrace.h 2009-11-16 20:50:38.000000000
+0100
@@ -163,7 +163,7 @@ static inline struct utrace *task_utrace
static inline void utrace_init_task(struct task_struct *task)
{
task->utrace_flags = 0;
- task->utrace = NULL;
+ WARN_ON(!task->utrace);
}
void utrace_release_task(struct task_struct *);
