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Date: Mon, 27 Jul 2009 09:27:18 +0900
From: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
To: Oleg Nesterov <oleg@...hat.com>
CC: Roland McGrath <roland@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] task_struct cleanup: move binfmt field to mm_struct
Oleg Nesterov wrote:
> On 07/24, Hiroshi Shimamoto wrote:
>> int set_binfmt(struct linux_binfmt *new)
>> {
>> - struct linux_binfmt *old = current->binfmt;
>> + struct linux_binfmt *old;
>>
>> + if (!current->mm)
>> + return -1;
>> +
>> + old = current->mm->binfmt;
>> if (new) {
>> if (!try_module_get(new->module))
>> return -1;
>> }
>> - current->binfmt = new;
>> + current->mm->binfmt = new;
>
> Hmm. Of-topic, but I think set_binfmt() is buggy (with or without this patch),
> it should use __module_get(). I'll send the fix in a minute.
>
>> @@ -1730,7 +1734,7 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
>>
>> audit_core_dumps(signr);
>>
>> - binfmt = current->binfmt;
>> + binfmt = current->mm ? current->mm->binfmt : NULL;
>
> current->mm can't be NULL here. And please note we already have
> struct mm_struct *mm = current->mm, so the above should be
>
> binfmt = mm->binfmt;
>
>> @@ -953,6 +953,9 @@ NORET_TYPE void do_exit(long code)
>> tsk->exit_code = code;
>> taskstats_exit(tsk, group_dead);
>>
>> + if (tsk->mm && tsk->mm->binfmt)
>> + module_put(tsk->mm->binfmt->module);
>
> This is not right. We leak ->binfmt on exec.
>
> Seems to be fixed by the next patch, but still this is not good.
> I'd suggest you to merge these 2 patches into single patch, because
> module_put(->binfmt) should go to mmput() from the very beginning.
Hi Oleg, thank you very much for comments, here is an update patch.
This patch can be applied after your set_binfmt() fix.
========
From: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
Subject: [PATCH] task_struct cleanup: move binfmt field to mm_struct
Because the binfmt is not different between threads in the same process,
it can be moved from task_struct to mm_struct. And binfmt moudle is handled
per mm_struct instead of task_struct.
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
---
fs/exec.c | 11 +++++++----
include/linux/mm_types.h | 2 ++
include/linux/sched.h | 1 -
kernel/exit.c | 2 --
kernel/fork.c | 11 +++++------
5 files changed, 14 insertions(+), 13 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index 61d5be2..41aea26 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1377,10 +1377,13 @@ out_ret:
void set_binfmt(struct linux_binfmt *new)
{
- if (current->binfmt)
- module_put(current->binfmt->module);
+ struct mm_struct *mm = current->mm;
+
+ BUG_ON(!mm);
+ if (mm->binfmt)
+ module_put(mm->binfmt->module);
- current->binfmt = new;
+ mm->binfmt = new;
if (new)
__module_get(new->module);
}
@@ -1726,7 +1729,7 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
audit_core_dumps(signr);
- binfmt = current->binfmt;
+ binfmt = mm->binfmt;
if (!binfmt || !binfmt->core_dump)
goto fail;
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 7acc843..6719040 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -240,6 +240,8 @@ struct mm_struct {
unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */
+ struct linux_binfmt *binfmt;
+
s8 oom_adj; /* OOM kill score adjustment (bit shift) */
cpumask_t cpu_vm_mask;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3ab08e4..940b070 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1220,7 +1220,6 @@ struct task_struct {
struct mm_struct *mm, *active_mm;
/* task state */
- struct linux_binfmt *binfmt;
int exit_state;
int exit_code, exit_signal;
int pdeath_signal; /* The signal sent when the parent dies */
diff --git a/kernel/exit.c b/kernel/exit.c
index 869dc22..77b01be 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -970,8 +970,6 @@ NORET_TYPE void do_exit(long code)
disassociate_ctty(1);
module_put(task_thread_info(tsk)->exec_domain->module);
- if (tsk->binfmt)
- module_put(tsk->binfmt->module);
proc_exit_connector(tsk);
diff --git a/kernel/fork.c b/kernel/fork.c
index 9b42695..9c21984 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -494,6 +494,8 @@ void mmput(struct mm_struct *mm)
spin_unlock(&mmlist_lock);
}
put_swap_token(mm);
+ if (mm->binfmt)
+ module_put(mm->binfmt->module);
mmdrop(mm);
}
}
@@ -619,6 +621,9 @@ struct mm_struct *dup_mm(struct task_struct *tsk)
mm->hiwater_rss = get_mm_rss(mm);
mm->hiwater_vm = mm->total_vm;
+ if (mm->binfmt && !try_module_get(mm->binfmt->module))
+ goto free_pt;
+
return mm;
free_pt:
@@ -1013,9 +1018,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
if (!try_module_get(task_thread_info(p)->exec_domain->module))
goto bad_fork_cleanup_count;
- if (p->binfmt && !try_module_get(p->binfmt->module))
- goto bad_fork_cleanup_put_domain;
-
p->did_exec = 0;
delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
copy_flags(clone_flags, p);
@@ -1300,9 +1302,6 @@ bad_fork_cleanup_cgroup:
#endif
cgroup_exit(p, cgroup_callbacks_done);
delayacct_tsk_free(p);
- if (p->binfmt)
- module_put(p->binfmt->module);
-bad_fork_cleanup_put_domain:
module_put(task_thread_info(p)->exec_domain->module);
bad_fork_cleanup_count:
atomic_dec(&p->cred->user->processes);
--
1.6.3.3
--
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