On 09/07, Oleg Nesterov wrote:
>
> On 09/06, Jean Delvare wrote:
> >
> > On Wednesday 6 September 2006 11:01, Jean Delvare wrote:
> > > Eric, Kame, thanks a lot for working on this. I'll be giving some good
> > > testing to this patch today, and will return back to you when I'm done.
> >
> > The original issue is indeed fixed, but there's a problem with the patch.
> > When stressing /proc (to verify the bug was fixed), my test machine ended
> > up crashing. Here are the 2 traces I found in the logs:
> >
> > Sep 6 12:06:00 arrakis kernel: BUG: warning at
> > kernel/fork.c:113/__put_task_struct()
> > Sep 6 12:06:00 arrakis kernel: [<c0115f93>] __put_task_struct+0xf3/0x100
> > Sep 6 12:06:00 arrakis kernel: [<c019666a>] proc_pid_readdir+0x13a/0x150
> > Sep 6 12:06:00 arrakis kernel: [<c01745f0>] vfs_readdir+0x80/0xa0
> > Sep 6 12:06:00 arrakis kernel: [<c0174750>] filldir+0x0/0xd0
> > Sep 6 12:06:00 arrakis kernel: [<c017488c>] sys_getdents+0x6c/0xb0
> > Sep 6 12:06:00 arrakis kernel: [<c0174750>] filldir+0x0/0xd0
> > Sep 6 12:06:00 arrakis kernel: [<c0102fb7>] syscall_call+0x7/0xb
>
> If the task found is not a group leader, we go to retry, but
> the task != NULL.
>
> Now, if find_ge_pid(tgid) returns NULL, we return that wrong
> task, and it was not get_task_struct()'ed.
Signed-off-by: Oleg Nesterov <[email protected]>
--- t/fs/proc/base.c~ 2006-09-07 02:33:26.000000000 +0400
+++ t/fs/proc/base.c 2006-09-07 02:34:19.000000000 +0400
@@ -2149,9 +2149,9 @@ static struct task_struct *next_tgid(uns
struct task_struct *task;
struct pid *pid;
- task = NULL;
rcu_read_lock();
retry:
+ task = NULL;
pid = find_ge_pid(tgid);
if (pid) {
tgid = pid->nr + 1;
-
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