Messages in this thread Patch in this message |  | | Date | Thu, 7 Sep 2006 02:38:38 +0400 | | From | Oleg Nesterov <> | | Subject | [PATCH] proc-readdir-race-fix-take-3-fix-3 |
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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 <oleg@tv-sign.ru>
--- 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; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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