Messages in this thread Patch in this message | | | Subject | PATCH] fix current->user->__count leak for processes | From | Arvind Kandhare <> | Date | 03 Jul 2003 11:34:19 +0530 |
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Hi, I am trying to test a patch for limiting maximum number of users on the system(refer: [RFC][PATCH 2.5.70] Dynamically tunable maxusers, maxuprc and max_pt_cnt on 06 Jun 2003).
I stumbled across this problem : when switch_uid is called, the reference count of the new user is incremented twice. I think the increment in the switch_uid is done because of the reparent_to_init() function which does not increase the __count for root user.
But if switch_uid is called from any other function, the reference count is already incremented by the caller by calling alloc_uid for the new user. Hence the count is incremented twice. The user struct will not be deleted even when there are no processes holding a reference count for it. This does not cause any problem currently because nothing is dependent on timely deletion of the user struct.
Here is a small patch to solve this problem.
Thanks and regards, Arvind
diff -Naur linux-2.5.73/kernel/exit.c linux-2.5.73.n/kernel/exit.c --- linux-2.5.73/kernel/exit.c 2003-06-23 00:03:15.000000000 +0530 +++ linux-2.5.73.n/kernel/exit.c 2003-07-03 10:48:32.000000000 +0530 @@ -230,6 +230,7 @@ /* signals? */ security_task_reparent_to_init(current); memcpy(current->rlim, init_task.rlim, sizeof(*(current->rlim))); + atomic_inc(&(INIT_USER->__count)); switch_uid(INIT_USER); write_unlock_irq(&tasklist_lock); diff -Naur linux-2.5.73/kernel/user.c linux-2.5.73.n/kernel/user.c --- linux-2.5.73/kernel/user.c 2003-06-23 00:02:41.000000000 +0530 +++ linux-2.5.73.n/kernel/user.c 2003-07-03 10:46:59.000000000 +0530 @@ -126,7 +126,6 @@ * we should be checking for it. -DaveM */ old_user = current->user; - atomic_inc(&new_user->__count); atomic_inc(&new_user->processes); atomic_dec(&old_user->processes); current->user = new_user;
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