* [PATCH] [PATCH V2] tty: memleak in alloc_pid @ 2014-04-14 7:31 Chen Tingjie 2014-04-14 11:47 ` Greg Kroah-Hartman 0 siblings, 1 reply; 5+ messages in thread From: Chen Tingjie @ 2014-04-14 7:31 UTC (permalink / raw) To: Greg Kroah-Hartman, Jiri Slaby, linux-kernel; +Cc: Chen Tingjie, Zhang Jun There is memleak in alloc_pid: ------------------------------ unreferenced object 0xd3453a80 (size 64): comm "adbd", pid 1730, jiffies 66363 (age 6586.950s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 40 c2 f6 d5 00 d3 25 c1 59 28 00 00 ....@.....%.Y(.. backtrace: [<c1a6f15c>] kmemleak_alloc+0x3c/0xa0 [<c1320546>] kmem_cache_alloc+0xc6/0x190 [<c125d51e>] alloc_pid+0x1e/0x400 [<c123d344>] copy_process.part.39+0xad4/0x1120 [<c123da59>] do_fork+0x99/0x330 [<c123dd58>] sys_fork+0x28/0x30 [<c1a89a08>] syscall_call+0x7/0xb [<ffffffff>] 0xffffffff the leak is due to unreleased pid->count, which execute in function: get_pid()(pid->count++) and put_pid()(pid->count--). The race condition as following: task[dumpsys] task[adbd] in disassociate_ctty() in tty_signal_session_leader() ----------------------- ------------------------- tty = get_current_tty(); // tty is not NULL ... spin_lock_irq(¤t->sighand->siglock); put_pid(current->signal->tty_old_pgrp); current->signal->tty_old_pgrp = NULL; spin_unlock_irq(¤t->sighand->siglock); spin_lock_irq(&p->sighand->siglock); ... p->signal->tty = NULL; ... spin_unlock_irq(&p->sighand->siglock); tty = get_current_tty(); // tty NULL, goto else branch by accident. if (tty) { ... put_pid(tty_session); put_pid(tty_pgrp); ... } else { print msg } in task[dumpsys], in disassociate_ctty(), tty is set NULL by task[adbd], tty_signal_session_leader(), then it goto else branch and lack of put_pid(), cause memleak. move spin_unlock(sighand->siglock) after get_current_tty() can avoid the race and fix the memleak. Change-Id: Ic960dda039c8f99aad3e0f4d176489a966c62f6a Signed-off-by: Zhang Jun <jun.zhang@intel.com> Signed-off-by: Chen Tingjie <tingjie.chen@intel.com> --- drivers/tty/tty_io.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 31c4a57..72547a3 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -874,9 +874,8 @@ void disassociate_ctty(int on_exit) spin_lock_irq(¤t->sighand->siglock); put_pid(current->signal->tty_old_pgrp); current->signal->tty_old_pgrp = NULL; - spin_unlock_irq(¤t->sighand->siglock); - tty = get_current_tty(); + tty = tty_kref_get(current->signal->tty); if (tty) { unsigned long flags; spin_lock_irqsave(&tty->ctrl_lock, flags); @@ -893,6 +892,7 @@ void disassociate_ctty(int on_exit) #endif } + spin_unlock_irq(¤t->sighand->siglock); /* Now clear signal->tty under the lock */ read_lock(&tasklist_lock); session_clear_tty(task_session(current)); -- 1.7.9.5 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] [PATCH V2] tty: memleak in alloc_pid 2014-04-14 7:31 [PATCH] [PATCH V2] tty: memleak in alloc_pid Chen Tingjie @ 2014-04-14 11:47 ` Greg Kroah-Hartman 2014-04-15 2:49 ` Chen, Tingjie 0 siblings, 1 reply; 5+ messages in thread From: Greg Kroah-Hartman @ 2014-04-14 11:47 UTC (permalink / raw) To: Chen Tingjie; +Cc: Jiri Slaby, linux-kernel, Zhang Jun On Mon, Apr 14, 2014 at 03:31:15PM +0800, Chen Tingjie wrote: > There is memleak in alloc_pid: > ------------------------------ > unreferenced object 0xd3453a80 (size 64): > comm "adbd", pid 1730, jiffies 66363 (age 6586.950s) > hex dump (first 32 bytes): > 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 40 c2 f6 d5 00 d3 25 c1 59 28 00 00 ....@.....%.Y(.. > backtrace: > [<c1a6f15c>] kmemleak_alloc+0x3c/0xa0 > [<c1320546>] kmem_cache_alloc+0xc6/0x190 > [<c125d51e>] alloc_pid+0x1e/0x400 > [<c123d344>] copy_process.part.39+0xad4/0x1120 > [<c123da59>] do_fork+0x99/0x330 > [<c123dd58>] sys_fork+0x28/0x30 > [<c1a89a08>] syscall_call+0x7/0xb > [<ffffffff>] 0xffffffff > > the leak is due to unreleased pid->count, which execute in function: > get_pid()(pid->count++) and put_pid()(pid->count--). > > The race condition as following: > task[dumpsys] task[adbd] > in disassociate_ctty() in tty_signal_session_leader() > ----------------------- ------------------------- > tty = get_current_tty(); > // tty is not NULL > ... > spin_lock_irq(¤t->sighand->siglock); > put_pid(current->signal->tty_old_pgrp); > current->signal->tty_old_pgrp = NULL; > spin_unlock_irq(¤t->sighand->siglock); > > spin_lock_irq(&p->sighand->siglock); > ... > p->signal->tty = NULL; > ... > spin_unlock_irq(&p->sighand->siglock); > > tty = get_current_tty(); > // tty NULL, goto else branch by accident. > if (tty) { > ... > put_pid(tty_session); > put_pid(tty_pgrp); > ... > } else { > print msg > } > > in task[dumpsys], in disassociate_ctty(), tty is set NULL by task[adbd], > tty_signal_session_leader(), then it goto else branch and lack of > put_pid(), cause memleak. > > move spin_unlock(sighand->siglock) after get_current_tty() can avoid > the race and fix the memleak. > > Change-Id: Ic960dda039c8f99aad3e0f4d176489a966c62f6a Why is this line here? ^ permalink raw reply [flat|nested] 5+ messages in thread
* RE: [PATCH] [PATCH V2] tty: memleak in alloc_pid 2014-04-14 11:47 ` Greg Kroah-Hartman @ 2014-04-15 2:49 ` Chen, Tingjie 2014-04-15 2:54 ` Liu, Chuansheng 0 siblings, 1 reply; 5+ messages in thread From: Chen, Tingjie @ 2014-04-15 2:49 UTC (permalink / raw) To: Greg Kroah-Hartman Cc: Jiri Slaby, linux-kernel, Zhang, Jun, One Thousand Gnomes, Liu, Chuansheng Hello, The related code in disassociate_ctty() as following: --------------------------------------- /* sometimes current->signal->tty_old_pgrp is NULL (a stand for tty_old_pgrp not NULL, !a for tty_old_pgrp is NULL) */ spin_lock_irq(¤t->sighand->siglock); put_pid(current->signal->tty_old_pgrp); // when a is NULL, will not actually put_pid() by decrease the count current->signal->tty_old_pgrp = NULL; spin_unlock_irq(¤t->sighand->siglock); /* sometimes current->signal->tty is NULL (b stand for signal->tty, !b for signal->tty is NULL) */ tty = get_current_tty(); if (tty) { unsigned long flags; spin_lock_irqsave(&tty->ctrl_lock, flags); put_pid(tty->session); put_pid(tty->pgrp); tty->session = NULL; tty->pgrp = NULL; spin_unlock_irqrestore(&tty->ctrl_lock, flags); tty_kref_put(tty); } else { #ifdef TTY_DEBUG_HANGUP printk(KERN_DEBUG "error attempted to write to tty [0x%p]" " = NULL", tty); #endif } ------------------------------------ Commonly there are 2 normal case flow for the code: 1/ in task: getprop: !a --> b This case, current->signal->tty_old_pgrp is NULL, but get_current_tty() is not NULL, Really put_pid() as following: put_pid(tty->session); put_pid(tty->pgrp); 2/ in task: dumpsys: a --> !b This case, currnet->signal->tty_old_pgrp is not NULL, but get_current_tty() is NULL, Really put_pid() as following: put_pid(current->signal->tty_old_pgrp); There is one abnormal case: 3/ in task: dumpsys: !a -> !b This case, because of race, current->signal->tty_old_pgrp and get_current_tty() are NULL, Lack of put_pid(), pid->count will not be 0 at last, this pid will be leak. When read the current->signal->tty_old_pgrp and current->signal->tty, The 2 operations should be atomic, which protected by spinlock: current->sighand->siglock. So the sentence: spin_unlock_irq(¤t->sighand->siglock); need to move down after tty has process completed. Thanks, -----Original Message----- From: Greg Kroah-Hartman [mailto:gregkh@linuxfoundation.org] Sent: Monday, April 14, 2014 7:47 PM To: Chen, Tingjie Cc: Jiri Slaby; linux-kernel@vger.kernel.org; Zhang, Jun Subject: Re: [PATCH] [PATCH V2] tty: memleak in alloc_pid On Mon, Apr 14, 2014 at 03:31:15PM +0800, Chen Tingjie wrote: > There is memleak in alloc_pid: > ------------------------------ > unreferenced object 0xd3453a80 (size 64): > comm "adbd", pid 1730, jiffies 66363 (age 6586.950s) > hex dump (first 32 bytes): > 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 40 c2 f6 d5 00 d3 25 c1 59 28 00 00 ....@.....%.Y(.. > backtrace: > [<c1a6f15c>] kmemleak_alloc+0x3c/0xa0 > [<c1320546>] kmem_cache_alloc+0xc6/0x190 > [<c125d51e>] alloc_pid+0x1e/0x400 > [<c123d344>] copy_process.part.39+0xad4/0x1120 > [<c123da59>] do_fork+0x99/0x330 > [<c123dd58>] sys_fork+0x28/0x30 > [<c1a89a08>] syscall_call+0x7/0xb > [<ffffffff>] 0xffffffff > > the leak is due to unreleased pid->count, which execute in function: > get_pid()(pid->count++) and put_pid()(pid->count--). > > The race condition as following: > task[dumpsys] task[adbd] > in disassociate_ctty() in tty_signal_session_leader() > ----------------------- ------------------------- > tty = get_current_tty(); > // tty is not NULL > ... > spin_lock_irq(¤t->sighand->siglock); > put_pid(current->signal->tty_old_pgrp); > current->signal->tty_old_pgrp = NULL; > spin_unlock_irq(¤t->sighand->siglock); > > spin_lock_irq(&p->sighand->siglock); > ... > p->signal->tty = NULL; > ... > spin_unlock_irq(&p->sighand->siglock); > > tty = get_current_tty(); > // tty NULL, goto else branch by accident. > if (tty) { > ... > put_pid(tty_session); > put_pid(tty_pgrp); > ... > } else { > print msg > } > > in task[dumpsys], in disassociate_ctty(), tty is set NULL by > task[adbd], tty_signal_session_leader(), then it goto else branch and > lack of put_pid(), cause memleak. > > move spin_unlock(sighand->siglock) after get_current_tty() can avoid > the race and fix the memleak. > > Change-Id: Ic960dda039c8f99aad3e0f4d176489a966c62f6a Why is this line here? ^ permalink raw reply [flat|nested] 5+ messages in thread
* RE: [PATCH] [PATCH V2] tty: memleak in alloc_pid 2014-04-15 2:49 ` Chen, Tingjie @ 2014-04-15 2:54 ` Liu, Chuansheng 2014-04-15 3:02 ` Chen, Tingjie 0 siblings, 1 reply; 5+ messages in thread From: Liu, Chuansheng @ 2014-04-15 2:54 UTC (permalink / raw) To: Chen, Tingjie, Greg Kroah-Hartman Cc: Jiri Slaby, linux-kernel, Zhang, Jun, One Thousand Gnomes > > Change-Id: Ic960dda039c8f99aad3e0f4d176489a966c62f6a > > Why is this line here? Tingjie, Greg is asking you the sentence of "Change-Id", which is not needed, please remove it with one new patch. ^ permalink raw reply [flat|nested] 5+ messages in thread
* RE: [PATCH] [PATCH V2] tty: memleak in alloc_pid 2014-04-15 2:54 ` Liu, Chuansheng @ 2014-04-15 3:02 ` Chen, Tingjie 0 siblings, 0 replies; 5+ messages in thread From: Chen, Tingjie @ 2014-04-15 3:02 UTC (permalink / raw) To: Liu, Chuansheng, Greg Kroah-Hartman Cc: Jiri Slaby, linux-kernel, Zhang, Jun, One Thousand Gnomes > > Change-Id: Ic960dda039c8f99aad3e0f4d176489a966c62f6a > > > > Why is this line here? > Tingjie, Greg is asking you the sentence of "Change-Id", which is not needed, please remove it with one new patch. Sorry for mistaken, I will make a new patch for it. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2014-04-15 3:02 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2014-04-14 7:31 [PATCH] [PATCH V2] tty: memleak in alloc_pid Chen Tingjie 2014-04-14 11:47 ` Greg Kroah-Hartman 2014-04-15 2:49 ` Chen, Tingjie 2014-04-15 2:54 ` Liu, Chuansheng 2014-04-15 3:02 ` Chen, Tingjie
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