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authorChen Tingjie <tingjie.chen@intel.com>2014-04-15 07:52:51 +0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-04-17 01:31:13 +0400
commitc70dbb1e79a1ac2802b4b7b6de7456b230fbbbeb (patch)
tree5ecb61ba932bb1cdefdee633a02bd896ceade4f6 /drivers/tty
parentb24313a82cf24e90170671ea74360b3e6ef3a91f (diff)
downloadlinux-c70dbb1e79a1ac2802b4b7b6de7456b230fbbbeb.tar.xz
tty: fix memleak in alloc_pid
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(&current->sighand->siglock); put_pid(current->signal->tty_old_pgrp); current->signal->tty_old_pgrp = NULL; spin_unlock_irq(&current->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. Signed-off-by: Zhang Jun <jun.zhang@intel.com> Signed-off-by: Chen Tingjie <tingjie.chen@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/tty_io.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index d3448a90f0f9..34110719fe03 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -878,9 +878,8 @@ void disassociate_ctty(int on_exit)
spin_lock_irq(&current->sighand->siglock);
put_pid(current->signal->tty_old_pgrp);
current->signal->tty_old_pgrp = NULL;
- spin_unlock_irq(&current->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);
@@ -897,6 +896,7 @@ void disassociate_ctty(int on_exit)
#endif
}
+ spin_unlock_irq(&current->sighand->siglock);
/* Now clear signal->tty under the lock */
read_lock(&tasklist_lock);
session_clear_tty(task_session(current));