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(¤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. 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>
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