hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I7LEZX -------------------------------- There is memleak in alloc_pid: ------------------------------ unreferenced object 0xffff88810c181940 (size 224): comm "sshd", pid 8191, jiffies 4294946950 (age 524.570s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 00 00 00 00 ad 4e ad de .............N.. ff ff ff ff 6b 6b 6b 6b ff ff ff ff ff ff ff ff ....kkkk........ backtrace: [<ffffffff814774e6>] kmem_cache_alloc+0x5c6/0x9b0 [<ffffffff81177342>] alloc_pid+0x72/0x570 [<ffffffff81140ac4>] copy_process+0x1374/0x2470 [<ffffffff81141d77>] kernel_clone+0xb7/0x900 [<ffffffff81142645>] __se_sys_clone+0x85/0xb0 [<ffffffff8114269b>] __x64_sys_clone+0x2b/0x30 [<ffffffff83965a72>] do_syscall_64+0x32/0x80 [<ffffffff83a00085>] entry_SYSCALL_64_after_hwframe+0x61/0xc6 The pid memleak is triggered by the following race: task[sshd] task[bash] ----------------------- ----------------------- do_exit(); disassociate_ctty(); spin_lock_irq(¤t->sighand->siglock); put_pid(current->signal->tty_old_pgrp); current->signal->tty_old_pgrp = NULL; tty = tty_kref_get(current->signal->tty); //tty is not NULL spin_unlock_irq(¤t->sighand->siglock); tty_vhangup(); tty_lock(tty); ... tty_signal_session_leader(); spin_lock_irq(&p->sighand->siglock); ... p->signal->tty_old_pgrp = get_pid(tty->pgrp); // tty_old_pgrp reassign spin_unlock_irq(&p->sighand->siglock); ... tty_unlock(tty); if (tty) { tty_lock(tty); ... put_pid(tty->pgrp); tty->pgrp = NULL;// It's too late ... tty_unlock(tty); } in task[bash], tty_old_pgrp is released by disassociate_ctty(), then it's reassigned by tty_signal_session_leader() in task[sshd], cause memleak. fix the memleak by add put_pid() in disassociate_ctty() after tty_old_pgrp is reassigned. Fixes: c8bcd9c5be24 ("tty: Fix ->session locking") Signed-off-by: Yi Yang <yiyang13@huawei.com> --- drivers/tty/tty_jobctrl.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/tty/tty_jobctrl.c b/drivers/tty/tty_jobctrl.c index aa6d0537b379..56c791c81b4f 100644 --- a/drivers/tty/tty_jobctrl.c +++ b/drivers/tty/tty_jobctrl.c @@ -308,6 +308,18 @@ void disassociate_ctty(int on_exit) spin_unlock_irqrestore(&tty->ctrl_lock, flags); tty_unlock(tty); tty_kref_put(tty); + + /* + * Race with tty_signal_session_leader(), current->signal + * ->tty_old_pgrp may be reassigned, put_pid() again to ensure + * the pid does not leak memory. + */ + if (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); + } } /* Now clear signal->tty under the lock */ -- 2.17.1