linux-kernel - [PATCH -next] posix-cpu-timers: fix memory leaks for task

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Message-Id: <20200304004336.960-1-cai@lca.pw>
Date:   Tue,  3 Mar 2020 19:43:36 -0500
From:   Qian Cai <cai@....pw>
To:     tglx@...utronix.de
Cc:     ebiederm@...ssion.com, oleg@...hat.com,
        linux-kernel@...r.kernel.org, Qian Cai <cai@....pw>
Subject: [PATCH -next] posix-cpu-timers: fix memory leaks for task_struct

The recent commit removed put_task_struct() in posix_cpu_timer_del()
results in many memory leaks like this,

unreferenced object 0xc0000016d9b44480 (size 8192):
  comm "timer_create01", pid 57749, jiffies 4295163733 (age 6159.670s)
  hex dump (first 32 bytes):
    02 00 00 00 00 00 00 00 10 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<0000000056aca129>] copy_process+0x26c/0x18e0
    alloc_task_struct_node at kernel/fork.c:169
    (inlined by) dup_task_struct at kernel/fork.c:877
    (inlined by) copy_process at kernel/fork.c:1929
    [<00000000bdbbf9f8>] _do_fork+0xac/0xb20
    [<00000000dcb1c445>] __do_sys_clone+0x98/0xe0
    __do_sys_clone at kernel/fork.c:2591
    [<000000006c059205>] ppc_clone+0x8/0xc
    ppc_clone at arch/powerpc/kernel/entry_64.S:479

Fixes: 672ebe8eb017a5 ("posix-cpu-timers: Store a reference to a pid not a task")
Signed-off-by: Qian Cai <cai@....pw>
---
 kernel/time/posix-cpu-timers.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index afd1e959a282..e0b580deb61a 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -446,8 +446,10 @@ static int posix_cpu_timer_del(struct k_itimer *timer)
 
 out:
 	rcu_read_unlock();
-	if (!ret)
+	if (!ret) {
 		put_pid(ctmr->pid);
+		put_task_struct(p);
+	}
 
 	return ret;
 }
-- 
2.21.0 (Apple Git-122.2)