From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gaurav Kohli Subject: [PATCH] mm: oom: Fix race condition between oom_badness and do_exit of task Date: Wed, 7 Mar 2018 18:27:34 +0530 Message-ID: <1520427454-22813-1-git-send-email-gkohli@codeaurora.org> Return-path: Sender: linux-kernel-owner@vger.kernel.org To: akpm@linux-foundation.org, mhocko@suse.com, rientjes@google.com, kirill.shutemov@linux.intel.com, aarcange@redhat.com, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, Gaurav Kohli List-Id: linux-arm-msm@vger.kernel.org oom_badness access real_cred of task for calculation without increasing the usage counter of task struct. This may create a race if do_exit of same task runs and free the real_cred. So using get_task_struct which blocks the freeing until oom_badness is executing. el1_da+0x24/0x84 security_capable_noaudit+0x64/0x94 has_capability_noaudit+0x38/0x58 oom_badness.part.21+0x114/0x1c0 oom_badness+0x50/0x5c proc_oom_score+0x48/0x80 proc_single_show+0x5c/0xb8 Signed-off-by: Gaurav Kohli diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 6fd9773..5f4cc4b 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -114,9 +114,11 @@ struct task_struct *find_lock_task_mm(struct task_struct *p) for_each_thread(p, t) { task_lock(t); + get_task_struct(t); if (likely(t->mm)) goto found; task_unlock(t); + put_task_struct(t); } t = NULL; found: @@ -191,6 +193,7 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, test_bit(MMF_OOM_SKIP, &p->mm->flags) || in_vfork(p)) { task_unlock(p); + put_task_struct(p); return 0; } @@ -208,7 +211,7 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, */ if (has_capability_noaudit(p, CAP_SYS_ADMIN)) points -= (points * 3) / 100; - + put_task_struct(p); /* Normalize to oom_score_adj units */ adj *= totalpages / 1000; points += adj; -- 1.9.1