From 18976fa6125612d8c13d643c4a1a0269ed29e2c5 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Arkadiusz=20Mi=C5=9Bkiewicz?= Date: Sat, 26 Jan 2019 14:24:12 +0100 Subject: [PATCH] - rel 3; v2 version of the patch --- kernel-small_fixes.patch | 180 +++++++++++++++------------------------ kernel.spec | 2 +- 2 files changed, 71 insertions(+), 111 deletions(-) diff --git a/kernel-small_fixes.patch b/kernel-small_fixes.patch index 19610274..c210e451 100644 --- a/kernel-small_fixes.patch +++ b/kernel-small_fixes.patch @@ -162,113 +162,73 @@ index 76c92e31afc0..abb5d382f64d 100644 -- cgit 1.2-0.3.lf.el7 -From 48744b6339cf649a69b55997e138c17df1ecc897 Mon Sep 17 00:00:00 2001 -From: Tetsuo Handa -Date: Sat, 26 Jan 2019 20:00:51 +0900 -Subject: [PATCH] oom, oom_reaper: do not enqueue same task twice - -Arkadiusz reported that enabling memcg's group oom killing causes -strange memcg statistics where there is no task in a memcg despite -the number of tasks in that memcg is not 0. It turned out that there -is a bug in wake_oom_reaper() which allows enqueuing same task twice -which makes impossible to decrease the number of tasks in that memcg -due to a refcount leak. - -This bug existed since the OOM reaper became invokable from -task_will_free_mem(current) path in out_of_memory() in Linux 4.7, -but memcg's group oom killing made it easier to trigger this bug by -calling wake_oom_reaper() on the same task from one out_of_memory() -request. - -Fix this bug using an approach used by commit 855b018325737f76 -("oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task"). -Since task_will_free_mem(p) == false if p->mm == NULL, we can assume that -p->mm != NULL when wake_oom_reaper() is called from task_will_free_mem() -paths. As a side effect of this patch, this patch also avoids enqueuing -multiple threads sharing memory via task_will_free_mem(current) path. - -Signed-off-by: Tetsuo Handa -Reported-by: Arkadiusz Miśkiewicz -Fixes: af8e15cc85a25315 ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head") ---- - mm/oom_kill.c | 28 +++++++++++++--------------- - 1 file changed, 13 insertions(+), 15 deletions(-) - -diff --git a/mm/oom_kill.c b/mm/oom_kill.c -index f0e8cd9..457f240 100644 ---- a/mm/oom_kill.c -+++ b/mm/oom_kill.c -@@ -505,14 +505,6 @@ bool __oom_reap_task_mm(struct mm_struct *mm) - struct vm_area_struct *vma; - bool ret = true; - -- /* -- * Tell all users of get_user/copy_from_user etc... that the content -- * is no longer stable. No barriers really needed because unmapping -- * should imply barriers already and the reader would hit a page fault -- * if it stumbled over a reaped memory. -- */ -- set_bit(MMF_UNSTABLE, &mm->flags); -- - for (vma = mm->mmap ; vma; vma = vma->vm_next) { - if (!can_madv_dontneed_vma(vma)) - continue; -@@ -645,10 +637,15 @@ static int oom_reaper(void *unused) - return 0; - } - --static void wake_oom_reaper(struct task_struct *tsk) -+static void wake_oom_reaper(struct task_struct *tsk, struct mm_struct *mm) - { -- /* tsk is already queued? */ -- if (tsk == oom_reaper_list || tsk->oom_reaper_list) -+ /* -+ * Tell all users of get_user/copy_from_user etc... that the content -+ * is no longer stable. No barriers really needed because unmapping -+ * should imply barriers already and the reader would hit a page fault -+ * if it stumbled over a reaped memory. -+ */ -+ if (test_and_set_bit(MMF_UNSTABLE, &mm->flags)) - return; - - get_task_struct(tsk); -@@ -668,7 +665,8 @@ static int __init oom_init(void) - } - subsys_initcall(oom_init) - #else --static inline void wake_oom_reaper(struct task_struct *tsk) -+static inline void wake_oom_reaper(struct task_struct *tsk, -+ struct mm_struct *mm) - { - } - #endif /* CONFIG_MMU */ -@@ -915,7 +913,7 @@ static void __oom_kill_process(struct task_struct *victim) - rcu_read_unlock(); - - if (can_oom_reap) -- wake_oom_reaper(victim); -+ wake_oom_reaper(victim, mm); - - mmdrop(mm); - put_task_struct(victim); -@@ -955,7 +953,7 @@ static void oom_kill_process(struct oom_control *oc, const char *message) - task_lock(p); - if (task_will_free_mem(p)) { - mark_oom_victim(p); -- wake_oom_reaper(p); -+ wake_oom_reaper(p, p->mm); - task_unlock(p); - put_task_struct(p); - return; -@@ -1085,7 +1083,7 @@ bool out_of_memory(struct oom_control *oc) - */ - if (task_will_free_mem(current)) { - mark_oom_victim(current); -- wake_oom_reaper(current); -+ wake_oom_reaper(current, current->mm); - return true; - } - --- -1.8.3.1 - + +From 9c9e935fc038342c48461aabca666f1b544e32b1 Mon Sep 17 00:00:00 2001 +From: Tetsuo Handa +Date: Sat, 26 Jan 2019 21:57:25 +0900 +Subject: [PATCH v2] oom, oom_reaper: do not enqueue same task twice + +Arkadiusz reported that enabling memcg's group oom killing causes +strange memcg statistics where there is no task in a memcg despite +the number of tasks in that memcg is not 0. It turned out that there +is a bug in wake_oom_reaper() which allows enqueuing same task twice +which makes impossible to decrease the number of tasks in that memcg +due to a refcount leak. + +This bug existed since the OOM reaper became invokable from +task_will_free_mem(current) path in out_of_memory() in Linux 4.7, +but memcg's group oom killing made it easier to trigger this bug by +calling wake_oom_reaper() on the same task from one out_of_memory() +request. + +Fix this bug using an approach used by commit 855b018325737f76 +("oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task"). +As a side effect of this patch, this patch also avoids enqueuing +multiple threads sharing memory via task_will_free_mem(current) path. + +Signed-off-by: Tetsuo Handa +Reported-by: Arkadiusz Miśkiewicz +Tested-by: Arkadiusz Miśkiewicz +Fixes: af8e15cc85a25315 ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head") +--- + mm/oom_kill.c | 17 +++++++---------- + 1 file changed, 7 insertions(+), 10 deletions(-) + +diff --git a/mm/oom_kill.c b/mm/oom_kill.c +index f0e8cd9..057bfee 100644 +--- a/mm/oom_kill.c ++++ b/mm/oom_kill.c +@@ -505,14 +505,6 @@ bool __oom_reap_task_mm(struct mm_struct *mm) + struct vm_area_struct *vma; + bool ret = true; + +- /* +- * Tell all users of get_user/copy_from_user etc... that the content +- * is no longer stable. No barriers really needed because unmapping +- * should imply barriers already and the reader would hit a page fault +- * if it stumbled over a reaped memory. +- */ +- set_bit(MMF_UNSTABLE, &mm->flags); +- + for (vma = mm->mmap ; vma; vma = vma->vm_next) { + if (!can_madv_dontneed_vma(vma)) + continue; +@@ -647,8 +639,13 @@ static int oom_reaper(void *unused) + + static void wake_oom_reaper(struct task_struct *tsk) + { +- /* tsk is already queued? */ +- if (tsk == oom_reaper_list || tsk->oom_reaper_list) ++ /* ++ * Tell all users of get_user/copy_from_user etc... that the content ++ * is no longer stable. No barriers really needed because unmapping ++ * should imply barriers already and the reader would hit a page fault ++ * if it stumbled over a reaped memory. ++ */ ++ if (test_and_set_bit(MMF_UNSTABLE, &tsk->signal->oom_mm->flags)) + return; + + get_task_struct(tsk); +-- +1.8.3.1 + diff --git a/kernel.spec b/kernel.spec index 166a18e1..16f7c40e 100644 --- a/kernel.spec +++ b/kernel.spec @@ -67,7 +67,7 @@ %define have_pcmcia 0 %endif -%define rel 2 +%define rel 3 %define basever 4.20 %define postver .3 -- 2.44.0