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Commit 8345bad0 authored by Ashwini Oruganti's avatar Ashwini Oruganti Committed by Pranav Vashi
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Revert "mm: oom_kill: reap memory of a task that receives SIGKILL" 

This reverts commit 724adb44.

Reason for revert: The changes introduced in this commit are causing an
undesirable SELinux denial as a side-effect. Additionally, it appears
(http://b/130391762

) that we do not enable the functionality that this
commit adds. Reverting the commit fixes the SELinux denial bug.

Bug: 138594811
Change-Id: Ie440e290dc89b72c46de2194da0275910c03a66d
Signed-off-by: default avatarAshwini Oruganti <ashfall@google.com>
Signed-off-by: default avatarPranav Vashi <neobuddy89@gmail.com>
parent 43192520

Documentation/sysctl/vm.txt

+0 −19
Original line number Diff line number Diff line
@@ -50,7 +50,6 @@ Currently, these files are in /proc/sys/vm: 
- nr_trim_pages         (only if CONFIG_MMU=n)

- numa_zonelist_order

- oom_dump_tasks

- reap_mem_on_sigkill

- oom_kill_allocating_task

- overcommit_kbytes

- overcommit_memory
@@ -658,24 +657,6 @@ The default value is 1 (enabled). 


==============================================================



reap_mem_on_sigkill



This enables or disables the memory reaping for a SIGKILL received

process and that the sending process must have the CAP_KILL capabilities.



If this is set to 1, when a process receives SIGKILL from a process

that has the capability, CAP_KILL, the process is added into the oom_reaper

queue which can be picked up by the oom_reaper thread to reap the memory of

that process. This reaps for the process which received SIGKILL through

either sys_kill from user or kill_pid from kernel.



If this is set to 0, we are not reaping memory of a SIGKILL, sent through

either sys_kill from user or kill_pid from kernel, received process.



The default value is 0 (disabled).



==============================================================



oom_kill_allocating_task



This enables or disables killing the OOM-triggering task in

include/linux/oom.h

+0 −4
Original line number Diff line number Diff line
@@ -123,8 +123,4 @@ extern void wake_oom_reaper(struct task_struct *tsk); 
extern int sysctl_oom_dump_tasks;

extern int sysctl_oom_kill_allocating_task;

extern int sysctl_panic_on_oom;

extern int sysctl_reap_mem_on_sigkill;



/* calls for LMK reaper */

extern void add_to_oom_reaper(struct task_struct *p);

#endif /* _INCLUDE_LINUX_OOM_H */

kernel/signal.c

+1 −6
Original line number Diff line number Diff line
@@ -42,8 +42,6 @@ 
#include <linux/cn_proc.h>

#include <linux/compiler.h>

#include <linux/posix-timers.h>

#include <linux/oom.h>

#include <linux/capability.h>

#include <linux/cgroup.h>



#define CREATE_TRACE_POINTS
@@ -1346,11 +1344,8 @@ int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p) 
	ret = check_kill_permission(sig, info, p);

	rcu_read_unlock();



	if (!ret && sig) {

	if (!ret && sig)

		ret = do_send_sig_info(sig, info, p, true);

		if (capable(CAP_KILL) && sig == SIGKILL)

			add_to_oom_reaper(p);

	}



	return ret;

}

kernel/sysctl.c

+0 −7
Original line number Diff line number Diff line
@@ -1480,13 +1480,6 @@ static struct ctl_table vm_table[] = { 
		.mode		= 0644,

		.proc_handler	= proc_dointvec,

	},

	{

		.procname       = "reap_mem_on_sigkill",

		.data           = &sysctl_reap_mem_on_sigkill,

		.maxlen         = sizeof(sysctl_reap_mem_on_sigkill),

		.mode           = 0644,

		.proc_handler   = proc_dointvec,

	},

	{

		.procname	= "overcommit_ratio",

		.data		= &sysctl_overcommit_ratio,

mm/oom_kill.c

+8 −53
Original line number Diff line number Diff line
@@ -53,7 +53,6 @@ 
int sysctl_panic_on_oom;

int sysctl_oom_kill_allocating_task;

int sysctl_oom_dump_tasks = 1;

int sysctl_reap_mem_on_sigkill;



DEFINE_MUTEX(oom_lock);

/* Serializes oom_score_adj and oom_score_adj_min updates */
@@ -608,21 +607,13 @@ void wake_oom_reaper(struct task_struct *tsk) 
	if (!oom_reaper_th)

		return;



	/*

	 * Move the lock here to avoid scenario of queuing

	 * the same task by both OOM killer and any other SIGKILL

	 * path.

	 */

	spin_lock(&oom_reaper_lock);



	/* mm is already queued? */

	if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags)) {

		spin_unlock(&oom_reaper_lock);

	if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))

		return;

	}



	get_task_struct(tsk);



	spin_lock(&oom_reaper_lock);

	tsk->oom_reaper_list = oom_reaper_list;

	oom_reaper_list = tsk;

	spin_unlock(&oom_reaper_lock);
@@ -647,16 +638,6 @@ static inline void wake_oom_reaper(struct task_struct *tsk) 
}

#endif /* CONFIG_MMU */



static void __mark_oom_victim(struct task_struct *tsk)

{

	struct mm_struct *mm = tsk->mm;



	if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) {

		mmgrab(tsk->signal->oom_mm);

		set_bit(MMF_OOM_VICTIM, &mm->flags);

	}

}



/**

 * mark_oom_victim - mark the given task as OOM victim

 * @tsk: task to mark
@@ -669,13 +650,18 @@ static void __mark_oom_victim(struct task_struct *tsk) 
 */

static void mark_oom_victim(struct task_struct *tsk)

{

	struct mm_struct *mm = tsk->mm;



	WARN_ON(oom_killer_disabled);

	/* OOM killer might race with memcg OOM */

	if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))

		return;



	/* oom_mm is bound to the signal struct life time. */

	__mark_oom_victim(tsk);

	if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) {

		mmgrab(tsk->signal->oom_mm);

		set_bit(MMF_OOM_VICTIM, &mm->flags);

	}



	/*

	 * Make sure that the task is woken up from uninterruptible sleep
@@ -1138,34 +1124,3 @@ void dump_killed_info(struct task_struct *selected) 
			global_node_page_state(NR_FILE_PAGES) *

				(long)(PAGE_SIZE / 1024));

}
 


void add_to_oom_reaper(struct task_struct *p)

{

	static DEFINE_RATELIMIT_STATE(reaper_rs, DEFAULT_RATELIMIT_INTERVAL,

						 DEFAULT_RATELIMIT_BURST);



	if (!sysctl_reap_mem_on_sigkill)

		return;



	p = find_lock_task_mm(p);

	if (!p)

		return;



	get_task_struct(p);

	if (task_will_free_mem(p)) {

		__mark_oom_victim(p);

		wake_oom_reaper(p);

	}



	dump_killed_info(p);

	task_unlock(p);



	if (__ratelimit(&reaper_rs) && p->signal->oom_score_adj == 0) {

		show_mem(SHOW_MEM_FILTER_NODES, NULL);

		show_mem_call_notifiers();

		if (sysctl_oom_dump_tasks)

			dump_tasks(NULL, NULL);

	}



	put_task_struct(p);

}