CAI Qian reported oom-killer killed all system daemons in his
system at first if he ran fork bomb as root. The problem is,
current logic give them bonus of 3% of system ram. Example,
he has 16GB machine, then root processes have ~500MB oom
immune. It bring us crazy bad result. _all_ processes have
oom-score=1 and then, oom killer ignore process memroy usage
and kill random process. This regression is caused by commit
a63d83f427 (oom: badness heuristic rewrite).
This patch changes select_bad_process() slightly. If oom points == 1,
it's a sign that the system have only root privileged processes or
similar. Thus, select_bad_process() calculate oom badness without
root bonus and select eligible process.
Reported-by: CAI Qian <caiqian@xxxxxxxxxx>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
---
fs/proc/base.c | 2 +-
include/linux/oom.h | 3 ++-
mm/oom_kill.c | 19 +++++++++++++++----
3 files changed, 18 insertions(+), 6 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index d6b0424..b608b69 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -482,7 +482,7 @@ static int proc_oom_score(struct task_struct *task, char *buffer)
read_lock(&tasklist_lock);
if (pid_alive(task)) {
- points = oom_badness(task, NULL, NULL, totalpages);
+ points = oom_badness(task, NULL, NULL, totalpages, 1);
ratio = points * 1000 / totalpages;
}
read_unlock(&tasklist_lock);
diff --git a/include/linux/oom.h b/include/linux/oom.h
index 0f5b588..3dd3669 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -42,7 +42,8 @@ enum oom_constraint {
/* The badness from the OOM killer */
extern unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *mem,
- const nodemask_t *nodemask, unsigned long totalpages);
+ const nodemask_t *nodemask, unsigned long totalpages,
+ int protect_root);
extern int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_flags);
extern void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_flags);
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index ba95870..525e1d2 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -133,7 +133,8 @@ static bool oom_unkillable_task(struct task_struct *p,
* task consuming the most memory to avoid subsequent oom failures.
*/
unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *mem,
- const nodemask_t *nodemask, unsigned long totalpages)
+ const nodemask_t *nodemask, unsigned long totalpages,
+ int protect_root)
{
unsigned long points;
unsigned long score_adj = 0;
@@ -186,7 +187,7 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *mem,
*
* XXX: Too large bonus. Example,if the system have tera-bytes memory...
*/
- if (has_capability_noaudit(p, CAP_SYS_ADMIN)) {
+ if (protect_root && has_capability_noaudit(p, CAP_SYS_ADMIN)) {
if (points >= totalpages / 32)
points -= totalpages / 32;
else
@@ -298,8 +299,10 @@ static struct task_struct *select_bad_process(unsigned long *ppoints,
{
struct task_struct *g, *p;
struct task_struct *chosen = NULL;
+ int protect_root = 1;
*ppoints = 0;
+ retry:
do_each_thread_reverse(g, p) {
unsigned long points;
@@ -345,13 +348,18 @@ static struct task_struct *select_bad_process(unsigned long *ppoints,
}
}
- points = oom_badness(p, mem, nodemask, totalpages);
+ points = oom_badness(p, mem, nodemask, totalpages, protect_root);
if (points > *ppoints) {
chosen = p;
*ppoints = points;
}
} while_each_thread(g, p);
+ if (protect_root && (*ppoints == 1)) {
+ protect_root = 0;
+ goto retry;
+ }
+
return chosen;
}
@@ -470,6 +478,7 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
struct task_struct *child;
struct task_struct *t = p;
unsigned long victim_points = 0;
+ int admin;
if (printk_ratelimit())
dump_header(p, gfp_mask, order, mem, nodemask);
@@ -494,6 +503,8 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
* parent. This attempts to lose the minimal amount of work done while
* still freeing memory.
*/
+ admin = has_capability_noaudit(victim, CAP_SYS_ADMIN);
+ victim_points = oom_badness(victim, mem, nodemask, totalpages, !admin);
do {
list_for_each_entry(child, &t->children, sibling) {
unsigned long child_points;
@@ -504,7 +515,7 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
* oom_badness() returns 0 if the thread is unkillable
*/
child_points = oom_badness(child, mem, nodemask,
- totalpages);
+ totalpages, !admin);
if (child_points > victim_points) {
victim = child;
victim_points = child_points;
--
1.7.3.1
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxxx For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>