evie/android_kernel_oneplus_msm8998
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ANDROID: Avoid taking multiple locks in handle_lmk_event

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Conflicting lock events have been reported resulting from
rcu_read_lock, mmap_sem (in get_cmdline) and  lmk_event_lock.

This CL avoids the possibility of these conditions by moving
handle_lmk_event outside rcu_read_lock and invoking get_cmdline before
lmk_event_lock is taken.

Bug: 133479338, 133829075
Signed-off-by: Jim Blackler <jimblackler@google.com>
Change-Id: Ib3c32587472bd972e3ac108798e2af3f4a5c329a
This commit is contained in:
Jim Blackler 2019-06-13 11:54:36 +01:00
parent bcb576e1a7
commit dd842551d5
1 changed files with 17 additions and 13 deletions
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30
drivers/staging/android/lowmemorykiller.c
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@ -102,6 +102,7 @@ void handle_lmk_event(struct task_struct *selected, short min_score_adj)
struct lmk_event *event;
int res;
long rss_in_pages = -1;
char taskname[MAX_TASKNAME];
struct mm_struct *mm = get_task_mm(selected);
if (mm) {
@ -109,6 +110,17 @@ void handle_lmk_event(struct task_struct *selected, short min_score_adj)
mmput(mm);
}
res = get_cmdline(selected, taskname, MAX_TASKNAME - 1);
/* No valid process name means this is definitely not associated with a
* userspace activity.
*/
if (res <= 0 || res >= MAX_TASKNAME)
return;
taskname[res] = '\0';
spin_lock(&lmk_event_lock);
head = event_buffer.head;
@ -123,18 +135,8 @@ void handle_lmk_event(struct task_struct *selected, short min_score_adj)
events = (struct lmk_event *) event_buffer.buf;
event = &events[head];
res = get_cmdline(selected, event->taskname, MAX_TASKNAME - 1);
memcpy(event->taskname, taskname, res + 1);
/* No valid process name means this is definitely not associated with a
* userspace activity.
*/
if (res <= 0 || res >= MAX_TASKNAME) {
spin_unlock(&lmk_event_lock);
return;
}
event->taskname[res] = '\0';
event->pid = selected->pid;
event->uid = from_kuid_munged(current_user_ns(), task_uid(selected));
if (selected->group_leader)
@ -344,13 +346,15 @@ static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
free);
lowmem_deathpending_timeout = jiffies + HZ;
rem += selected_tasksize;
handle_lmk_event(selected, min_score_adj);
}
lowmem_print(4, "lowmem_scan %lu, %x, return %lu\n",
sc->nr_to_scan, sc->gfp_mask, rem);
rcu_read_unlock();
if (selected)
handle_lmk_event(selected, min_score_adj);
return rem;
}