path: root/kernel/fork.c
diff options
authorSultan Alsawaf <sultanxda@gmail.com>2018-06-03 10:47:51 -0700
committerGreg Kroah-Hartman <gregkh@google.com>2018-07-18 13:22:08 +0000
commit47bbcd6bf8f926e4e009c12b18f349ffa41bafd4 (patch)
tree0192ec6f7bffd6f95720756d48bcd6a360a56b5a /kernel/fork.c
parent23a1412b82a037482e214ab77a9c73c8218029b4 (diff)
ANDROID: Fix massive cpufreq_times memory leaks
Every time _cpu_up() is called for a CPU, idle_thread_get() is called which then re-initializes a CPU's idle thread that was already previously created and cached in a global variable in smpboot.c. idle_thread_get() calls init_idle() which then calls __sched_fork(). __sched_fork() is where cpufreq_task_times_init() is, and cpufreq_task_times_init() allocates memory for the task struct's time_in_state array. Since idle_thread_get() reuses a task struct instance that was already previously created, this means that every time it calls init_idle(), cpufreq_task_times_init() allocates this array again and overwrites the existing allocation that the idle thread already had. This causes memory to be leaked every time a CPU is onlined. In order to fix this, move allocation of time_in_state into _do_fork to avoid allocating it at all for idle threads. The cpufreq times interface is intended to be used for tracking userspace tasks, so we can safely remove it from the kernel's idle threads without killing any functionality. But that's not all! Task structs can be freed outside of release_task(), which creates another memory leak because a task struct can be freed without having its cpufreq times allocation freed. To fix this, free the cpufreq times allocation at the same time that task struct allocations are freed, in free_task(). Since free_task() can also be called in error paths of copy_process() after dup_task_struct(), set time_in_state to NULL immediately after calling dup_task_struct() to avoid possible double free. Bug description and fix adapted from patch submitted by Sultan Alsawaf <sultanxda@gmail.com> at https://android-review.googlesource.com/c/kernel/msm/+/700134 Bug: 110044919 Test: Hikey960 builds, boots & reports /proc/<pid>/time_in_state correctly Change-Id: I12fe7611fc88eb7f6c39f8f7629ad27b6ec4722c Signed-off-by: Connor O'Brien <connoro@google.com>
Diffstat (limited to 'kernel/fork.c')
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 70e10cb49be0..24ce22c41f21 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -77,6 +77,7 @@
#include <linux/compiler.h>
#include <linux/sysctl.h>
#include <linux/kcov.h>
+#include <linux/cpufreq_times.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -339,6 +340,8 @@ void put_task_stack(struct task_struct *tsk)
void free_task(struct task_struct *tsk)
+ cpufreq_task_times_exit(tsk);
* The task is finally done with both the stack and thread_info,
@@ -1527,6 +1530,8 @@ static __latent_entropy struct task_struct *copy_process(
if (!p)
goto fork_out;
+ cpufreq_task_times_init(p);
@@ -1963,6 +1968,8 @@ long _do_fork(unsigned long clone_flags,
struct completion vfork;
struct pid *pid;
+ cpufreq_task_times_alloc(p);
trace_sched_process_fork(current, p);
pid = get_task_pid(p, PIDTYPE_PID);