From a3a2e76c77fa22b114e421ac11dec0c56c3503fb Mon Sep 17 00:00:00 2001
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Date: Tue, 6 Apr 2010 14:34:42 -0700
Subject: [PATCH] mm: avoid null-pointer deref in sync_mm_rss()
- We weren't zeroing p->rss_stat[] at fork()
- Consequently sync_mm_rss() was dereferencing tsk->mm for kernel
threads and was oopsing.
- Make __sync_task_rss_stat() static, too.
Addresses https://bugzilla.kernel.org/show_bug.cgi?id=15648
[akpm@linux-foundation.org: remove the BUG_ON(!mm->rss)]
Reported-by: Troels Liebe Bentsen <tlb@rapanden.dk>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
"Michael S. Tsirkin" <mst@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
kernel/exit.c | 3 ++-
kernel/fork.c | 3 +++
mm/memory.c | 3 +--
3 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/kernel/exit.c b/kernel/exit.c
index cce59cb5ee6a..7f2683a10ac4 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -953,7 +953,8 @@ NORET_TYPE void do_exit(long code)
acct_update_integrals(tsk);
/* sync mm's RSS info before statistics gathering */
- sync_mm_rss(tsk, tsk->mm);
+ if (tsk->mm)
+ sync_mm_rss(tsk, tsk->mm);
group_dead = atomic_dec_and_test(&tsk->signal->live);
if (group_dead) {
hrtimer_cancel(&tsk->signal->real_timer);
diff --git a/kernel/fork.c b/kernel/fork.c
index 4799c5f0e6d0..44b0791b0a2e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1052,6 +1052,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
p->prev_utime = cputime_zero;
p->prev_stime = cputime_zero;
#endif
+#if defined(SPLIT_RSS_COUNTING)
+ memset(&p->rss_stat, 0, sizeof(p->rss_stat));
+#endif
p->default_timer_slack_ns = current->timer_slack_ns;
diff --git a/mm/memory.c b/mm/memory.c
index 1d2ea39260e5..833952d8b74d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -125,13 +125,12 @@ core_initcall(init_zero_pfn);
#if defined(SPLIT_RSS_COUNTING)
-void __sync_task_rss_stat(struct task_struct *task, struct mm_struct *mm)
+static void __sync_task_rss_stat(struct task_struct *task, struct mm_struct *mm)
{
int i;
for (i = 0; i < NR_MM_COUNTERS; i++) {
if (task->rss_stat.count[i]) {
- BUG_ON(!mm);
add_mm_counter(mm, i, task->rss_stat.count[i]);
task->rss_stat.count[i] = 0;
}
--
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