From 9bd0a077122a6b15069aab7a59c8f50f736fa1dd Mon Sep 17 00:00:00 2001
From: Anton Vorontsov <anton.vorontsov@linaro.org>
Date: Thu, 31 May 2012 16:26:25 -0700
Subject: um: should hold tasklist_lock while traversing processes
Traversing the tasks requires holding tasklist_lock, otherwise it is
unsafe.
p.s. However, I'm not sure that calling os_kill_ptraced_process() in the
atomic context is correct. It seem to work, but please take a closer
look.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
arch/um/kernel/reboot.c | 3 +++
1 file changed, 3 insertions(+)
(limited to 'arch/um/kernel/reboot.c')
diff --git a/arch/um/kernel/reboot.c b/arch/um/kernel/reboot.c
index 4d93dff..66d754c 100644
--- a/arch/um/kernel/reboot.c
+++ b/arch/um/kernel/reboot.c
@@ -4,6 +4,7 @@
*/
#include "linux/sched.h"
+#include "linux/spinlock.h"
#include "linux/slab.h"
#include "kern_util.h"
#include "os.h"
@@ -22,6 +23,7 @@ static void kill_off_processes(void)
struct task_struct *p;
int pid;
+ read_lock(&tasklist_lock);
for_each_process(p) {
if (p->mm == NULL)
continue;
@@ -29,6 +31,7 @@ static void kill_off_processes(void)
pid = p->mm->context.id.u.pid;
os_kill_ptraced_process(pid, 1);
}
+ read_unlock(&tasklist_lock);
}
}
--
cgit v1.1
From 137d1a26c842a384c98dd2a6a605014fddf5c777 Mon Sep 17 00:00:00 2001
From: Anton Vorontsov <anton.vorontsov@linaro.org>
Date: Thu, 31 May 2012 16:26:25 -0700
Subject: um: fix possible race on task->mm
Checking for task->mm is dangerous as ->mm might disappear (exit_mm()
assigns NULL under task_lock(), so tasklist lock is not enough).
We can't use get_task_mm()/mmput() pair as mmput() might sleep, so let's
take the task lock while we care about its mm.
Note that we should also use find_lock_task_mm() to check all process'
threads for a valid mm, but for uml we'll do it in a separate patch.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
arch/um/kernel/reboot.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
(limited to 'arch/um/kernel/reboot.c')
diff --git a/arch/um/kernel/reboot.c b/arch/um/kernel/reboot.c
index 66d754c..1411f4e 100644
--- a/arch/um/kernel/reboot.c
+++ b/arch/um/kernel/reboot.c
@@ -25,10 +25,13 @@ static void kill_off_processes(void)
read_lock(&tasklist_lock);
for_each_process(p) {
- if (p->mm == NULL)
+ task_lock(p);
+ if (!p->mm) {
+ task_unlock(p);
continue;
-
+ }
pid = p->mm->context.id.u.pid;
+ task_unlock(p);
os_kill_ptraced_process(pid, 1);
}
read_unlock(&tasklist_lock);
--
cgit v1.1
From 2c922c51e6924298f8271d75732964f1ffdecaf2 Mon Sep 17 00:00:00 2001
From: Anton Vorontsov <anton.vorontsov@linaro.org>
Date: Thu, 31 May 2012 16:26:26 -0700
Subject: um: properly check all process' threads for a live mm
kill_off_processes() might miss a valid process, this is because checking
for process->mm is not enough. Process' main thread may exit or detach
its mm via use_mm(), but other threads may still have a valid mm.
To catch this we use find_lock_task_mm(), which walks up all threads and
returns an appropriate task (with task lock held).
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: Richard Weinberger <richard@nod.at>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
arch/um/kernel/reboot.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
(limited to 'arch/um/kernel/reboot.c')
diff --git a/arch/um/kernel/reboot.c b/arch/um/kernel/reboot.c
index 1411f4e..3d15243 100644
--- a/arch/um/kernel/reboot.c
+++ b/arch/um/kernel/reboot.c
@@ -6,6 +6,7 @@
#include "linux/sched.h"
#include "linux/spinlock.h"
#include "linux/slab.h"
+#include "linux/oom.h"
#include "kern_util.h"
#include "os.h"
#include "skas.h"
@@ -25,13 +26,13 @@ static void kill_off_processes(void)
read_lock(&tasklist_lock);
for_each_process(p) {
- task_lock(p);
- if (!p->mm) {
- task_unlock(p);
+ struct task_struct *t;
+
+ t = find_lock_task_mm(p);
+ if (!t)
continue;
- }
- pid = p->mm->context.id.u.pid;
- task_unlock(p);
+ pid = t->mm->context.id.u.pid;
+ task_unlock(t);
os_kill_ptraced_process(pid, 1);
}
read_unlock(&tasklist_lock);
--
cgit v1.1