The patch titled
Subject: um: fix possible race on task->mm
has been removed from the -mm tree. Its filename was
um-fix-possible-race-on-task-mm.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
From: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Richard Weinberger <richard@xxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/um/kernel/reboot.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff -puN arch/um/kernel/reboot.c~um-fix-possible-race-on-task-mm arch/um/kernel/reboot.c
--- a/arch/um/kernel/reboot.c~um-fix-possible-race-on-task-mm
+++ a/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);
_
Patches currently in -mm which might be from anton.vorontsov@xxxxxxxxxx are
origin.patch
um-properly-check-all-process-threads-for-a-live-mm.patch
kernel-cpuc-document-clear_tasks_mm_cpumask.patch
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