Messages in this thread Patch in this message | | | Date | Tue, 7 Feb 2012 10:51:41 +0400 | From | Anton Vorontsov <> | Subject | [PATCH 8/8] um: Fix possible race on task->mm |
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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.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org> --- arch/um/kernel/reboot.c | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-)
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); -- 1.7.7.6
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