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authorAnton Vorontsov <anton.vorontsov@linaro.org>2012-05-31 16:26:25 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-31 17:49:30 -0700
commit137d1a26c842a384c98dd2a6a605014fddf5c777 (patch)
tree615db05121d00f246e1aa5b461f173c54c5391dd /arch
parent9bd0a077122a6b15069aab7a59c8f50f736fa1dd (diff)
downloadlinux-137d1a26c842a384c98dd2a6a605014fddf5c777.tar.gz
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>
Diffstat (limited to 'arch')
-rw-r--r--arch/um/kernel/reboot.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/arch/um/kernel/reboot.c b/arch/um/kernel/reboot.c
index 66d754c46e7..1411f4e79f9 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);