From: "EunTaik Lee" <eun.taik.lee@samsung.com>
To: "mingo@redhat.com" <mingo@redhat.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: [PATCH] sched/pid fix use-after free in task_tgid_vnr
Date: Fri, 09 Dec 2016 09:33:51 +0000 [thread overview]
Message-ID: <20161209093351epcms1p418673c3cdec7d4c3e81b5df131173c57@epcms1p4> (raw)
In-Reply-To: CGME20161209093351epcms1p418673c3cdec7d4c3e81b5df131173c57@epcms1p4
[-- Attachment #1: Type: text/plain, Size: 1413 bytes --]
There is a use-after-free case with below call stack.
pid_nr_ns+0x10/0x38
cgroup_pidlist_start+0x144/0x400
cgroup_seqfile_start+0x1c/0x24
kernfs_seq_start+0x54/0x90
seq_read+0x15c/0x3a8
kernfs_fop_read+0x38/0x160
__vfs_read+0x28/0xc8
vfs_read+0x84/0xfc
A task in the cg_list was dying and the group_leader's
task struct was already freed.
To avoid this task_tgid_vnr needs to take the
rcu_read_lock and check for pid_alive.
Signed-off-by: Eun Taik Lee <eun.taik.lee@samsung.com>
---
include/linux/sched.h | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index e9c009d..ed567bc 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2118,14 +2118,21 @@ static inline pid_t task_tgid_nr(struct task_struct *tsk)
}
pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns);
+static inline int pid_alive(const struct task_struct *p);
static inline pid_t task_tgid_vnr(struct task_struct *tsk)
{
- return pid_vnr(task_tgid(tsk));
+ pid_t pid = 0;
+
+ rcu_read_lock();
+ if (pid_alive(tsk))
+ pid = pid_vnr(task_tgid(tsk));
+ rcu_read_unlock();
+
+ return pid;
}
-static inline int pid_alive(const struct task_struct *p);
static inline pid_t task_ppid_nr_ns(const struct task_struct *tsk, struct pid_namespace *ns)
{
pid_t pid = 0;
--
1.9.1
next parent reply other threads:[~2016-12-09 9:33 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20161209093351epcms1p418673c3cdec7d4c3e81b5df131173c57@epcms1p4>
2016-12-09 9:33 ` EunTaik Lee [this message]
2016-12-09 17:21 ` [PATCH] sched/pid fix use-after free in task_tgid_vnr Oleg Nesterov
2016-12-09 22:21 ` Eric W. Biederman
2016-12-12 13:46 ` Oleg Nesterov
2016-12-12 19:10 ` Eric W. Biederman
2016-12-13 16:03 ` Oleg Nesterov
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