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authorEric Dumazet <edumazet@google.com>2015-11-24 11:39:54 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2015-11-24 12:03:55 -0800
commit81b1a832d79749058863cffe2c0ed4ef40f6e6ec (patch)
tree122c100882d738e0d08d377e9780a1d38ea70352 /kernel/pid.c
parent4ce01c518ebf6e3818abf5f4a9e1a1ef9d52f232 (diff)
downloadlinux-81b1a832d79749058863cffe2c0ed4ef40f6e6ec.tar.gz
pidns: fix NULL dereference in __task_pid_nr_ns()
I got a crash during a "perf top" session that was caused by a race in __task_pid_nr_ns() : pid_nr_ns() was inlined, but apparently compiler chose to read task->pids[type].pid twice, and the pid->level dereference crashed because we got a NULL pointer at the second read : if (pid && ns->level <= pid->level) { // CRASH Just use RCU API properly to solve this race, and not worry about "perf top" crashing hosts :( get_task_pid() can benefit from same fix. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/pid.c')
-rw-r--r--kernel/pid.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/pid.c b/kernel/pid.c
index ca368793808e..78b3d9f80d44 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -467,7 +467,7 @@ struct pid *get_task_pid(struct task_struct *task, enum pid_type type)
rcu_read_lock();
if (type != PIDTYPE_PID)
task = task->group_leader;
- pid = get_pid(task->pids[type].pid);
+ pid = get_pid(rcu_dereference(task->pids[type].pid));
rcu_read_unlock();
return pid;
}
@@ -528,7 +528,7 @@ pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
if (likely(pid_alive(task))) {
if (type != PIDTYPE_PID)
task = task->group_leader;
- nr = pid_nr_ns(task->pids[type].pid, ns);
+ nr = pid_nr_ns(rcu_dereference(task->pids[type].pid), ns);
}
rcu_read_unlock();