diff options
| author | Eric Dumazet <edumazet@google.com> | 2015-11-24 11:39:54 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-11-24 12:03:55 -0800 |
| commit | 81b1a832d79749058863cffe2c0ed4ef40f6e6ec (patch) | |
| tree | 122c100882d738e0d08d377e9780a1d38ea70352 | |
| parent | 4ce01c518ebf6e3818abf5f4a9e1a1ef9d52f232 (diff) | |
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>
| -rw-r--r-- | kernel/pid.c | 4 |
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(); |