xavi/android_kernel_m2note/kernel/pid.c, branch o-8.1

pidns: fix NULL dereference in __task_pid_nr_ns()

2019-05-02T15:32:33+00:00

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 Signed-off-by: Linus Torvalds

BACKPORT: FROMLIST: pids: make task_tgid_nr_ns() safe

2017-08-25T18:37:41+00:00

This was reported many times, and this was even mentioned in commit 52ee2dfdd4f5 "pids: refactor vnr/nr_ns helpers to make them safe" but somehow nobody bothered to fix the obvious problem: task_tgid_nr_ns() is not safe because task->group_leader points to nowhere after the exiting task passes exit_notify(), rcu_read_lock() can not help. We really need to change __unhash_process() to nullify group_leader, parent, and real_parent, but this needs some cleanups. Until then we can turn task_tgid_nr_ns() into another user of __task_pid_nr_ns() and fix the problem. Reported-by: Troy Kensinger Signed-off-by: Oleg Nesterov Acked-by: Peter Zijlstra (Intel) (url: https://patchwork.kernel.org/patch/9913055/) Bug: 31495866 Change-Id: I5e67b02a77e805f71fa3a787249f13c1310f02e2

first commit

2016-08-15T02:19:42+00:00