From f85acd81aa623e3dcf268c90e5cd8ecf36830984 Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Tue, 9 Nov 2010 21:26:56 +0100 Subject: [PATCH] ioprio: rcu_read_lock/unlock protect find_task_by_vpid call (V2) Commit 4221a9918e38b7494cee341dda7b7b4bb8c04bde "Add RCU check for find_task_by_vpid()" introduced rcu_lockdep_assert to find_task_by_pid_ns= Assertion failed in sys_ioprio_get. The patch is fixing assertion failure in ioprio_set as well. kernel/pid.c:419 invoked rcu_dereference_check() without protection! stack backtrace: Pid: 4254, comm: iotop Not tainted Call Trace: [] lockdep_rcu_dereference+0xaa/0xb2 [] find_task_by_pid_ns+0x4f/0x68 [] find_task_by_vpid+0x1d/0x1f [] sys_ioprio_get+0x50/0x2da [] system_call_fastpath+0x16/0x1b V2: rcu critical section expanded according to comment by Paul E. McKenney Signed-off-by: Sergey Senozhatsky Acked-by: Paul E. McKenney Signed-off-by: Jens Axboe --- fs/ioprio.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/ioprio.c b/fs/ioprio.c index 8def14e24c37..2f7d05c89922 100644 --- a/fs/ioprio.c +++ b/fs/ioprio.c @@ -111,12 +111,14 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio) read_lock(&tasklist_lock); switch (which) { case IOPRIO_WHO_PROCESS: + rcu_read_lock(); if (!who) p = current; else p = find_task_by_vpid(who); if (p) ret = set_task_ioprio(p, ioprio); + rcu_read_unlock(); break; case IOPRIO_WHO_PGRP: if (!who) @@ -205,12 +207,14 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who) read_lock(&tasklist_lock); switch (which) { case IOPRIO_WHO_PROCESS: + rcu_read_lock(); if (!who) p = current; else p = find_task_by_vpid(who); if (p) ret = get_task_ioprio(p); + rcu_read_unlock(); break; case IOPRIO_WHO_PGRP: if (!who) -- 2.20.1