On Mon, Mar 11, 2019 at 01:02:29PM +0300, Konstantin Khlebnikov wrote:

free_user() could be called in atomic context.

This patch uses non-sleeping cleanup_srcu_struct_quiesced(). At this stage atomic refcount is zero, thus all read-sections should have been ended.

Thanks, I have this in my tree.

-corey

Example:

BUG: sleeping function called from invalid context at kernel/workqueue.c:2856 in_atomic(): 1, irqs_disabled(): 0, pid: 177, name: ksoftirqd/27 CPU: 27 PID: 177 Comm: ksoftirqd/27 Not tainted 4.19.25-3 #1 Hardware name: AIC 1S-HV26-08/MB-DPSB04-06, BIOS IVYBV060 10/21/2015 Call Trace: dump_stack+0x5c/0x7b ___might_sleep+0xec/0x110 __flush_work+0x48/0x1f0 ? try_to_del_timer_sync+0x4d/0x80 _cleanup_srcu_struct+0x104/0x140 free_user+0x18/0x30 [ipmi_msghandler] ipmi_free_recv_msg+0x3a/0x50 [ipmi_msghandler] deliver_response+0xbd/0xd0 [ipmi_msghandler] deliver_local_response+0xe/0x30 [ipmi_msghandler] handle_one_recv_msg+0x163/0xc80 [ipmi_msghandler] ? dequeue_entity+0xa0/0x960 handle_new_recv_msgs+0x15c/0x1f0 [ipmi_msghandler] tasklet_action_common.isra.22+0x103/0x120 __do_softirq+0xf8/0x2d7 run_ksoftirqd+0x26/0x50 smpboot_thread_fn+0x11d/0x1e0 kthread+0x103/0x140 ? sort_range+0x20/0x20 ? kthread_destroy_worker+0x40/0x40 ret_from_fork+0x1f/0x40

Fixes: 77f8269606bf ("ipmi: fix use-after-free of user->release_barrier.rda") Signed-off-by: Konstantin Khlebnikov khlebnikov@yandex-team.ru Cc: stable@vger.kernel.org # 4.18 Cc: Yang Yingliang yangyingliang@huawei.com Cc: Corey Minyard cminyard@mvista.com

---

drivers/char/ipmi/ipmi_msghandler.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c index e8ba67834746..c35f2bcbaa23 100644 --- a/drivers/char/ipmi/ipmi_msghandler.c +++ b/drivers/char/ipmi/ipmi_msghandler.c @@ -1260,7 +1260,12 @@ EXPORT_SYMBOL(ipmi_get_smi_info); static void free_user(struct kref *ref) { struct ipmi_user *user = container_of(ref, struct ipmi_user, refcount);

• cleanup_srcu_struct(&user->release_barrier);

• /*

• * Cleanup without waiting. This could be called in atomic context.
  

• * Refcount is zero: all read-sections should have been ended.
  

• */
  

• cleanup_srcu_struct_quiesced(&user->release_barrier); kfree(user);

}