-----Original Message----- From: Jason Gunthorpe [mailto:jgg@ziepe.ca] Sent: Thursday, January 17, 2019 4:12 PM To: Dalessandro, Dennis dennis.dalessandro@intel.com Cc: dledford@redhat.com; linux-rdma@vger.kernel.org; Ruhl, Michael J michael.j.ruhl@intel.com; Marciniszyn, Mike mike.marciniszyn@intel.com; stable@vger.kernel.org Subject: Re: [PATCH for-rc 5/7] IB/hfi1: Close race condition on user context disable and close
On Thu, Jan 17, 2019 at 12:41:54PM -0800, Dennis Dalessandro wrote:
From: Michael J. Ruhl michael.j.ruhl@intel.com
When disabling and removing a receive context, it is possible for an asynchronous event (i.e IRQ) to occur. Because of this there is a race between cleaning up the context, and the context being used by the asynchronous event.
cpu 0 (context cleanup) rc->ref_count-- (ref_count == 0) hfi1_rcd_free() cpu 1 (IRQ (with rcd index)) rcd_get_by_index() lock ref_count+++ <-- reference count race (WARNING) return rcd unlock cpu 0 hfi1_free_ctxtdata() <-- incorrect free location lock remove rcd from array unlock free rcd
This race will cause the following WARNING trace:
WARNING: CPU: 0 PID: 175027 at include/linux/kref.h:52
hfi1_rcd_get_by_index+0x84/0xa0 [hfi1]
CPU: 0 PID: 175027 Comm: IMB-MPI1 Kdump: loaded Tainted: G OE -----------
- 3.10.0-957.el7.x86_64 #1
Hardware name: Intel Corporation S2600KP/S2600KP, BIOS
SE5C610.86B.11.01.0076.C4.111920150602 11/19/2015
Call Trace: dump_stack+0x19/0x1b __warn+0xd8/0x100 warn_slowpath_null+0x1d/0x20 hfi1_rcd_get_by_index+0x84/0xa0 [hfi1] is_rcv_urgent_int+0x24/0x90 [hfi1] general_interrupt+0x1b6/0x210 [hfi1] __handle_irq_event_percpu+0x44/0x1c0 handle_irq_event_percpu+0x32/0x80 handle_irq_event+0x3c/0x60 handle_edge_irq+0x7f/0x150 handle_irq+0xe4/0x1a0 do_IRQ+0x4d/0xf0 common_interrupt+0x162/0x162
The race can also lead to a use after free which could be similar to:
general protection fault: 0000 1 SMP CPU: 71 PID: 177147 Comm: IMB-MPI1 Kdump: loaded Tainted: G W OE ------
------ 3.10.0-957.el7.x86_64 #1
Hardware name: Intel Corporation S2600KP/S2600KP, BIOS
SE5C610.86B.11.01.0076.C4.111920150602 11/19/2015
task: ffff9962a8098000 ti: ffff99717a508000 task.ti: ffff99717a508000
__kmalloc+0x94/0x230
Call Trace: ? hfi1_user_sdma_process_request+0x9c8/0x1250 [hfi1] hfi1_user_sdma_process_request+0x9c8/0x1250 [hfi1] hfi1_aio_write+0xba/0x110 [hfi1] do_sync_readv_writev+0x7b/0xd0 do_readv_writev+0xce/0x260 ? handle_mm_fault+0x39d/0x9b0 ? pick_next_task_fair+0x5f/0x1b0 ? sched_clock_cpu+0x85/0xc0 ? __schedule+0x13a/0x890 vfs_writev+0x35/0x60 SyS_writev+0x7f/0x110 system_call_fastpath+0x22/0x27
Introduce a context enable flag to indicate if the context is enabled.
Reorder context cleanup to ensure context removal before cleanup occurs correctly.
Cc: stable@vger.kernel.org # v4.14.0+ Fixes: f683c80ca68e ("IB/hfi1: Resolve kernel panics by reference counting
receive contexts")
Reviewed-by: Mike Marciniszyn mike.marciniszyn@intel.com Signed-off-by: Michael J. Ruhl michael.j.ruhl@intel.com Signed-off-by: Dennis Dalessandro dennis.dalessandro@intel.com drivers/infiniband/hw/hfi1/file_ops.c | 2 ++ drivers/infiniband/hw/hfi1/hfi.h | 3 ++- drivers/infiniband/hw/hfi1/init.c | 8 +++++--- 3 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/drivers/infiniband/hw/hfi1/file_ops.c
b/drivers/infiniband/hw/hfi1/file_ops.c
index c22ebc7..0ba0cf5 100644 +++ b/drivers/infiniband/hw/hfi1/file_ops.c @@ -671,6 +671,8 @@ static int hfi1_file_close(struct inode *inode, struct
file *fp)
} spin_unlock_irqrestore(&dd->uctxt_lock, flags);
- uctxt->del_pend = 1;
Not going to get good results if you update shared data outside the lock that is reading it..
@@ -326,7 +325,10 @@ struct hfi1_ctxtdata *hfi1_rcd_get_by_index(struct
hfi1_devdata *dd, u16 ctxt)
spin_lock_irqsave(&dd->uctxt_lock, flags); if (dd->rcd[ctxt]) { rcd = dd->rcd[ctxt];
hfi1_rcd_get(rcd);
if (rcd->del_pend)rcd = NULL;elsehfi1_rcd_get(rcd);This probably wants to be kref_get_not_zero() - why add a confusing del_pend?
kref_get_unless_zero()?
/sigh. I missed that function completely.
I will examine this some more and work up a new patch.
M
Jason