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
Use the appropriate kref API to verify access.
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
--- Changes since v1: adjust to use kref_get_unless_zero() instead of a flag --- drivers/infiniband/hw/hfi1/hfi.h | 2 +- drivers/infiniband/hw/hfi1/init.c | 14 +++++++++----- 2 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/drivers/infiniband/hw/hfi1/hfi.h b/drivers/infiniband/hw/hfi1/hfi.h index 6582184..048b5d7 100644 --- a/drivers/infiniband/hw/hfi1/hfi.h +++ b/drivers/infiniband/hw/hfi1/hfi.h @@ -1455,7 +1455,7 @@ void hfi1_init_pportdata(struct pci_dev *pdev, struct hfi1_pportdata *ppd, struct hfi1_devdata *dd, u8 hw_pidx, u8 port); void hfi1_free_ctxtdata(struct hfi1_devdata *dd, struct hfi1_ctxtdata *rcd); int hfi1_rcd_put(struct hfi1_ctxtdata *rcd); -void hfi1_rcd_get(struct hfi1_ctxtdata *rcd); +int hfi1_rcd_get(struct hfi1_ctxtdata *rcd); struct hfi1_ctxtdata *hfi1_rcd_get_by_index_safe(struct hfi1_devdata *dd, u16 ctxt); struct hfi1_ctxtdata *hfi1_rcd_get_by_index(struct hfi1_devdata *dd, u16 ctxt); diff --git a/drivers/infiniband/hw/hfi1/init.c b/drivers/infiniband/hw/hfi1/init.c index 7841a0a..2cc5164 100644 --- a/drivers/infiniband/hw/hfi1/init.c +++ b/drivers/infiniband/hw/hfi1/init.c @@ -214,12 +214,12 @@ static void hfi1_rcd_free(struct kref *kref) struct hfi1_ctxtdata *rcd = container_of(kref, struct hfi1_ctxtdata, kref);
- hfi1_free_ctxtdata(rcd->dd, rcd); - spin_lock_irqsave(&rcd->dd->uctxt_lock, flags); rcd->dd->rcd[rcd->ctxt] = NULL; spin_unlock_irqrestore(&rcd->dd->uctxt_lock, flags);
+ hfi1_free_ctxtdata(rcd->dd, rcd); + kfree(rcd); }
@@ -242,10 +242,13 @@ int hfi1_rcd_put(struct hfi1_ctxtdata *rcd) * @rcd: pointer to an initialized rcd data structure * * Use this to get a reference after the init. + * + * Return : reflect kref_get_unless_zero(), which returns non-zero on + * increment, otherwise 0. */ -void hfi1_rcd_get(struct hfi1_ctxtdata *rcd) +int hfi1_rcd_get(struct hfi1_ctxtdata *rcd) { - kref_get(&rcd->kref); + return kref_get_unless_zero(&rcd->kref); }
/** @@ -325,7 +328,8 @@ 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 (!hfi1_rcd_get(rcd)) + rcd = NULL; } spin_unlock_irqrestore(&dd->uctxt_lock, flags);