From: Michael J. Ruhl <michael.j.ruhl@xxxxxxxxx>
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@xxxxxxxxxxxxxxx # v4.14.0+
Fixes: f683c80ca68e ("IB/hfi1: Resolve kernel panics by reference counting receive contexts")
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@xxxxxxxxx>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@xxxxxxxxx>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@xxxxxxxxx>
---
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);
