[PATCH rdma-rc] RDMA/mlx5: Fix unsafe xarray access in implicit ODP handling

[PATCH rdma-rc] RDMA/mlx5: Fix unsafe xarray access in implicit ODP handling

[Leon Romanovsky]

From: Or Har-Toov <ohartoov@nvidia.com>

__xa_store() and __xa_erase() were used without holding the proper lock,
which led to a lockdep warning due to unsafe RCPU usage.
This patch replaces them with xa_store() and xa_erase(), which perform
the necessary locking internally.

=============================
WARNING: suspicious RCPU usage
6.14.0-rc7_for_upstream_debug_2025_03_18_15_01 #1 Not tainted
-----------------------------
./include/linux/xarray.h:1211 suspicious rcu_dereference_protected()
usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
3 locks held by kworker/u136:0/219:
    at: process_one_work+0xbe4/0x15f0
    process_one_work+0x75c/0x15f0
    pagefault_mr+0x9a5/0x1390 [mlx5_ib]

stack backtrace:
CPU: 14 UID: 0 PID: 219 Comm: kworker/u136:0 Not tainted
6.14.0-rc7_for_upstream_debug_2025_03_18_15_01 #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
Workqueue: mlx5_ib_page_fault mlx5_ib_eqe_pf_action [mlx5_ib]
Call Trace:
 dump_stack_lvl+0xa8/0xc0
 lockdep_rcu_suspicious+0x1e6/0x260
 xas_create+0xb8a/0xee0
 xas_store+0x73/0x14c0
 __xa_store+0x13c/0x220
 ? xa_store_range+0x390/0x390
 ? spin_bug+0x1d0/0x1d0
 pagefault_mr+0xcb5/0x1390 [mlx5_ib]
 ? _raw_spin_unlock+0x1f/0x30
 mlx5_ib_eqe_pf_action+0x3be/0x2620 [mlx5_ib]
 ? lockdep_hardirqs_on_prepare+0x400/0x400
 ? mlx5_ib_invalidate_range+0xcb0/0xcb0 [mlx5_ib]
 process_one_work+0x7db/0x15f0
 ? pwq_dec_nr_in_flight+0xda0/0xda0
 ? assign_work+0x168/0x240
 worker_thread+0x57d/0xcd0
 ? rescuer_thread+0xc40/0xc40
 kthread+0x3b3/0x800
 ? kthread_is_per_cpu+0xb0/0xb0
 ? lock_downgrade+0x680/0x680
 ? do_raw_spin_lock+0x12d/0x270
 ? spin_bug+0x1d0/0x1d0
 ? finish_task_switch.isra.0+0x284/0x9e0
 ? lockdep_hardirqs_on_prepare+0x284/0x400
 ? kthread_is_per_cpu+0xb0/0xb0
 ret_from_fork+0x2d/0x70
 ? kthread_is_per_cpu+0xb0/0xb0
 ret_from_fork_asm+0x11/0x20

Fixes: d3d930411ce3 ("RDMA/mlx5: Fix implicit ODP use after free")
Signed-off-by: Or Har-Toov <ohartoov@nvidia.com>
Reviewed-by: Patrisious Haddad <phaddad@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 drivers/infiniband/hw/mlx5/odp.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/infiniband/hw/mlx5/odp.c b/drivers/infiniband/hw/mlx5/odp.c
index eaa2f9f5f3a9..f6abd64f07f7 100644
--- a/drivers/infiniband/hw/mlx5/odp.c
+++ b/drivers/infiniband/hw/mlx5/odp.c
@@ -259,8 +259,8 @@ static void destroy_unused_implicit_child_mr(struct mlx5_ib_mr *mr)
 	}
 
 	if (MLX5_CAP_ODP(mr_to_mdev(mr)->mdev, mem_page_fault))
-		__xa_erase(&mr_to_mdev(mr)->odp_mkeys,
-			   mlx5_base_mkey(mr->mmkey.key));
+		xa_erase(&mr_to_mdev(mr)->odp_mkeys,
+			 mlx5_base_mkey(mr->mmkey.key));
 	xa_unlock(&imr->implicit_children);
 
 	/* Freeing a MR is a sleeping operation, so bounce to a work queue */
@@ -532,8 +532,8 @@ static struct mlx5_ib_mr *implicit_get_child_mr(struct mlx5_ib_mr *imr,
 	}
 
 	if (MLX5_CAP_ODP(dev->mdev, mem_page_fault)) {
-		ret = __xa_store(&dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key),
-				 &mr->mmkey, GFP_KERNEL);
+		ret = xa_store(&dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key),
+			       &mr->mmkey, GFP_KERNEL);
 		if (xa_is_err(ret)) {
 			ret = ERR_PTR(xa_err(ret));
 			__xa_erase(&imr->implicit_children, idx);
-- 
2.49.0

Re: [PATCH rdma-rc] RDMA/mlx5: Fix unsafe xarray access in implicit ODP handling

[Jason Gunthorpe]

On Mon, Jun 16, 2025 at 11:17:01AM +0300, Leon Romanovsky wrote:
> From: Or Har-Toov <ohartoov@nvidia.com>
> 
> __xa_store() and __xa_erase() were used without holding the proper lock,
> which led to a lockdep warning due to unsafe RCPU usage.
> This patch replaces them with xa_store() and xa_erase(), which perform
> the necessary locking internally.
> 
> =============================
> WARNING: suspicious RCPU usage
> 6.14.0-rc7_for_upstream_debug_2025_03_18_15_01 #1 Not tainted
> -----------------------------
> ./include/linux/xarray.h:1211 suspicious rcu_dereference_protected()
> usage!
> 
> other info that might help us debug this:
> 
> rcu_scheduler_active = 2, debug_locks = 1
> 3 locks held by kworker/u136:0/219:
>     at: process_one_work+0xbe4/0x15f0
>     process_one_work+0x75c/0x15f0
>     pagefault_mr+0x9a5/0x1390 [mlx5_ib]
> 
> stack backtrace:
> CPU: 14 UID: 0 PID: 219 Comm: kworker/u136:0 Not tainted
> 6.14.0-rc7_for_upstream_debug_2025_03_18_15_01 #1
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
> rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> Workqueue: mlx5_ib_page_fault mlx5_ib_eqe_pf_action [mlx5_ib]
> Call Trace:

Don't work wrap oops messages.. Ignore the checkpatch thing that tells
you to do that.

Applied to for-rc

Thanks,
Jason