Re: [PATCH v2] RDMA/uverbs: Make CQ handle mandatory for WQ creation

[sashiko-bot@kernel.org]

> From: Li RongQing <lirongqing@baidu.com>
> 
> UVERBS_ATTR_CREATE_WQ_CQ_HANDLE is declared UA_OPTIONAL in the ioctl
> method definition, so the mandatory attribute bitmap does not enforce
> its presence.  When userspace omits it, uverbs_attr_get_obj() returns
> ERR_PTR(-ENOENT) and the handler stores that error pointer into
> wq_init_attr.cq without validation.
> 
> The bogus cq pointer is then passed to the driver's create_wq callback.
> In the mlx5 case, create_rq() calls to_mcq(init_attr->cq) which applies
> container_of to the ERR_PTR value, producing a near-NULL pointer.  The
> subsequent access in get_rq_ts_format() triggers a kernel NULL pointer
> dereference:
> 
>   BUG: kernel NULL pointer dereference, address: 0000000000000296
>   RIP: 0010:create_rq+0x32/0x550 [mlx5_ib]
>   Call Trace:
>    mlx5_ib_create_wq+0x14a/0x210 [mlx5_ib]
>    ib_uverbs_handler_UVERBS_METHOD_WQ_CREATE+0x1f0/0x320 [ib_uverbs]
>    ib_uverbs_run_method+0x296/0x320 [ib_uverbs]
>    ib_uverbs_cmd_verbs+0x1a0/0x260 [ib_uverbs]
>    ib_uverbs_ioctl+0xa8/0x120 [ib_uverbs]
> 
> A WQ without a CQ was never valid; the legacy write path always required
> one via uobj_get_obj_read() in ib_uverbs_ex_create_wq().  Declare the
> attribute UA_MANDATORY so the uverbs framework rejects the ioctl early
> when the CQ handle is missing, before the handler ever runs.
> 
> Fixes: ef3bc084a8ed ("IB/uverbs: Introduce create/destroy WQ commands over ioctl")
> Signed-off-by: Li RongQing <lirongqing@baidu.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260911021557.2113-1-lirongqing@baidu.com?part=1