On 9/30/2025 10:29 PM, Przemek Kitszel wrote:
> On 9/30/25 03:51, Haotian Zhang wrote:
>> When ice_adapter_new() fails, the reserved XArray entry created by
>> xa_insert() is not released. This causes subsequent insertions at
>> the same index to return -EBUSY, potentially leading to
>> NULL pointer dereferences.
>>
>> Release the reserved entry with xa_release() when adapter allocation
>> fails to prevent this issue.
>>
>> Fixes: 0f0023c649c7 ("ice: do not init struct ice_adapter more times than
>> needed")
>> Suggested-by: Jacob Keller <[email protected]>
>> Signed-off-by: Haotian Zhang <[email protected]>
>>
>> ---
>> Changes in v2:
>> - Instead of checking the return value of xa_store(), fix the real bug
>> where a failed ice_adapter_new() would leave a stale entry in the
>> XArray.
>> - Use xa_release() to clean up the reserved entry, as suggested by
>> Jacob Keller.
>
> this is a correct improvement, but please let me propose other options,
> with 2. being my favorite:
>
> 1. (just ice changes)
> change the call order to be:
> (note that it is under a mutex)
> xa_load() // return early if another adapter exists
> xa_reserve() // return early if no mem
> ice_adapter_new() // return early if err
You still have to xa_release() here if we return early, but adding the
call to xa_reserve might be more expressive of the intended behavior vs
using xa_insert was.
> xa_store()
>
>
> 2. (xarray changes)
> (perhaps I'm biased as the one introducing the error on error path):
> change xa_insert() to return 0 or -EEXIST when used as a reserving call
> (IOW: caller wanted to reserve, entry is reserved, so return should be 0
> (or -EEXIST if we really want to differentiate in the callers)).
>
If we go this route, I think -EEXIST is the right answer, as it should
only return 0 if *this* call reserved the entry. -EEXIST instead of
-EBUSY could differentiate between "slot is reserved" and "slot is
filled" though.
That would let us fix the issue by having xa_insert differentiate and go
ahead if it fines a reserved entry that was unused. Thats safe for *our*
use case because we know we were under lock and the only way we'd have a
stale reserved entry is if we failed to release it...
I am not certain how other users or maintainer of xarray would feel
about such a change, which makes me think the ice side change is the
best at least initially.
>
>> ---
>> drivers/net/ethernet/intel/ice/ice_adapter.c | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/ethernet/intel/ice/ice_adapter.c
>> b/drivers/net/ethernet/intel/ice/ice_adapter.c
>> index b53561c34708..9eb100b11439 100644
>> --- a/drivers/net/ethernet/intel/ice/ice_adapter.c
>> +++ b/drivers/net/ethernet/intel/ice/ice_adapter.c
>> @@ -110,8 +110,10 @@ struct ice_adapter *ice_adapter_get(struct pci_dev
>> *pdev)
>> return ERR_PTR(err);
>>
>> adapter = ice_adapter_new(pdev);
>> - if (!adapter)
>> + if (!adapter) {
>> + xa_release(&ice_adapters, index);
>> return ERR_PTR(-ENOMEM);
>> + }
>> xa_store(&ice_adapters, index, adapter, GFP_KERNEL);
>> }
>> return adapter;
>
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