Re: [PATCH net 1/1] 8021q: free cleared egress QoS mappings safely

[Yuan Tan <yuantan098@gmail.com>]

On 4/15/26 08:15, Simon Horman wrote:
> On Mon, Apr 13, 2026 at 05:07:20PM +0800, Ren Wei wrote:
>> From: Longxuan Yu <ylong030@ucr.edu>
>>
>> vlan_dev_set_egress_priority() leaves cleared egress priority mapping
>> nodes in the hash until device teardown. Repeated set/clear cycles with
>> distinct skb priorities therefore allocate an unbounded number of
>> vlan_priority_tci_mapping objects and leak memory.
>>
>> Delete mappings when vlan_prio is cleared instead of keeping
>> tombstones. The TX fast path and reporting paths walk the lists without
>> RTNL, so convert the egress mapping lists to RCU-protected pointers and
>> defer freeing removed nodes until after a grace period.
>>
>> Cc: stable@kernel.org
>> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>> Reported-by: Yifan Wu <yifanwucs@gmail.com>
>> Reported-by: Juefei Pu <tomapufckgml@gmail.com>
>> Co-developed-by: Yuan Tan <yuantan098@gmail.com>
>> Signed-off-by: Yuan Tan <yuantan098@gmail.com>
>> Suggested-by: Xin Liu <bird@lzu.edu.cn>
>> Signed-off-by: Longxuan Yu <ylong030@ucr.edu>
>> Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
>> ---
>>  include/linux/if_vlan.h  | 23 +++++++++++--------
>>  net/8021q/vlan_dev.c     | 48 +++++++++++++++++++++++-----------------
>>  net/8021q/vlan_netlink.c |  9 +++-----
>>  net/8021q/vlanproc.c     | 12 ++++++----
>>  4 files changed, 53 insertions(+), 39 deletions(-)
> There is a lot of change here. And I'd suggest splitting the patch up into
> (at least) two patches:
>
> 1. Convert mappings to use RCU
> 2. Fix bug
>
> As is, the bug fix itself is difficult to isolate amongst the other changes.
>
> Also, AI generated review suggests that this bug was introduced by commit
> b020cb488586 ("[VLAN]: Keep track of number of QoS mappings"). If so,
> it would be appropriate to use that commit in the Fixes tag.
>
Thank you very much for your review and suggestions. We will try to
revise it in this direction.
May I ask whether we should include your “Suggested-by” tag in the patch?