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

[Simon Horman <horms@kernel.org>]

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.

-- 
pw-bot: changes-requested