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

[Simon Horman <horms@kernel.org>]

On Wed, Apr 15, 2026 at 10:35:19PM -0700, Yuan Tan wrote:
> 
> 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?

I don't think you should include a Suggested-by tag.

My reasoning is that I'm only providing feedback and possible enhancements
to your approach.  While I think Suggested-by would be appropriate if I'd
suggested creating this patch in the first place.