5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zhao Li [ Upstream commit a5f35d4b112af1415ff06bd501c8cc26cc08aa8b ] Proxy-path churn can drive the interface path counter negative and let later mesh path additions exceed MESH_MAX_MPATHS. mesh_path_free_rcu() decrements the interface mpaths counter for entries from both the mesh and proxy path tables, but mpp_path_add() never reserves a slot in that counter. Removing or expiring a proxy path therefore returns a slot that was never charged. mesh_path_add() uses the same counter to enforce MESH_MAX_MPATHS, so once it falls below the number of installed paths the limit no longer holds. Reserve the shared quota before allocating a proxy path and release it on every unsuccessful addition. Mesh and proxy paths now share one 1024-entry budget, so mpp_path_add() can return -ENOSPC at that limit. Fixes: ece1a2e7e860 ("mac80211: Remove mesh paths when an interface is removed") Cc: stable@vger.kernel.org Assisted-by: LLM sparse kasan Signed-off-by: Zhao Li Link: https://patch.msgid.link/20260916113649.28315-3-enderaoelyther@gmail.com Signed-off-by: Johannes Berg [ sashal: Adjusted error-handling braces to accommodate the missing mesh_fast_tx_flush_addr() call. ] Signed-off-by: Sasha Levin --- net/mac80211/mesh_pathtbl.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c index a0ef296e3e4f3..f2970f33f96c5 100644 --- a/net/mac80211/mesh_pathtbl.c +++ b/net/mac80211/mesh_pathtbl.c @@ -449,10 +449,15 @@ int mpp_path_add(struct ieee80211_sub_if_data *sdata, if (is_multicast_ether_addr(dst)) return -ENOTSUPP; + if (!atomic_add_unless(&sdata->u.mesh.mpaths, 1, MESH_MAX_MPATHS)) + return -ENOSPC; + new_mpath = mesh_path_new(sdata, dst, GFP_ATOMIC); - if (!new_mpath) + if (!new_mpath) { + atomic_dec(&sdata->u.mesh.mpaths); return -ENOMEM; + } memcpy(new_mpath->mpp, mpp, ETH_ALEN); tbl = &sdata->u.mesh.mpp_paths; @@ -465,8 +470,10 @@ int mpp_path_add(struct ieee80211_sub_if_data *sdata, hlist_add_head_rcu(&new_mpath->walk_list, &tbl->walk_head); spin_unlock_bh(&tbl->walk_lock); - if (ret) + if (ret) { kfree(new_mpath); + atomic_dec(&sdata->u.mesh.mpaths); + } sdata->u.mesh.mpp_paths_generation++; return ret; -- 2.53.0