Kmemleak periodically reports transient false positives for radix tree nodes allocated through the IDR, for example: unreferenced object 0xffff0004d6ac4200 (size 576): comm "tcpeventd", pid 6412 backtrace (crc 335d668a): kmem_cache_alloc_noprof radix_tree_node_alloc radix_tree_extend idr_get_free idr_alloc_cyclic map_create __sys_bpf radix_tree_extend() (grow) and radix_tree_shrink() (shrink) repoint root->xa_head to a new node. If a kmemleak scan has already walked past root->xa_head, the new head is not reachable from any scanned pointer until the following scan, so kmemleak reports it as leaked even though it is live. This is the same race fixed for the XArray API in commit a1a029bcea59 ("XArray: fix kmemleak false positive in xas_shrink()"). The IDR uses the radix tree API directly and hits it on both the grow and the shrink path, so mark the new head as a transient leak in both. Add a matching kmemleak_transient_leak() stub to the radix tree test harness so the userspace lib/radix-tree.c build keeps building. Signed-off-by: Breno Leitao --- Changes in v2: - Add a kmemleak_transient_leak() stub to the radix tree test harness (tools/testing/shared/linux/kmemleak.h) so the userspace lib/radix-tree.c build keeps working; reported by the kernel test robot. - Link to v1: https://lore.kernel.org/r/20260702-radix-tree-v1-1-a87c125b0f96@debian.org To: Andrew Morton Cc: linux-kernel@vger.kernel.org Cc: bpf@vger.kernel.org --- lib/radix-tree.c | 7 ++++++- tools/testing/shared/linux/kmemleak.h | 1 + 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/lib/radix-tree.c b/lib/radix-tree.c index 976b9bd02a1b5..cb5ca920fddb6 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -455,6 +455,8 @@ static int radix_tree_extend(struct radix_tree_root *root, gfp_t gfp, node->slots[0] = (void __rcu *)entry; entry = node_to_entry(node); rcu_assign_pointer(root->xa_head, entry); + /* new head may be missed by an in-progress kmemleak scan */ + kmemleak_transient_leak(node); shift += RADIX_TREE_MAP_SHIFT; } while (shift <= maxshift); out: @@ -495,8 +497,11 @@ static inline bool radix_tree_shrink(struct radix_tree_root *root) if (!node->shift && is_idr(root)) break; - if (radix_tree_is_internal_node(child)) + if (radix_tree_is_internal_node(child)) { entry_to_node(child)->parent = NULL; + /* new head may be missed by an in-progress kmemleak scan */ + kmemleak_transient_leak(entry_to_node(child)); + } /* * We don't need rcu_assign_pointer(), since we are simply diff --git a/tools/testing/shared/linux/kmemleak.h b/tools/testing/shared/linux/kmemleak.h index 155f112786c4f..65a383090fb51 100644 --- a/tools/testing/shared/linux/kmemleak.h +++ b/tools/testing/shared/linux/kmemleak.h @@ -1 +1,2 @@ static inline void kmemleak_update_trace(const void *ptr) { } +static inline void kmemleak_transient_leak(const void *ptr) { } --- base-commit: 840ef6c78e6a2f694b578ecb9063241c992aaa9e change-id: 20260702-radix-tree-8ae41d324101 Best regards, -- Breno Leitao