Re: + radix-tree-fix-kmemleak-false-positives-on-tree-head-reassignment.patch added to mm-new branch

[Matthew Wilcox <willy@infradead.org>]

On Sat, Jul 04, 2026 at 07:12:40PM -0700, Andrew Morton wrote:
> The patch titled
>      Subject: radix-tree: fix kmemleak false positives on tree head reassignment
> has been added to the -mm mm-new branch.  Its filename is
>      radix-tree-fix-kmemleak-false-positives-on-tree-head-reassignment.patch

Umm.  I don't see this patch in my inbox anywhere else.  Is email broken
again?

> From: Breno Leitao <leitao@debian.org>
> Subject: radix-tree: fix kmemleak false positives on tree head reassignment
> Date: Fri, 03 Jul 2026 08:22:03 -0700
> 
> 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

This commit ID doesn't exist in any tree I have.

> ("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.

Last time this was proposed, the suggestion was that kmemleak needed to
be fixed.

https://lore.kernel.org/all/aCyI8T2sWlPLEYZ_@arm.com/