linux-kernel - Re: [PATCH 3/5] slab: handle pfmemalloc slabs properly with sheaves

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <aRG2K8YCqCZa2Yfx@hyeyoo>
Date: Mon, 10 Nov 2025 18:53:47 +0900
From: Harry Yoo <harry.yoo@...cle.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...two.org>,
        David Rientjes <rientjes@...gle.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
        kasan-dev@...glegroups.com
Subject: Re: [PATCH 3/5] slab: handle pfmemalloc slabs properly with sheaves

On Wed, Nov 05, 2025 at 10:05:31AM +0100, Vlastimil Babka wrote:
> When a pfmemalloc allocation actually dips into reserves, the slab is
> marked accordingly and non-pfmemalloc allocations should not be allowed
> to allocate from it. The sheaves percpu caching currently doesn't follow
> this rule, so implement it before we expand sheaves usage to all caches.
> 
> Make sure objects from pfmemalloc slabs don't end up in percpu sheaves.
> When freeing, skip sheaves when freeing an object from pfmemalloc slab.
> When refilling sheaves, use __GFP_NOMEMALLOC to override any pfmemalloc
> context - the allocation will fallback to regular slab allocations when
> sheaves are depleted and can't be refilled because of the override.
> 
> For kfree_rcu(), detect pfmemalloc slabs after processing the rcu_sheaf
> after the grace period in __rcu_free_sheaf_prepare() and simply flush
> it if any object is from pfmemalloc slabs.
>
> For prefilled sheaves, try to refill them first with __GFP_NOMEMALLOC
> and if it fails, retry without __GFP_NOMEMALLOC but then mark the sheaf
> pfmemalloc, which makes it flushed back to slabs when returned.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> ---

Reviewed-by: Harry Yoo <harry.yoo@...cle.com>

-- 
Cheers,
Harry / Hyeonggon