From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793182017; b=t3fgGiOg72RwQ5x75wmjzp/XMzjyHSgrbpS1Wln24ccbXu4ThkpVewyb6eBoDaAYExR5 8XY4XDWiu3NmQt3bEsrpWlG0qwqx5/QFrDklVovperdmI7iHCh5Pv0/GXoff32FesgCQP 6/DetOb5BE9TtlXX9L3a6QbLnCEVGmottwNrTMVzYfnJmtjSt3gB0+IkmQxfhE9zdNR/z JcywGqarLJcTQI4wTuEjWqQLcmhW1ReJkVmSaePq1jZHJeVZYgFX5oyGilBNUbEAhQW77 v3LPL0vJUfdkX1KEkL6+kh0rL14WDNqocmcy6KCPjMaZS94lMxgJppCFYqOHrSkO/4Q== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793182017; h=Received:DKIM-Signature:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:From:Content-Language:Autocrypt:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=aMKBLsxYHUnbIfVjoYx3Vq17ZceYoUGDZhH0VX3zlo4=; b=3N+CCJX3Babbo2LbkE7QmWOGdzWc8WbTPouiQ0XZMkG6pf/DFbGrvOvJWVXqrNyDTZB8 C18C8F2cnm2H2wvAz/4kG4YmbwBjtj4oR/JP0e/tegTg2BOLdo6A9B/UAicBJ/rrDzirb Y7T4CbPz/t5PgWrEVyNPFh0cMzAGjsMfgjKB+NIemUs/xtSwmCLqNddvu8KSbolJ/MrDM xT7WafEvO3xhY1HAKY1ecQcpLlSKcvTMcixWJXbXMz9JNrvY4ZFxwQpHcVcLup9dDEse5 B877cPz3HrbVND8TB5J+jUZ7VpMSNxHF+CVLNjcyOkwjPegRjUyOcfcvJ6y9eF9eWtA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="c/cVKUWw"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5DE3D606A31A; Wed, 28 Oct 2026 10:06:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=c/cVKUWw Received: by smtp.kernel.org (Postfix) with ESMTPSA id 674FE1F01825; Wed, 28 Oct 2026 10:06:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793182017; bh=aMKBLsxYHUnbIfVjoYx3Vq17ZceYoUGDZhH0VX3zlo4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=c/cVKUWwvHQlXN8u4cB6G6LD5VOsTXkW1mYttiSFtfYQOC8o6gttQiR/PM29yMxre retigVXoKJ0F5JJV4gU29i4c5I8lxwG24QQOku1iOAaPHnINtOyviaNmPdB3cihQ+r wplgUCifRTKChtG7AS25gs2Cc31HDdxs+utyIqtN6UWTL+Su+Hg4DWIuUuz3tdvk37 S6dAoU+2qxiJBWwT3CkJPokw3/yMy5yTf2Bo4s9TqXC3MNAGSmNypMdYE/dcdJxfMW rUzy71vmkFD+RmCUeyTTEUPa/4Y/3gNmOAilwn8aH0wiVczPw0scLV+4C3gMLftYC2 F7YXslqJKpYGg== Message-ID: <11c6fd13-d2a2-4497-8417-d2176f1b5ecf@kernel.org> Date: Wed, 28 Oct 2026 11:06:46 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 01/15] mm/mempolicy: charge shared policy nodes To: Balbir Singh Cc: Andrew Morton , Gregory Price , Zi Yan , Joshua Hahn , Rakie Kim , Ying Huang , Johannes Weiner , Vladimir Davydov , Michal Hocko , Hugh Dickins , Baolin Wang , Lukas Czerner , Carlos Maiolino , Christian Brauner , Jan Kara , Daniel Verkamp , Jeff Xu , Muchun Song , Oscar Salvador , David Stevens , "Matthew Wilcox (Oracle)" , William Kucharski , Chris Li , Kairui Song , Nhat Pham , Miaohe Lin , Naoya Horiguchi , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Chris Mason , stable@vger.kernel.org, Pedro Falcato , "Kiryl Shutsemau (Meta)" References: <20261028-fixes_shmem-v3-0-4ce3baf2db4b@kernel.org> <20261028-fixes_shmem-v3-1-4ce3baf2db4b@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/28/26 11:02, Balbir Singh wrote: > On Wed, Oct 28, 2026 at 10:54:59AM +0100, David Hildenbrand (Arm) wrote: >> From: Chris Mason >> >> Any local user can bypass memory.max with mbind() on a tmpfs file, and >> allocate unbounded kernel memory. >> >> mbind() sets a NUMA memory policy for a range of a mapping. If the >> mapping is of a shmem and friends, the kernel also stores the policy on >> the inode, in a tree with one entry per range of the file. >> >> Each mbind() on a single page of a mapping can add one shared policy node >> (struct sp_node) and one struct mempolicy to that tree. They outlive the >> mapping and stay around until the inode is destroyed. The tree is not >> bounded by the file size, so the file can be empty. >> >> Memory that user space can allocate must be charged to a memory cgroup. A >> slab cache does that for all of its objects if it is created with >> SLAB_ACCOUNT. numa_policy_init() creates the slab caches for both >> structs without SLAB_ACCOUNT, so they are not charged to any cgroup. >> >> Reproduced with mbind() on single pages of an empty tmpfs file, from a >> cgroup with memory.max=8M: the global OOM killer killed tasks owned by >> root, and the machine panicked. >> >> Fix this by creating both caches with SLAB_ACCOUNT. This change implies >> that mbind() can now fail when running into memcg limits. Further, >> the policy_cache also serves task and VMA policies, so they are >> similarly accounted now. >> >> Note that per-file limits are not really helpful, as the user could >> simply use many files; having limits per user is tricky as well. >> >> Fix generated by an LLM and submitted by Chris Mason in private. >> >> Fixes: 5d097056c9a0 ("kmemcg: account certain kmem allocations to memcg") >> Cc: stable@vger.kernel.org >> Signed-off-by: Chris Mason >> Acked-by: Pedro Falcato >> Acked-by: Kiryl Shutsemau (Meta) >> Acked-by: Zi Yan >> Reviewed-by: Baolin Wang >> Tested-by: Gregory Price (Meta) >> [ david: smaller description tweaks ] >> Signed-off-by: David Hildenbrand (Arm) >> --- >> mm/mempolicy.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/mm/mempolicy.c b/mm/mempolicy.c >> index 0884c629670d..4da1cb8777f6 100644 >> --- a/mm/mempolicy.c >> +++ b/mm/mempolicy.c >> @@ -3372,11 +3372,11 @@ void __init numa_policy_init(void) >> >> policy_cache = kmem_cache_create("numa_policy", >> sizeof(struct mempolicy), >> - 0, SLAB_PANIC, NULL); >> + 0, SLAB_PANIC | SLAB_ACCOUNT, NULL); >> >> sn_cache = kmem_cache_create("shared_policy_node", >> sizeof(struct sp_node), >> - 0, SLAB_PANIC, NULL); >> + 0, SLAB_PANIC | SLAB_ACCOUNT, NULL); >> >> for_each_node(nid) { >> preferred_node_policy[nid] = (struct mempolicy) { >> > > You have many of them already, but anyway > > Reviewed-by: Balbir Singh I love it, thanks to all of you :) -- Cheers, David